Life Science

C H A P T E R

4 Life Science 4-0.0 Introduction Consult any dictionary for the definition of "life," and one will find a wide variety of definitions. The American Heritage Dictionary of the English Language gives the two following primary definitions: life: 1a The property or quality that distinguishes living organisms from dead organisms and inanimate matter, manifested in functions such as metabolism, growth, reproduction, response to stimuli or adaptation to the environment originating from within the organism. b. The characteristic state or condition of a living organism. After first mentioning that the definition of life is controversial, this is the definition that Wikipedia gives: ". that organisms maintain homeostasis, are composed of cells, undergo metabolism, can grow, adapt to their environment, respond to stimuli, and reproduce." It is also mentioned in Wikipedia that there are some "borderline" cases of life, such as viruses. What is unusual about these "definitions" of life is that none of them define life. They do not define what life is, but rather what life does. Or gives a cyclic argument: life is an organism that carries out life processes. NASA was very concerned about the definition of life. What does extraterrestrial life mean? Is all "life" in the Universe the same as on Earth? Can space travelers recognize life when they see it? They certainly cannot in the original Star Trek series in the episode "The Devil in the Dark," first aired on March 9, 1967. A mining colony on planet Janus VI is being disrupted by an unknown creature. When talking with Chief Engineer Vanderberg, Spock notices a spherical object on his desk. Vanderberg said it was a worthless silicon noduledthat there were thousands of them in the mine. Adjusting their tricorders to silicon life forms, they discover these nodules are life forms. The creature that was destroying the camp and killing the miners was Horta. Horta was the last of his race and was guarding their eggs. Life in the context of this chapter is simply defined as life: a confined set of electrical impulses working in concern to achieve a particular goal. A brain is not required. A jellyfish is one of the more transparent forms of life. Anything more than that is just trimmings.

Physical Chemistry https://doi.org/10.1016/B978-0-12-800513-2.00004-8

755

Copyright © 2018 Elsevier Inc. All rights reserved.

756

4. LIFE SCIENCE

This "electrical impulses" definition of life is in line with science fiction writers who envision the ultimate evolution of mankind to shed its physical container of a body to become a life form of pure energy. And, as they say, today’s science fiction is tomorrow’s science.

4-1.0 Origin of Life Gulliver: "If you were ever to bet it would be a sure thing." Monk: "That’s right." Gulliver: "For instance, if I were to say - hey, let’s play a little poker, you would say - no way. But on the other hand, if I were to say I know where you got your shoes. Now that might give you pause. Now that’s a bet you just might take. You don’t know me. Right? We’ve never seen each other before. There’s no way I know where you got your shoes." Monk: "Exactly." Gulliver: "How much?" Monk: "What?" Gulliver: "I’ll bet you fifty bucks I can tell where you got those shoes." Monk: "The one’s I’m wearing?" Gulliver: "Uh huh." (Monk pulls out a fifty- dollar bill) Monk: "You’re on." Gulliver: "You got those shoes ..... on your feet." Abbreviated conversation from the television series Mr. Monk, Season 6, Episode 9, "Mr. Monk Stays Up All Night".

When and where did we "get" life? Where did life come from is a question that will probably never be answered, mainly because it is a multispeared question. The Ancient Greeks would say life came from the sea. But where did that life come from? There are those who believe life came from elsewheredperhaps Mars. Panspermia (Greek for "all seed") is the hypothesis that life exists everywhere. Life could be on asteroids, meteors, and so forth. It presupposes that life in the form of bacteria can survive space and collisions with celestial objects. There are microbes that exist literally under all conditions on Earth. They survive near sulfur pits. They survive in ice. They survive in boiling water. These bacteria are called extremophiles. They exist under conditions that would kill other organisms (Madigan and Marrs, 1997). Extremophiles may have been present in the early stages of the Earth development. They survive deep-sea vents, geysers, and nuclear waste (http://science.howstuffworks.com/life/cellularmicroscoplic/extremophile.htm). Extremophiles can also teach us about the origin of life because many single-celled extremophiles fall in the category of Archaea. Archaea has DNA that is distinctively different from ordinary bacteria (http://btc.montana.edu/course/aspx/astro. aspx?ext¼4). Knowing that extremophiles exist, and can be the starting point of life forms that followed, they do not provide any clue as to the mechanism by which the first life form came into existence. They do, however, seem to narrow the conditions for the beginning of life to be anywheredhot, cold, mild conditions, extreme conditionsdyou name it. Since the Earth formed 4.5 billion years ago and life came on this Earth 3.5 billion years ago, one may assume that the conditions on Earth were very extreme when life began. In the experimental arena, the first series of experiments to make life in a test tube was by Harold Urey and his student Stanley Miller, or at least molecules associated with life. They made reasonable assumptions about the early conditions on Earth. The conditions were selected to favor chemical

4-2.0 NATURAL SELECTION

757

reactions that synthesized the more complex organic molecules. The experiment used water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2). The chemicals were sealed in a flask that was connected to another flask half-full of liquid water. The source of energy was from a continuous display of electrical sparks to simulate lightening in the early atmosphere. After a day, the solution collected in the trap turned pink in color. After a week, the boiling flask was removed. Paper chromatography of the products revealed the amino acids a-alanine, b-alanine, and glycine. There have, of course, been criticisms of the MillereUrey experiments. One objection was that the products were removed before the application of further electrical discharges, which could have destroyed the products. Perhaps not conclusive in its own right, the MillereUrey experiments also inspired other experiments. It was reported that Joan Oro´ found that hydrogen cyanide (HCN) and ammonia in water yielded large amounts of nucleotide bases (http://www. juliantrubin.com/bigten/miller_urey_experiments.thml). It is one thing to fire up the bricks. It is quite another to build a house with those bricks.

4-2.0 Natural Selection Charles Darwin (1809e82) was going to study medicine, but he found the lectures dull and surgery distressing. He then decided to pursue his interests in natural history. He was introduced to beetle collecting by his cousin William Darwin Fox. Darwin became friends with John Stevens, a botany professor, and other leading naturalists who considered their scientific work as natural theology. Natural theology is a branch of theology, which provides teleological arguments that experiences in nature provide proof for the existence of God. Darwin studied Paley’s Natural Theology or Evidence of the Existence and Attributes of the Deity. Darwin was invited to join the crew of the HMS Beagle with Captain Robert FitzRoy, an English officer of the Royal Navy and a scientist. This was an unpaid position in which he would be a collector of specimens and also a companion to the captain. Robert Darwin, Charles’ father, was at first against him from going on the voyage. But some persuasion by Joshua Wedgewood, his brother-in-law, Robert Darwin agreed to let him go and also to fund his participation. The voyage started on December 27, 1831. Darwin was a geologist, collector of specimens, surveyor and charter of coasts while on the Beagle. He was also a companion FitzRoy, to which they engaged in many discussions related to the Bible. Of great significance is the gift that FitzRoy gave Darwin before the voyage - a copy of Charles Lyell’s Principles of Geology. Over the 5-year voyage, Darwin made many observations, which he wrote down in his notebooks. He collected thousands of plants and animals that he never saw before. He experienced an earthquake in Chile. He saw fossil bones of extinct species next to modern sea shells. And he began to notice variations in the species on the Gala´pagos Islands. He saw birds that ate insects, birds that ate small seeds, birds that crushed large seedsdsome looked like warblers and some looked like woodpeckersdand many other differences between birds in his collection. He met John Herschel in Cape Town, and they discussed how new species replaced extinct species. Darwin took copious amounts of notes of his 5-year voyage. Return now to the collection of birds from the Gala´pagos Islands. When he returned to Great Briton he asked ornithologists what the species of birds that he collected. He was surprised

758

4. LIFE SCIENCE

that he was told they were all finches! He wondered why there were so many different variations of finches in a small area of land. As a believer in the Biblical story of creation while on the Beagle, there was no time for species to evolve. However, Lyell’s Principles of Geology gave Darwin plenty of time for species to evolve. Also influential on Darwin was Thomas Malthus’s An Essay on the Principle of Population. As populations increase there is a struggle for food to survive. The seeds of his theory on the origin of species had been planted. Like a Sherlock Holmes detective story, the evidence was there. All Darwin had to do was to interpret the evidence. He came up with the idea of natural selection. No two members of any species are exactly alike. There are variations among members of species, for if this was not the case then we could not distinguish one person from another. Even a doppelganger is not a precise duplicate of a person. Darwin pointed out that there is a struggle for existence: those that are adapted to change survive. These natural variations give some advantages over others. With a change in the climate, plants that cannot adapt to the change will not survive. This is the whole basis of genetic engineering today. Efforts are being carried out in the laboratory today to genetically modify corn to survive under changing conditions, such as limited rainfall. Darwin spent 20 years, from 1838 to 1858, to examine the data he collected. He would have spent more time on his theory, but Darwin received a paper from Alfred Russel Wallace (1823e1913). In this paper, Wallace described natural selection, the very thing that Darwin was working on for his book. Darwin wrote a letter to Charles Lyell to have Wallace’s paper published in the Proceedings of the Linnean Society as soon as possible. Charles Lyell wrote in the Proceedings in 1859, "So highly did Mr. Darwin appreciate the value of the views therein set forth, that he proposed, in a letter to Sir Charles Lyell, to obtain Mr. Wallace’s consent to allow the essay to be published as soon as possible. Of this step we highly approved, provided Mr. Darwin did not withhold from the public, as he was strongly inclined to do (in favor of Mr. Wallace), the memoir which he had himself written on the same subject, and which, as before stated, one of us perused in 1844, and the contents of which we had both of us been privy to for many years. On representing this to Mr. Darwin, he gave us permission to make use we thought proper of his memoir, &c.; and in adopting our present course, of presenting it to the Linnean Society, we have explained to him that we are not solely considering the relative claims to priority of himself and his friend, but the interests of science generally; for we feel it to be desirable that views founded on a wide deduction from facts, and matured by years of reflection, should constitute at once a goal from which others may start, and that, while the scientific world is waiting for the appearance of Mr. Darwin’s complete work, some of the leading results of his labours, as well as those of his able correspondent, should together be laid before the public." What Lyell wrote is quite revealing, not only about Darwin but about historical science. Darwin knew that he still had work to do but thought the idea of natural selection was so important that he wanted Wallace’s essay to be published immediately. It also clearly establishes the priority to Darwin in reference to 1844. It also shows that considerable thought and reflection went into the interpretation of the huge amount of data that Darwin collected over the years.

4-2.0 NATURAL SELECTION

759

The Origin of Species was published on November 24, 1859. Darwin referred to the 500-plus page work as an Abstract, or an outline of his views. The influence of Malthus is evident in Chapter III, Struggle for Existence. He makes reference to the geometric powers of increase of animals and plants and Nature’s mechanisms of checks and balances to hold reign on these increases. The Great Plague in Europe and the Ebola epidemic in the early 21st century are examples. The influence of Newton, whom Darwin admired, is quite evident in the writing. Just as Newton defined gravity, in Chapter IV, Natural Selection, Darwin defines Natural Selection in terms of what it does rather than what it is: "On the other and, we may feel sure that any variation in the least degree injurious would be rightly destroyed. This preservation of favourable variations and rejection of injurious variations, I call Natural Selection." Newton’s influence is also present in Chapter V, Laws of Variation, in which Darwin wrote: "I have hitherto sometimes spoken as if the variations - so common and multiform in organic beings under domestication, and in a lesser degree in those in a state of nature - had been due to chance. This of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation." The structure of this sentence is similar to that of Newton in regard to having no hypothesis for the cause of gravity. It also underscores what opponents of Darwin’s theory seem to ignore: variations to Darwin are not chance events. A clear reference to Newton is made by Darwin in the last paragraph of The Origin of Species: "Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved." Darwin had an ambition to become a clergyman and studied Anglican theology at the University of Cambridge. As a man of religious views, on the voyage of the Beagle, he looked for the center of creation to explain the distribution of species that he observed. On this voyage, he became skeptical about the Bible as history and wondered why all religions were not equally valid. He knew of Paley’s argument for design but felt that natural selection with adaptation removed the necessity of design. When he wrote The Origin of Species, Darwin believed in God as a "first cause" (as evidenced by the last paragraph in his book) and described himself as a theist. After his marriage to Emma in 1939, he engaged in many discussions with her about Christianity for many years. Emma was a Unitarian. While on the Beagle, he wondered why animals suffered, one species being the food of another. This suffering came home to him when his daughter, Anne, died at the age of 10 in 1851. In later life, Darwin admitted that "agnostic" would be a good description of his state of mind. There are many different representations of the "Tree of Life." One representation that reflects Darwin’s view of ". simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved" is shown in Figure 4-2.1. This image has the three major

760

4. LIFE SCIENCE

Bacteria

Archaea

Eukaryota

Green Filamentous bacteria

Fungi Halophiles

Spirochetes

Proteobacteria

Gram positives

Animals Plants

Methanosarcina Slime molds

Ciliates

Methanobacterium Entamoebae Flagellates Methanococcus

Cyanobacteria Planctomyces Bacteroides Cytophaga

T. celer

Thermoproteus

Trichomonades Microsporidia Diplomonads

Pyrodicticum

Thermotoga Aquifex

LUCA FIGURE 4-2.1 Phylogenetic tree of life. The phylogenetic tree (evolutionary tree) is speculatively rooted tree based on rRNA genes. The three life domains (bacteria, archaea, and eukaryota) are rooted to the LUCAdLast Universal Common Ancestor. Source: Wikipedia Public Domain.

branches of life stemming from one source. The bacteria branch represents prokaryotesdcells with no cell nucleus or organelles in its cytoplasm except ribosomes. At the other extreme, the eukaryota branch is characterized by specialized organelles in the cytoplasm and a cell nucleus that encloses the genetic material into chromosomes. The archaea branch is in between the bacteria and eukaryota branches. It is similar to the bacteria branch except that the archaea branch has more complex RNA polymerases.

4-3.0 Genetics Gregor Mendel (1822e84) was a scientist and a friar. Crossbreeding of plants and animals was known for centuries. The breeders knew what worked but did not perform any systematic study of the process. During the period 1856e63, Mendel worked on the crossbreeding of pea plants. He systematically followed and recorded the plant height, the shape and color of the pods, the shape and color of the seeds, and the position and color of the flower. A yellow pea crossbred with a green pea always resulted in a yellow pea. But when these first-generation peas were crossbred the green pea appeared in one out of four second-generation peas. Similar results were observed for the other traits. Mendel coined the terms "recessive" and "dominant" for these traits. Crossbreeding had now become mathematical. Crossbreeding can be represented in a similar way as two coins that can be either heads (H) or tails (T). The equation for crossbreeding begins with one purely regressive state (r, r) and one purely dominant state (d, d). The result is

4-4.0 DIVERSITY OF LIFE AND ENVIRONMENTAL PRESSURE: NATURAL SELECTION AT WORK

761

two hybrid states, (r, d) and (d, r), each having the dominant characteristic. Using these hybrids the outcomes can be generated by an equation, ðrþ dÞ2 ¼ rr þ rd þ dr þ dd ¼ ðr; rÞ þ ðr; dÞ þ ðd; rÞ þ ðd; dÞ

[4-3.1]

where the rightmost expression is to be consistent with the introductory notation. There are three configurations that contain at least one dominant characteristic, and only one in which the recessive state is expressed (rr). Reproduction now had a mathematical foundation. It was later discovered that the basic unit of these characteristic traits is the genes. A collection of genes is called a chromosome, a welldefined structure of genetic material.

4-4.0 Diversity of Life and Environmental Pressure: Natural Selection at Work Life responds to the pressure of the immediate environment. The response is not immediate but takes place over many generations. Natural selection takes place as follows. Let there be a population of moths of which half are white in color and the other half are brown. According to Mendel’s genetics law, the first round offspring will be one-fourth white, one-fourth brown, and one-half tan. Place these moths in two different environments: a forest with trees and a background of snow on the mountain. Because of the camouflage effect, the white moths have a better chance of survival with the snow background, and the brown moths have a better chance of survival in the dark forests. In each case, the genetics dictates that brown and tan moths will be present in the snowy region, but because of their visibility they are juicy morsels for the resident predators. Likewise the white moths will be present in the forest domain, but in reduced numbers for the same reason. What if the climate were to change, where the snow on the mountains melts? Now the white moths are "made visible" and thus become an item on the menu. In contrast, the brown moths become more "invisible" and their numbers multiply. The process of Natural Selection presupposes that the genetics provides a small population of "mutations" that are already predisposed to a resulting change in the local environment. This is what is meant by environmental pressure. Once the species has adapted to the local environment, it becomes the species habitatdthe natural home of the animal or plant. This is why Darwin’s finches are variations of the same species. This is also why there is a diversity of life. Polar bears and penguins live in the coldest regions of Earth, literally poles apart. Polar bears live in the northernmost region of the Earth, within the Arctic Circle where temperatures can likewise be as low as 50 degrees Fahrenheit but generally fall in a range of temperature 40 to þ32 degrees Fahrenheit. Penguins live at the bottom of the Earth, on the continent of Antarctica where 50 degrees Fahrenheit has been described as a "balmy" day.

4-4.1 Polar Bears On February 19, 2006, the news program 60 Minutes first aired a segment titled "Global Warming." Scott Pelley began a report on the polar bear with the words: "The name ‘Arctic’ comes from the ancient Greek meaning ‘land of the great bear.’"

762

4. LIFE SCIENCE

The "great bear" can weigh as much as 1600 pounds, and the head-to-tail length can exceed 8 feet. The polar bear evolved to survive in the frigid conditions of the Arctic. Under the camouflage of heavy white fur is a black skin that absorbs the Sun’s rays to provide warmth. The diet of the polar bear consists mainly of seals. Since seals feed on fish under the sea ice, the seal must make breathing holes in the ice. The polar bear has evolved to take advantage of that fact. With its excellent sense of smell, the polar bear can find breathing holes of seals because they exhale when they come up for air. Because sea ice is relatively thin, the weight of the polar bear must be distributed over a large area of the ice to reduce the pressure, defined as weight/area. The polar bear paws have a large surface area and are very flat so that the pressure of the weight of the polar bear is spread out over a large area. While not complimentary to humans, to have large flat feet is so the polar bear does not break through the sea ice. The polar bear crouches near the hole until the seal appears. The long neck and muzzle of the polar bear is well suited to reach deep into these holes to catch the seals. This method of hunting is called still-hunting. Polar bears are excellent swimmers, sometimes swimming as far as 100 miles in search of sea ice. Figure 4-4.1 shows a photo of a polar bear showing his long neck and a mold of his large paw. The width of the paw indicated by the red double arrow is 11 inches.

FIGURE 4-4.1 Polar bear at the Kansas City Zoo. The name of the bear is Berlin. The long neck of the polar bear evolved for hunting seals as they came up for air in their breathing hole in the sea ice. The width of the paw as indicated by the red line is 11 inches. The large paw is to distribute the bear’s weight on the sea ice so as to not break the ice.

Because of global warming, the sea ice is receding at a rate faster than ever recorded in history. In fact, the much sought-after Northwest Passage connecting the northern Atlantic and Pacific Oceans over the centuries became a reality in 2006, as apparent in satellite images, showing the location of sea ice. With the disappearance of sea ice is the disappearance of still-hunting and the appearance of the real possibility that polar bears will become extinct.

763

4-4.0 DIVERSITY OF LIFE AND ENVIRONMENTAL PRESSURE: NATURAL SELECTION AT WORK

The topic of the cover of the April 3, 2006, issue of TIME magazine has the words: "SPECIAL REPORT GLOBAL WARMING." To the left is the warning: BE WORRIED. BE VERY WORRIED" and to the right is a photograph of a polar bear on a floating section of thin ice. Inside this issue an expanded form of this photograph begins the article, and the caption for the photograph reads: "AT SEA In the Canadian high Arctic, a polar bear negotiates what was once solid ice. Bears are drowning as warmer waters widen the distance from floe to floe." In his report of polar bears on CBS 60 Minutes, Scott Pelley went with Canadian scientist Nick Lunn to Wapusk National Park, located above the subarctic region of Hudson Bay. Lunn was making an annual report on polar bears, which in this region the bear population was supposed to be the healthiest in the world. Now the ice is breaking up three weeks earlier than 30 years ago. At this trip the female bears weighed considerably less than the trip before. Lunn said that the population of polar bears in the mid-1980s and 90s was approximately 1200 animals. At last check the population declined to below 1000. The situation has not gotten better for the polar bear in the following 12 years. Kendra PierreLouis reported in The New York Times that the lack of sea ice still presents a problem for survival (Pierre-Louis, 2018). The news report was about the work being done by Anthony Pagano, which was recently published in the journal Science. Video cameras were affixed to GPS-equipped collars on nine female polar bears. Eleven days later the scientists retrieved the cameras. The results are obvious. Four bears gained weight because they caught seals. Four bears lost weight because they did not catch seals. The problem remains. With less sea ice, there is less food and the polar bear has to travel much further to find sea ice. We return to the election year of 2008. With all of the focus on polar bears at that time, such as the cover on Time magazine and the 60 Minutes special, it is not unreasonable that there were many who have engaged in dialogues about the polar bear. The issue has turned political. Here is one Letter to the Editor to the Kansas City Star on February 11, 2008, which points out polar bears don’t vote: "The Kansas City Star February 11, 2008 Polar bears vs. people I read on the front page (2/4) that Kansas City’s congressional representative, Emanuel Cleaver, puts the concerns of polar bears above the concerns of his constituents. The people in his districtdthe same people who voted for himdare paying high gasoline prices and need a domestic source of fuel in order to see prices at the pump reduced, not to mention the national security concerns related to foreign oil. But Cleaver appears to be favoring the bears. If Cleaver is so concerned about global warming, why is he jetting around the world visiting 13 far-away locations (mentioned in the article) to watch ice melt? Doesn’t he realize his carbon footprint is adding to the much-ballyhooed warming he is so worried about? I would suggest he remain in Washington, consider all sides of the issue, not just the liberal side that pushes the warming scam, and vote for more oil exploration to help his constituents. Aren’t the voters in his district the ones he should be worrying about? Bears don’t vote. Dave King Leawood"

764

4. LIFE SCIENCE

It is true that bears don’t vote, but voting for more oil exploration does not help Cleaver’s constituents either because his constituents in Missouri don’t drill for oil. There was a response to the King Letter: "The Kansas City Star February 16, 2008 Kudos for Cleaver Unlike Dave King (2/11, Letters, "Polar bears vs. people"), I was pleased to see Congressman Emanuel Cleaver take a forward-looking stance on climate change. He is a thoughtful leader who is willing to take a tough position today in order to positively influence tomorrow’s world. According to the Intergovernmental Panel on Climate Change, warming of the climate is undeniable. The amount of temperature and sea level rise in the next century will vary greatly depending on the fossil intensity of human activity. Polar bears are the ’canary in the coal mine.’ Stay tuned for the next victim in this unfolding saga. Low gas prices have only fueled American love of large, inefficient vehicles and encouraged urban sprawl. Recent price increases have forced us to look for more fuel-efficient methods of transportation. Drilling in Alaska will not solve the problem of America’s unhealthy dependence on fossil fuels. Please write to commend Cleaver for taking a responsible position on this issue. Carol Petrini Independence"

One article in The Kansas City Star pointed out that there was government protection for the polar bear: "The Kansas City Star May 15, 2008 Polar bear gets new protection By H. JOSEF HERBERT, Associated Press Writer Put at risk by global warming, the polar bear is getting a life line: The government has declared it a threatened species in need of increased protection. But another round of legal battles surrounding the majestic animal may be just beginning. The Interior Department put the bear under the protective umbrella of the Endangered Species Act on Wednesday, concluding what biologists have been saying for years - the bear is on the way to extinction because of the rapid disappearance of the Arctic sea ice upon which it depends. Scientists predict sea ice melting will continue and even accelerate because of global warming. ‘This in my judgment makes the polar bear a threatened species, one likely to become in danger of extinction in the foreseeable future,’ said Interior Secretary Dirk Kempthorne, punctuating his point with an array of slides, charts and maps showing the changing ice flows of the Arctic. ..........................." But a Letter to the Editor which followed up this article noted that this "protective umbrella" was government propaganda: "The Kansas City Star May 24, 2008 Weak protection for polar bears

4-4.0 DIVERSITY OF LIFE AND ENVIRONMENTAL PRESSURE: NATURAL SELECTION AT WORK

765

Finally, after several years of lawsuits and thousands of letters, the Bush administration has listed the polar bear under the Endangered Species Act (5/15, A-1, ‘Polar bear’s new status draws growls’). Aren’t we all glad? Not so fast: There is a clause in the act that excludes global warming from the list of threats the federal government must consider when trying to protect polar bear habitat. Instead of ‘endangered,’ the polar bear is listed as ‘threatened’ and gets more limited protection than that provided by a global warming listing. Of course, global warming is the dire threat facing polar bears today, so this means nothing. During the months leading up to this weak decision, oil leases were issued by the Bush administration in prime polar bear habitat. So what else is new? Bette Grotegut Plattsburg, Mo."

Bjorn Lomborg, an economist who bills himself as The Skeptical Environmentalist (title of his 1998 book), waded in the polar bear issue in his 2007 book Cool It. As to the stabilization of the polar bear population, Lomborg pointed out that more polar bears are lost each year by the hand of hunters compared to about 15 due to greenhouse gases. He suggested that if we really want to stabilize the polar bear population, one should first curb the hunting of polar bears before imposing restrictions on greenhouse gases, which would harm the economy. However, stabilizing the polar bear population is not the underlying reason for the movement "save the polar bear." The underlying reason environmentalists, scientists, and concerned citizens want to "save the polar bear" is to actually save the habitat of the polar bear (along with the Inuit Indians). The alarm is the rapid melting of the sea ice. Saving the habitat of the polar bear also saves our habitat, which is also subject to the effects of global warming. Since, by definition, there is no land under the sea ice in the Arctic, the melting of sea ice does not affect the ocean level. The importance of sea ice is that it reflects more sunlight than water. Melting the sea ice means more energy is absorbed by the Arctic Ocean, raising the temperature of the water. What is the effect of warmer water flowing out of the Arctic Ocean? Warmer water will reach Greenland, and the glaciers of Greenland will begin to melt. So what if Greenland glaciers melt? The land under the glaciers, once exposed, will absorb more sunlight with an increase in global temperature. If all of the glacier ice melts in Greenland, the sea level will rise worldwide about 15 feet. Should that occur, much of Florida, including coastal golf courses, will be under sea. Clearly the habitat of the Miamians would be changed! The website of the Center for Biological Diversity (biologicaldiversity.org) has the heading (in 2016) "Saving the Polar Bear." Their concern is not only with the polar bear but all species that are on the verge of extinction due to human activity.

4-4.2 Penguins At one time, Antarctica was part of the supercontinent Pangea and had a tropical climate that covered the land with forests and various ancient forms of life (see Chapter 3). About 175 million years ago, Pangea broke apart into minor supercontinents, one of which was Gondwana, which in turn broke apart to form South America, India, Africa, Australia, and Antarctica. Approximately 25 million years ago, Antarctica began to acquire its most characteristic traitdice. It should be obvious that food sources in the tropics are different than potential food sources on ice-covered land with temperatures well below freezing and high winds of Antarctica. It is first

766

4. LIFE SCIENCE

noted that the penguin is a bird. The penguin is an example of evolutionary adaptation for survival over the transition period of the continent of Antarctica. There are three modes of transportation for any species: fly through the air, walk on the land, and swim through the waters. The trade-off in the evolutionary pathway for penguins was to give up flying in favor of swimming as a means of finding food. The wings became flippers, the light bones became heavier bones, the body shape became more streamlined for swimming underwater, and the body size and ability to hold their breath longer allowed the penguin to dive deeper for food. Penguins evolved not only for the cold climate but also the warm climate. The warm-climate penguin species include Snares, Yellow-eyed, Humboldt, Fiordland, Erect-crested, African, and Magellanic. The cold-climate penguin species include Southern rockhopper, Northern rockhopper, Chinstrap, Royal, Adeline, Gentoo, King, Emperor, and Macaroni. Photos of Gentoo, King, and Humbolt penguins at the Kansas City Zoo are shown in Figure 4-4.2.

A

C

B

E

D

FIGURE 4-4.2 Penguins at the Kansas City Zoo. A: Gentoo penguin. B: King penguins. C: Humbolt penguins. D and E: Penguins "flying" through the water.

For the last 38,000 years the diet of both the Emperor and Ade´lie penguins was once primarily fish as determined by fossil eggshells. Approximately 200 years ago the diet of Ade´lie penguins went from fish based to krill based. This is apparently due to the hunting of the Arctic Fur Seals and Baleen whales, the chief competitors for krill. Krill are shrimp-like animals that feed off of sea algae that grow on the underside of sea ice.

4-4.0 DIVERSITY OF LIFE AND ENVIRONMENTAL PRESSURE: NATURAL SELECTION AT WORK

767

The Emperor penguin became a movie celebrity with the 2005 motion picture March of the Penguins. The Emperor penguin is the tallest (reaching 122 cm or 4 feet in height) and heaviest (22e45 kg or 49e99 pounds) of the penguins. Their food consists mainly of fish but includes crustaceans, such as krill, and cephalopods, such as squid. The subject of the movie was the annual migration of the Emperor penguin to breed their young. They march, virtually in single file, from the shallower regions of the ice to thicker ice for the breeding grounds, a trip that is from 30 to 70 miles. The female lays one egg, which is incubated by the male while the female returns to the sea to feed. The male and female take turns caring for their chick in the colony and foraging for food, perhaps up to 900 miles, to feed the chicks. The rising global temperatures are threatening the Emperor penguins on two fronts. The melting of sea ice threatens the food supply of krill, which thrive under the sea ice. The melting of land ice forms deep crevices, which may block the migration to the breeding grounds and into which penguins may fall to their death.

4-4.3 Bees There is also a movement to "save the bees." This is one case where the movement is to actually save the bees. Why save the bees? Their share of worldwide pollination is about 80%. Of the top 100 crops used for food, about 70 are pollinated by bees. Fruits, nuts, and vegetables are on the list. Bees also pollinate wildflowers that make our fields look beautiful. Pollination of flowers by bees gives us different varieties of honey. A commercial beehive at High Point Honey located in Independence, Missouri, is shown in Figure 4-4.3 along with a field of clover, two samples of honey

B

A

C

FIGURE 4-4.3 Busy as a bee. A: Bee hive at High Point Honey located in Independence, Missouri. B: A field of cloverda haven for bees. C: Honeydleft to right: wildflower honey, clover honey, honeycomb that was in a jar of honey.

768

4. LIFE SCIENCE

(clover and wildflower), and a honeycomb that came with a jar of honey. Honey is the product of flower nectar and the digestive tract of bees. Honey has been used as a natural remedy for thousands of years. It is a natural sweetener. Honey has many medicinal uses, such as direct application on cuts and burns because of its antimicrobial nature. All of human ingenuity and scientific knowledge have not been able to do what the bee and flowers have been able to dodproduce honey. And unlike the bee, if human industry could synthesize honey for medicinal purposes, this "miracle drug" would probably cost too much for most of the people to afford. Even though the honey bee plays an important role in our food supply, we are nonetheless systematically killing the bees. Scientists know that there are a variety of reasons why bees are dying; and also that these reasons are interconnected. We spray our plants with pesticides that we ourselves would not eat or breathe, yet that is what we are feeding the bees. Biologists have identified more than 150 chemical residues in bee pollen (http://www.greenpeace.org/ usa/sustainable-agriculture/save-the-bees). We pollute the air so much that you can see people wearing masksdbees don’t have masks to wear. We destroy their habitats, not only by chemical sprays but also by physically destroying the land. Ecological farming will not only save the bees. It may save us as well.

4-4.4 Bats Bats are specially evolved mammals. Their forelimbs have been adapted into skin-covered wings for flight. They are the only mammals that are capable of sustained flight. They have reached ground speeds up to 99 miles per hour. Bats are more maneuverable than birds, which is an advantage to insectivorous bats. Most of the rest of the bats are frugivores, the fruit-eating bats. Most bats are nocturnal and live in caves and use sonar to maneuver during their flights. As with Darwin’s finches, bats have evolved different physical characteristic based on their diet. Bats that eat insects have as many as 32 small teeth, whereas vampire bats have only 20 teeth with upper incisors that are razor sharp. The bats that feed on soft-bodied insects have more but smaller teeth than those that feed on hard-bodied insects. Fruit bats have teeth adapted for crushing. On the April 5, 2009, CBS Morning News, one of the stories was that bats were coming out of hibernation early, and that bats were dying for no apparent reason. Why should this be important? As fearful as some might be of bats because of movies such as Dracula, the bats perform a service to humans by eating insects. The disappearance of bats begins a chain reaction. If there are more insects because there are fewer bats, the first thing that comes off the shelf are the pesticides. More pesticide usage means a higher cost of farming. The farmer, as would any businessman, passes off the higher cost of farming to the consumer: the higher cost of food. But the higher costs are not limited to food when more pesticides are used.

4-4.5 All Life Affects the Ecosphere In accordance with Natural Selection, all life has evolved to be able to exist in its local habitat. Life has, in fact, become part of the habitat. Prairie grasses in the Great Plains survive the harsh winters, high winds, and drought because they are perennial plants with long roots with an extended root system. The American bison is adapted to the Great Plains by the ability to grow a heavy coat during the winter season and primarily eats prairie grass, the adopted plant

4-5.0 LIFE IS ONE BIG SMORGASBORD

769

of the Great Plains. The great herds of the American bison could not survive in a mountainous habitat as does the wolf. Even though there was plenty of flat space for herds, the American bison could not survive in a desert environment. What this means is that the local surroundings is the habitat of the plants and animals, and combined they become the local Ecosphere. What happens when an outside species enters the habitat? If there is no predator, then the invading species may simply take over. Assume that the invading species in this scenario is a prickly plant that has evolved long sharp spines for protection. In other words, a form of cactus that can survive the prairie environment. If the invading plant wins over the prairie grass, the buffalo will starve and eventually die out. The prickly plant has changed the local Ecosphere because it has changed one part of the Ecosystem that was defined as a habitat for the American buffalo.

4-5.0 Life Is One Big Smorgasbord There is, literally, only one thing that all life does. And that is to perpetuate life. Life has only two roles in the perpetuation of life: to eat and to be eaten. For life to exist on Earth, there must be an external source of energydthe Sun. The only living organisms on Earth that can tap into that energy are plants that are capable of photosynthesis. Not all animals eat plants. What this means is that carnivores must eat animals that eat plants to get the necessary "sunlight" energy. This sets up the concept of a "food chain" in the passage of sunshine captured by plants to other life forms. In the episode "Ocean Life" of the television series Bill Nye the Science Guy, the food chain was illustrated as a linear progression of plants and/or small animals being eaten by larger animals. The food chain envisioned is linear with plants at the bottom and usually humans at the top. This image is shown in Figure 4-5.1 using Pac-Man characters.

FIGURE 4-5.1 Pac-Man representation of the food chain. The concept of a food chain is that smaller animals are eaten by larger animals.

The metaphor of a food chain does not reflect reality. The very small can be eaten directly by the very large without the intermediate steps of a food chain. Plankton is a microscopically small animal that floats in the sea. A gray whale reaches 49 feet in length and weighs about 40 short tons. Gray whales have been seen skimming the ocean surface with their mouths open, feeding on the plankton.

770

4. LIFE SCIENCE

To reflect the real situation, the food chain is replaced by a foods-ball, a spherical structure that emerges when the food sources are connected to all of the food recipients. The role of humans in the foods-ball is not only that of the "eater" but also the "be eaten" in the foods-ball scheme. This does not mean that humans are part of a steady diet, nor does it mean the human is fully consumed. A mosquito feeds on human blood in a manner similar to humans feeding on cows by taking their milk for human consumption. Scavengers, bugs, and worms feed on the human carcass. The foods-ball is a three-dimensional object, which is represented in Figure 4-5.2 as a

humans large birds large animals small birds large fish small animals small fish

insects

plants FIGURE 4-5.2 The foods-ball. Nature shows no preference when it comes to perpetuation of life forms. The black arrows connect living organisms that are part of the diet of other living organisms. The arrows point in the direction of eaten to eater. The red arrows are a reminder that humans are also on the menu of some insects and animals.

two-dimensional projection. The arrows point in the direction of eaten to the eater. The red arrows are reminders that the human species is also on the menu of other members of the foods-ball.

4-6.0 Life is Like a Box of Chocolates "Mama always said life was like a box of chocolates. You never know what you are going to get." Forrest Gump, in the 1994 movie Forrest Gump.

4-6.0 LIFE IS LIKE A BOX OF CHOCOLATES

771

Shown in Figure 4-6.1 are images of many activities that take place in the eukaryote cell. The total image looks like a box of chocolates. There are some chocolates with nuts. Some with caramel. Some are cream filled. The caption identifies the activities.

FIGURE 4-6.1 General view of cell growth. a) Nondividing cells with chromatin network and deeply stained nucleoli. b) Nuclei preparing for division. c) Dividing cells showing mitotic figures. e) Pair of daughter cells shortly after division. Source: Wikipedia Public Domain.

How does one go about making a box of chocolates? First, one has to organize a factory that is to produce the box of chocolates. The factory itself can be a large room with an inner office for the director. On the main floor is all of the necessary equipment to produce a box of chocolates. The foreman is the person who communicates instructions from the director to the workers, and vice versa. The foreman conveys the director’s orders to the leader of each group. Each group leader passes the information on to the workers. The workers form an assembly line. The electrical machinery is run by a generator in the room. All of the necessary material is distributed about the factory room. To manufacture the chocolates, the first thing one must have is a recipe. Since the competition is strong in the chocolate business, the recipe is written in code. From that recipe, one learns what ingredients are needed, the amount of each ingredient, the order of mixing the ingredients, the preparation for cooking the mixture, what goes on the inside of the chocolate candy, the distribution of the chocolates in the box, and finally the packaging of the box of chocolate candy.

772

4. LIFE SCIENCE

Life is like a box of chocolates. The factory is the eukaryotic cell, shown in Figure 4-6.2. The inner room (1 and 2 in the figure) is where one can find the director. The other items represent the machinery. The power to run the machinery in the factory corresponds to the mitochondrion in the cell, item 9 in Figure 4-6.2, and shown in Figure 4-6.3. The mitochondrion is responsible for the energy production in the cell and to regular cell metabolism.

FIGURE 4-6.2 Animal cell. 1) Nucleolus; 2) Nucleus; 3) Ribosomes (dots on rough reticulum walls); 4) Vesicle; 5) Rough endoplasmic reticulum; 6) Golgi apparatus (or Golgi body); 7) Cytoskeleton; 8) Smooth endoplasmic reticulum; 9) Mitochondrion; 10) Vacuole; 11) Cytosol; 12) Lysosome; 13) Centriole; 14) Cell membrane. Source: Wikipedia Creative Commons.

50 nm

FIGURE 4-6.3 Mitochondriadmammalian lung. Transmission electron microscopic image of a section cut through mammalian lung tissue, showing the mitochondria. Source: Wikipedia Public Domain.

773

4-6.0 LIFE IS LIKE A BOX OF CHOCOLATES

There are 20 ingredients that go into the making of the chocolate. These are the amino acids: alanine (ala), arginine (arg), asparagine (asn), aspartic acid (asp), cysteine (cys), glutamine (gln), glutamic acid (glu), glycine (gly), histidine (his), isoleucine (ile), leucine (leu), lysine (lys), methionine (met), phenylalanine (phe), proline (pro), serine (ser), threonine (thr), tryptophan (trp), tyrosine (tyr), and valine (val). The code for an ingredient is represented by four basesdtwo purine bases, which are identified as having two ring structures, and two pyrimidine bases, which are identified and having only one ring structure. The purine bases are adenine (A) and guanine (G); the pyrimidine bases are thymine (T) and cytosine (C). When the bases are attached to a sugar, the unit is called a nucleotide. The structures of the four nucleotides are given in Table 4-6.1.

TABLE 4-6.1 The Nucleotide Structures Purine Bases Adenosine

Guanosine

Pyrimidine Bases Cytidine

Thymidine

As a takeoff of the old "screwing in a light bulb" jokes: How many bases does it take to code for the amino acids? Answerdthree. Consider the possible combinations: for one base, there are four possibilities; for two bases, there are 4  4 ¼ 16 possibilities; and for three bases, there are 4  4  4 ¼ 64 possibilities. One need not go further. With three bases there are more than enough possibilities to code for the 20 amino acids. In fact, there are too many. But what law is there that says the mathematics must give the exact number? There is room for degeneracy. The set of three bases is called a codon. As with any written sentence, there must be a signal to start and a signal to stop. Except for the 1927 story "Archie and Mehitabel" by Don Marquis, the beginning of a sentence is indicated by a capital letter (C). The end of a sentence is indicated by a period (.). Likewise, there is a "start" and a "stop" code to tell where the recipe starts and ends. The codes for each specific amino acid are given in Table 4-6.2. The nucleotides are fixed together in a linear string that becomes the coded message for life: the genetic code. The genetic code is the recipe for chocolates in the factory analogy.

774

4. LIFE SCIENCE

TABLE 4-6.2 Codons First Position 50 end

U

C

A

G

Third Position 30 end

Second Position U

G

A

C

Phe

Ser

Tyr

ys

U

Phe

Ser

Tyr

Cys

C

Leu

Ser

STOP

STOP

A

Leu

Ser

STOP

Trp

G

Leu

Pro

His

Arg

U

Leu

Pro

His

Arg

C

Leu

Pro

Gln

Arg

A

Leu

Pro

Gln

Arg

G

Ile

Thr

Asn

Ser

U

Ile

Thr

Asn

Ser

C

Ile

Thr

Lys

Arg

A

Met

Thr

Lys

Arg

G

Val

Ala

Asp

Gly

U

Val

Ala

Asp

Gly

C

Val

Ala

Glu

Gly

A

Val

Ala

Glu

Gly

G

The activities in the chocolate factory have analogies in the inner workings of the cell. The actions that take place in the cell are shown in Figure 4-6.4. Shown at the top of the image is the recipe represented as the double-stranded DNA. From this code is constructed a "mirror image" molecule, the RNA molecule that "transcribes" the message. The transcription involves the recording of the recipe in terms of the complementary base. The complementary base pairs are A with T and G with C. Transcription is the same as "mirror writing" as used by Leonardo da Vinci for his private notes. The message is revealed when placed in front of a mirror. The "mirror" in this case is the messenger RNA, or mRNA, in which the message is generated with complementary base pairs as well. In this analogy, the messenger RNA is the foreman who leaves the cell nucleus (inner office) to go to the cytoplasm (factory work space). The message carried by the foreman is given to the ribosomes (the group leaders of the factory). The group leaders call on the appropriate workers, the transfer RNA (tRNA), to bring the appropriate amino acid (material) to be assembled in assembly line fashion. Figure 4-6.5 shows the assembly line of the factory. Each ingredient is added by the factory worker to the growing product by having the appropriate worker attach the correct ingredient. In this figure the factory worker is transfer RNA, denoted by "TRNA" (the usual notation is tRNA), with the complementary codon sequence, and the correct ingredient is the amino acid. The process continues until the "stop" button of the code is reached.

4-6.0 LIFE IS LIKE A BOX OF CHOCOLATES

775

FIGURE 4-6.4 Synthesis of protein. The master plan written in the base sequence of the DNA is transcribed to RNA, which is then written in messenger RNA language. This information is then passed into the main assembly room of the cell. The group leader ribosome then directs the worker tRNA to link their amino acid to the growing protein chain. Source: Wikipedia Public Domain.

FIGURE 4-6.5 The assembly lineup. The messenger RNA provides the template upon which the tRNA recognizes. The incoming tRNA is carrying an amino acid that matches the template. The ribosome directs the attachment of the amino acid to the growing peptide chain. Source: Wikipedia Creative Commons.

776

4. LIFE SCIENCE

4-7.0 The Packaging of the Genetic Information The structure of deoxyribonucleic acid is a double helix stabilized by hydrogen bonding by complementary purineepyrimidine base pairs: A-T and G-C. There are approximately 10.5 base pairs per turn of the helix when in the dominant B-form. There are other forms of DNA based on the spacing between adjacent base pairs, such as A-DNA, C-DNA, and Z-DNA. There is a major groove and a minor groove in which linear molecules such as proteins might bind. Planar molecules might be able to squeeze between the base pairs. The structure of DNA is shown in Figure 4-7.1.

FIGURE 4-7.1 DNA double helical structure. The double helix structure of DNA is stabilized through hydrogen bonding between complementary purine and pyrimidine base pairs as indicated in the figure: 2 hydrogen bonds for the A-T pair and 3 hydrogen bonds of the G-C pair. The sugar-phosphate backbone exhibits a major and a minor groove in the helical turns, with the phosphate groups on the outside. Source: Wikipedia Creative Commons.

The specific arrangement of base pairs along the DNA molecule is the genetic information for that particular organism. In humans the length of DNA that contains this information is about 2 m, or a little over 6 feet. How can a length that is the height of a human fit in a cell that is 2 nm in diameter, or about 109 its size? This is a particularly fascinating enigma when the stiffness of DNA is taken into consideration. This problem is like trying to package a string 16,000 miles long (65% of the radius of the Earth) into a box that is one inch in length.

4-7.1 DNA: First-Order Folding The dates are June 28eJuly 2 in 1982. It is the Gordon Research Conference on "Nuclear Proteins, Chromatin Structure and Gene Regulation" held at a private school in Tilton, New Hampshire. The Chair for this conference is Kensal E. Van Holde from the Department of Biophysics at

4-7.0 THE PACKAGING OF THE GENETIC INFORMATION

777

Oregon State University. The conference is well attended. Perhaps better described as over subscribed. Chromatin structure and function is actually two areas, each with many researchers. Talks on both topics were presented. The usual format of a Gordon Conference is to give each invited speaker about an hour, to leave time for questions. The talks are given in the morning and evening, with the afternoons free. At this particular 1982 Gordon Conference, each speaker was given 20 minutes with no time for questions, and the evening sessions lasted late into the eveningdapproaching midnight. The subject of chromatin structure and function had been a "hot topic" for more than 10 years. Let us go back an additional 10 years, to the early 1970s, and recollect an event that took place in the office of J. M. Schurr in the Department of Chemistry at the University of Washington in Seattle, Washington. Barbara Shaw, a former doctoral student of Schurr and, at that time, a postdoctoral colleague of Van Holde, was telling him of a model that they proposed for the first-order folding of DNA. The model consisted of a complex of two each of the histones H2A, H2B, H3, and H4 with about 150 base pairs of DNA wrapped around the exterior of the histone complex. This was a novel concept because the usual picture of a DNAeprotein complex was that the arms of the protein hugged the DNAdthe protein was on the outside of the complex. And there was the problem of ˚ ), the stiffness of the DNA. The persistence of the DNA is on the order of 150 base pairs (about 525 A ˚. so it would require a large amount of energy to bend the DNA into a loop of diameter 110 A We now move forward in time from that meeting to 1974. With knowledge of how the histones self-aggregate in solution, Ken Van Holde with collaborators C. G. I. Sahasrabuddhe and Barbara Ramsay-Shaw were the first to propose a detailed model of DNA packaging in which the DNA folded about a core of aggregated histone molecules. The paper appeared in Nucleic Acids Research (Van Holde et al., 1974). The abstract of their paper read: "A model is proposed for the structure of nuclease-resistant chromatin particles. The model is novel in that it proposes that the DNA in such a particle is wound around a protein core made up of the hydrophobic regions on the histone molecule." Van Holde et al. (1974).

Through hydrophobic interactions, two each of the histones H2A, H2B, H3, and H4 spontaneously aggregate. Flopping on the surface of this eight-membered complex are positively charged strands of molecule that interact with DNA through its major and minor grooves. But Nucleic Acids Research was not the first choice for publication. Van Holde sent the paper first to the journal Science. And that is where behind-the-scene politics came into play. About 6 months after submission of the Van Holde, Sahasrabuddhe, and Ramsay-Shaw paper to Science with no word, an inquiry was made as to the status of the paper. The response was that Roger Kornberg already published a paper on the subunit structure of chromatin. Van Holde then sent the "Core Particle Paper" to Nucleic Acids Research. Roger Kornberg, son of Nobel Laureate Arthur Kornberg, published a paper in Science in which he proposed a 200 base pair repeat unit (Kornberg, 1974). The Kornberg paper had no details at all about the structure of the 200 base pair repeat unit. Around this time, Don and Ada Olins were also working on the structure of chromatin and came up with a repeat unit model (Olins and Olins, 1974). They referred to this repeat unit as a "n body" and were pushing for their nomenclature. The nomenclature eventually adopted was that the repeat unit of chromatin be called a nucleosome. The nucleosome consisted of approximately 200 base pairs of DNA wrapped around the complex of two each of the histones H2A, H2B, H3, and H4. There is a fifth histone, H1, that holds

778

4. LIFE SCIENCE

the DNA to the condensed structure just like a finger holds a ribbon to a package as the bow is being made. Removal of the H1 histone before nuclease digestion also results in a DNAehistone complex but with only about 150 base pairs of DNA. This unit is called a core particle. Removal of the H1 leaves unprotected about 50 base pairs of DNA that link the core particles, hence the moniker linker DNA. Shown in Figure 4-7.2 is the image of a nucleosome that appears in

FIGURE 4-7.2 First-order folding: the nucleosome. Shown in this cartoon is the basic structure of the nucleosome. The eight interior blue balls represent two copies each of the histones H2A, H2B, H3, and H4, The bright red ribbon represents the core DNA of approximately 150 base pairs of DNA, and the dark red ribbon represents the linker DNA, which completes the total of approximately 200 base pairs in the repeat unit. The green pebble represents the external histone H1 that "places a thumb" on the DNA ribbon. The H1 histone protects the nucleosome structure. Removal of the H1 prior to nuclease digestion results in a core particle composed of the inner histones about which 150 base pairs of DNA are wrapped. The string of core particle units connected by the linker DNA has the appearance of a "string of pearls." Source of image: Wikipedia Creative Commons.

the Wikipedia article "Nucleosome." This model is exactly that proposed in the Van Holde, Sahasrabuddhe, and Ramsay-Shaw paper. A major difference is that the image in the van Holde et al. paper shows the double helix nature of the DNA with its major and minor grooves being embraced by the histones like a grandmother hugging her grandson she hadn’t seen in a week. The first-order structure of chromatin is a "beads-on-a-string" structure as shown in the electron micrograph in Figure 4-7.3. The first-order folded structure gives a 1/6 contraction in length.

4-7.2 DNA: Second- and Third-Order Folding The second-order folding of DNA requires some additional help from the class of histones: the histone H1 that protects the linker DNA. Given the "momentum of the turn" of the DNA on the nucleosome, it is not unexpected that the second-order folding continued in a helical pattern.

FIGURE 4-7.3 String-of-pearls structure of DNAehistone complex. The image is an electron micrograph of decondensed chromatin obtained from chicken erythrocytes. The decondensed chromatin of DNAehistone units separated by bare DNA has the appearance of a "string-of-pearls" structure with a diameter of 11 nm. The black brackets highlight the individual nucleosomes; black arrowheads point to nucleosome core particles, white arrowheads to the linker DNA (the string). Scale bar: 50 nm. Source: Wikipedia Creative Commons.

What results is something like a concertina, or squeeze box. At relatively low ionic strength (salt solution), the helical structure is expanded, whereas it contracts as the ionic strength is increased. The contracted solenoid structure is shown in Panel A of Figure 4-7.4. This is the 30-nm fiber structure, which is rigid up close but is flexible when viewed further away. Panel B has

A

B

FIGURE 4-7.4 Second-order folding: the 30-nm fiber. The "string of pearls" of core particle units and linker DNA forms a second-order helical structure. In the absence of histone H1, the diameter and helical repeat is sensitive to the ionic strength of the solvent because of exposed phosphate groups. The histone H1 neutralizes the repulsive interaction. A: The DNAehistone complex helical structure as a tight solenoid fiber. B: The DNAehistone complex helical structure in four acts. The top row is the view from the side of the fiber and the bottom row is the view from the end of the fiber. The numbers 177, 187, 197, and 207 are the number of base pairs in the repeat unit. Source Panel A: Wikipedia Creative Commons/Author Richard Wheeler. Source Panel B: Wikipedia Public Domain/Author Julien Mozziconacci.

780

4. LIFE SCIENCE

four-folded structures for the third-level folding. The nucleosome units are assumed in favor of a simpler ribbon representation. The features of the solenoid are evident.

4-7.3 The Ultimate DNA Folding: Chromosomes The DNA must be packaged in the cell in such a way that the genetic code can easily be read. There has to be some structural feature that allows the DNA to be unwound at the primary level but also at the highest folded level. The unwinding process cannot be spontaneousdthere has to be a trigger at the precise location to make available the necessary process. If the DNA is covered with proteins, then the charge is neutralized and the DNA structure collapses for the desired flexibility. A spherical structure is not desirable because of the inaccessibility to the interior information. A hint to a possible desired structure is the old churches that are highly rectangular and narrow. By placing windows along the longer walls, most of the church would be well lit during the services. Similarly, access to the DNA would be much easier if the ultimate structure was elongated. Shown in Figure 4-7.5 is a fluorescence microscopy image

FIGURE 4-7.5 The human chromosome. Metaphase chromosome from a female human lymphocyte stained with Chromomycin A3, using fluorescence microscopy. Source: Wikipedia Creative Commons.

of metaphase chromosomes from a female lymphocyte. Shown in Figure 4-7.6 is a graphic representation of the 23 chromosomes of the human genome. It is this information that has to be read.

4-7.0 THE PACKAGING OF THE GENETIC INFORMATION

781

FIGURE 4-7.6 The human genome. This is a graphic representation of the idealized human diploid karyotype. The figure shows the organization of the human genome into chromosomes. The lower right end shows the female (XX) and male (XY) versions of the 23rd chromosome pair. Source: Wikipedia Public Domain.

Shown in Figure 4-7.7 is a schematic diagram of the major events in mitosis (cell division), and in Figure 4-7.8 is an illustration pointing out the major parts of a replicated and condensed metaphase eukaryotic chromosome.

FIGURE 4-7.7 Major events in mitosis. Source: Wikipedia Public Domain.

782

4. LIFE SCIENCE

FIGURE 4-7.8 Scheme of a chromosome. 1): Chromatid, one of the two identical parts of the chromosome 2): Centromere, the point where the two chromatids touch and where the microtubules attach 3): Short arm 4): Long arm Source: Wikipedia Creative Commons.

Our excursion into the cell interior begins with the cell walls. The molecules that make up the walls of the cell and units that transport material are the amphiphiles.

4-8.0 The Amphiphiles Biological systems utilize polar, charged, and hydrophobic molecules. How can life function if it has molecules that differ so widely in polarity? The answer given by nature: use molecules that have the characteristics of the extremesdthe amphiphiles. The word amphiphile comes from the Greek: amphis, meaning both; and philia, meaning love. An amphiphile is defined as a chemical compound possessing both hydrophilic (water loving) and lipophilic (fat loving) properties. To have life, one must have phospholipids. As the name implies, a phospholipid has phosphate and lipid groups, as shown in Figure 4-8.1, as part of a membrane. Life utilizes phospholipids to form bilayer spherical objects (vesicles), enclosed spherical objects (micelles), and planar bilayer sheets as shown in Figure 4-8.2 (a liposome is a form of a vesicle).

783

4-8.0 THE AMPHIPHILES

Extracellular Space hydrophilic head

hydrophobic tail

Lumen of Cell

Phospholipid

FIGURE 4-8.1 Structure of the phospholipid molecule. The phospholipids are amphiphilicdloving both water and organic environments. The phospholipids have charged phosphate groups at the polar head and hydrocarbon chains at the tail end. The hydrophobic tail can be saturated or unsaturated hydrocarbon chains. Source: Wikipedia Creative Commons.

FIGURE 4-8.2 Phospholipid structures in an aqueous medium. The cross sections show three different structures the phospholipids can take on when in an aqueous medium. Source: Wikipedia Public Domain.

784

4. LIFE SCIENCE

4-8.1 Vesicles A vesicle is a spherical structure that encapsulates water. Vacuoles are vesicles that contain a lot of water. In plants, large vacuoles are used to control the osmotic pressure and nutrient storage. Lysosomes are involved in food digestion. Food vacuoles fuse with lysosomes, which break down the components so that the cell can utilize the components. Vesicles also transport molecules between locations inside the cell. Vesicles also serve to transport wastedthe secretory vesicles. Secretory vesicles are also used to store chemicals and then release them as needed.

4-8.2 Micelles Micelles can be thought of as a sheet folded back onto itself. Which way it folds depends on the surrounding medium. In an aqueous medium, a micelle has the hydrophobic chains on the inside with the polar heads on the outside. However, if the solvent is organic, then the components of the micelle are reverseddhence the name reverse micelle. The polar heads are interior, and the hydrophobic chains are exterior. Cartoons of a micelle and a reverse micelle are shown in Figure 4-8.3.

micelle

reverse micelle

FIGURE 4-8.3 Micelle and reverse micelle structures. The basic principle is that the outer portion of the spherical monolayer structure of phospholipids depends upon the solvent medium. In an aqueous medium the polar heads are at the surface in the formation of micelles. In an organic medium the reverse is true: the hydrophobic tails form the surface. Source: Wikipedia Creative Commons.

Micelles and reverse micelles function as taxi cabs. To transport an oily substance through a polar solvent the hydrophobic ends of the phospholipid surround the substance. The oily substance can now take a ride through the polar solvent. Likewise, a reverse micelle gives a polar substance a ride through an oily medium.

4-8.3 Bilayer Sheets A bilayer sheet has polar surfaces with oily interiors. Cell walls are made of bilayer sheets, as illustrated by the cartoon in Figure 4-8.4. The oily interior is a barrier for polar substance to enter or to leave. There are special mechanisms to "cross the River Styx" when necessary.

4-9.0 THE WORKER MOLECULES

785

q q q q q q q q q hydrophobic

oily interior q q q q q q q q

FIGURE 4-8.4 Phospholipid bilayer structure. The polar head of the phospholipid can structure water in the vicinity of the polar head of charge q. The bilayer structure has polar surfaces with an oily interior.

4-9.0 The Worker Molecules Life is a high-maintenance operation. It is like the Winchester House in San Jose but with a building plan. There are constant activities of building and repair in the cell. There must be a security force to thwart off invaders. It is not feasible to spotlight each activity in the cell in the present endeavor. Only a select few are summarized in this section.

4-9.1 Adenosine Triphosphate: The Energy Molecule Just as humans like portable energy sources, so do living organisms. One mobile source is adenosine triphosphate (ATP). The synthesis of the ATP molecule is done in the "power factory" called the mitochondria (Figures 4-6.2 and 4-6.3). The structure of ATP is shown in Figure 4-9.1. It is the third phosphate bond that has the portable energy.

FIGURE 4-9.1 Adenosine triphosphate (ATP) structure: the energy molecule. ATP is the portable energy unit of the cell. The third phosphate group is attached to the rest of the molecules with a high energy bond, which provides the energy to perform work in the cell. The line structure of ATP was modified. Source (Line Structure of ATP): Wikipedia Creative Commons.

786

4. LIFE SCIENCE

ATP is in the active transport of molecules and ions across the membrane barrier. The sequence of events is illustrated in Figure 4-9.2. The membrane has embedded in it a channel protein that extends through the membrane. In Panel 1, the item to be taken across the barrier is the blue oval.

1

2

3

P

ATP

P

ADP

ATP

P

P

ATP

6

5

4

FIGURE 4-9.2 Active transport: adenosine triphosphate (ATP) at work. Active transport across a membrane involves a channel protein and an energy molecule. The ATP molecule provides the energy for a conformational change in an embedded channel protein. The blue and lavender ovals represent ion, a group of ions, a molecule, or a group of molecules that are to be transported across the barrier. This is one scenario. 1) The blue oval is in position to be transported and the ATP is poised in position. 2) The bond for the third phosphate group is broken, resulting in a conformation change at the site closing the door on the blue oval in this transition step, and a removal of ADP. 3) The gate on the other side is opened, allowing the blue oval to be released. 4) The lavender oval enters into the site and triggers the release of the bound phosphate group. 5) Entrance of the lavender oval triggers a conformational change in the channel protein. 6) An ATP molecule attaches itself to the channel protein, which "resets" the conformation of the channel protein that releases the lavender oval.

The item can be an ion, a group of ions, a molecule, or a group of molecules. The ATP molecule is poised to provide the necessary energy for a conformational change in the channel protein to allow passage. In Panel 2, the high energy bond is severed and adenosine diphosphate (ADP) is released. In Panel 3, the gate is opened on the other side of the membrane and the item is free to explore the other side. The phosphate holds the gate open. The reverse process now takes place to transport an item, this time the lavender oval. Once the item is in the channel (Panel 4), the phosphate leaves the gate, and the gate is closed (Panel 5). Another ATP molecule comes along and opens the gate on the other side, and the item passes through to the other side (Panel 6). The ATP molecules are rejuvenated in a similar way, as illustrated in Figure 4-9.3. Shown on the left of this figure are two representations of the ADP molecule: the line model and the

4-9.0 THE WORKER MOLECULES

787

FIGURE 4-9.3 Regeneration of adenosine triphosphate (ATP). The molecule ADP (left side) is converted to ATP (right side) by means of the reaction involving the membrane-bound catalyst ATP synthase. Source of line figures and ball-and-stick figures: Wikipedia Creative Commons. Source of ATP Synthase cartoon: Wikipedia Public Domain.

ball-and-stick model. The enzyme ATP synthase is embedded in the membrane and serves to transport the hydrogen ion involved in the reaction. One the right-hand side is two representations of the ATP molecule: the line model and the space-filling model.

4-9.2 Enzymes Equilibrium thermodynamics provides information about the energy difference between the reactant side of the equation and the product side of the equation. The rate at which reactants become products is in the area of chemical kinetics. For a reaction to occur, the reactants must overcome an energy barrier that is set up by the bond energies and the repulsive energy between electrons of the participating molecules. If this energy is very high, then the reaction is very slow. A catalyst is an atom or molecule that lowers the energy barrier but is not used up in the reaction. Platinum, for example, is a catalyst for reactions that involve hydrogen. An enzyme is a biological catalyst. Enzymes differ from platinum as a catalyst because enzymes have a three-dimensional structure that imparts a fair degree of specificity to the reaction in which it can participate. That is, the reacting species must "fit" into the contours provided by the enzyme structure. A cartoon illustrating this requirement of an enzyme is shown in Figure 4-9.4. The enzyme has an "active site" in which a substrate (reacting particle) "fits" into the cubby hole of the enzyme. The enzyme changes shape to accommodate the binding process. The reaction portrayed in this cartoon is simplified to a unimolecular reaction severing the bond(s) that hold two units together. The bond is broken, the two parts leave, and the enzyme is no different than it was before the reaction. The suffix "-ase" reveals that the biological molecule is an enzyme. In Figure 4-9.3, the membraneembedded enzyme is ATP synthase: a clever word indicating it is an enzyme used in the synthesis of the ATP molecule. Similarly, DNA polymerases are enzymes that polymerize deoxyribonucleotides into DNA molecules.

788

4. LIFE SCIENCE

FIGURE 4-9.4 Enzyme action. The specificity of enzymes depends on the geometry of location of the active sites. Shown in the above cartoon is a schematic representation of a substrateeenzyme interaction that leads to the products. Source: Wikipedia Public Domain.

Allosteric Enzymes Enzymes sometimes act as their own regulators. Such enzymes are known as allosteric enzymes. One such enzyme is aspartate transcarbamoylase (also known as aspartate carbamoyltransferase), abbreviated ATCase. ATCase is a complex of 12 subunits, each subunit composed of six catalytic units (C) and six regulatory units (R). The catalytic units form trimers (C3), and the regulatory units form dimmers (R2) ATCase catalyzes the first step in the pyrimidine biosynthesis pathway, as shown by the cartoon in Figure 4-9.5. The action of ATCase is regulated by the end product of the pyrimidine pathway, cytidine triphosphate (CTP). The CTP produced by this reaction binds to the R sites on the ATCase and slows down the reaction (https://en. wikipdia.org/wiki/Aspartate_carbamoyltransferase). A three-dimensional model and ball model of ATCase are shown in Figure 4-9.6.

ATCase

carbamoyl phosphate

carbamoyl aspartate O

O O

NH2

O

Pi

aspartate

FIGURE 4-9.5 ATCase reaction. The enzyme aspartate transcarbamoylase (ATCase) catalyzes the reaction to form carbamoyl aspartate.

789

4-9.0 THE WORKER MOLECULES

A

B

FIGURE 4-9.6 The allosteric structure of ATCase. A: Aspartate carbamoyltransferase from Escherichia coli. B: Ball model of ATCase showing the relative locations of the catalytic (C) and regulatory (R) subunits. Source Panel A: Wikipedia Creative Commons. Source Panel B: Wikipedia Public Domain.

Enzymes in the Replication of DNA In the replication of DNA during cell division, a collection of enzymes are required. A specific location in the DNA is at the starting point. Topoisomerase puts the "swivel" in the unwinding DNA process. DNA helicase breaks the hydrogen bonds down the center of the DNA, creating a replication fork. A schematic diagram of the overall process is shown in Figure 4-9.7, and a "close-up" view of the replication process is shown in Figure 4-9.8.

DNA-ligase

DNA primase RNA primer

DNA-Polymerase (Polα) 3’ Lagging strand 5’

3’

Okazaki fragment 5’ Leading strand

5’ Topoisomerase

3’ DNA Polymerase (Polδ) Helicase Single strand, Binding proteins

FIGURE 4-9.7 DNA replication. DNA replication is the process of duplicating DNA. The identities of the important components are indicated in the figure. Starting on the right and moving leftward, the double-stranded DNA is unwound, the hydrogen bonds are broken at the replication fork, the DNA is primed, and the complementary bases are paired on each of the two new strands, and the operation is sewed up. Source: Wikipedia Public Domain.

790

4. LIFE SCIENCE

DNA polymerase

A

nucleoside triphosphate

B

FIGURE 4-9.8 DNA replication fork.

A: Stylized DNA replication fork with nucleotides match with the 50 / 30 synthesis shown. B: Diagram of DNA polymerase extending a DNA strand and proof-reading. Source Panels A and B: Wikipedia Creative Commons/Credit: Madeleine Price Ball.

4-10.0 Ions and Polyions Both small ions and polyions play a role in biological systems. Biopolymers may be composed of many units that are charged. For flexible biopolymers, the charge on the groups can play a major role in the conformation of the biopolymer. For rigid biopolymers, such as globular proteins, the charge distribution provides a geometry that may be more recognized by some molecules more than others. This "jigsaw puzzle" fit may lead to very strong bonds between the two molecules.

4-10.0 IONS AND POLYIONS

791

There are three characteristics of small ions that make them invaluable in biological systems. The two obvious characteristics are the size and charge. The third is the electron configuration of the ion that enables the ion to form covalent bonds. One way to characterize ions is with the combination of size and charge in the calculation of the surface charge density, denoted by s. Ions with high charge density can bind more strongly to biopolymers than those ions of lesser charge density. An example is denatured DNA at high temperatures. In low concentrations of sodium chloride the DNA single strands remain in solution. But when the concentration of sodium chloride is increased to 1.0 M, the single-stranded DNA precipitates. This is because of the very low level of divalent magnesium ions that are in sodium chloride. The surface charge density of magnesium ions is high enough to maintain a network of cross-linked single DNA strands even at the elevated temperature. Water also has an effect on the conformation of DNA. One might not think of water as charged, and it is not. But it does have a permanent dipole moment that does interact with DNA. The double-stranded DNA molecule is highly hydrated. Where do the small ions come in? Salt is a dehydrating agent, which means that it can disrupt any local water structure. High concentrations of salt (4 M) can convert right-handed B-DNA into left-handed Z-DNA. Three forms of DNA are presumed to be biologically active: A-DNA, B-DNA, and Z-DNA. Note that the "bulk" concentration of salt is not as important as the "local" concentration of salt. It is well known that trivalent and high ions cause DNA to "collapse" into a toroidal structure. Likewise, the association of divalent ions may result in a change in the secondary structure of DNA. Multivalent ions may also cause conformational changes in a molecule through a "bridging" attraction between two charged units in a molecule. Biopolymers whose stiffness is a result of internal repulsion of its charged groups become more flexible when multivalent ions bind strongly to the groups. Some enzymes need bound ions so that they can perform their function as a catalyst to a reaction. Such ions are referred to as coenzymes. Sometimes the atomic orbital arrangement of the ions aids in the function of the ion in biological systems.

Ion Interactions and Hydration Shells A high surface charge density can stabilize a hydration layer to thermal agitation. Ions with a high surface charge density can polarize the water around the ion to an extent that the hydration layer can be several solvent particles thick. Because of the thickness of the hydration layer, ions that are small in radius may actually find more resistance to movement through the solvent than larger ions with less charge. A cartoon illustrating the effect of surface charge density on the thickness of the hydration shell is given in Figure 4-10.1. When an ion interacts with a biopolymer, the process involves the removal of the hydration water and then the placement of the ion at the binding site of the biomolecule. The hydration energy is correlated with the size of the bare ion for identical charges. The hydration free energy of Naþ is 72 kcal/mol, whereas for Kþ it is 55 kcal/mol.

792

HH O HH O

HH O

HH O HH O

+3 HH O HH O

H H O

H O

H O

HH O

H O

H

H

+1

HH O HH O

H

HH O

H H O H H O

4. LIFE SCIENCE

HH O

FIGURE 4-10.1 Hydration layers. The size of the þ1 ion is smaller than the size of the þ3 ion. What this means is that the surface charge density of the þ1 ion is smaller than that of the þ3 ion. The higher surface charge density can attract more water molecules by orienting their dipole moments. The net effect is that as the ions move through the solvent the apparent size of the þ3 ion is larger than the þ1 ion.

It must be emphasized that these ions are part of a dynamic system in which the relative concentrations of all the molecules are constantly changing by participation in reactions and in intakeeoutput of chemicals in the system. Therefore their role in living systems functions as being in competition with other ions in their place in the biochemical system.

Ions, Conformation, and Selectivity Ion-carrying transport antibiotics may distinguish between Naþ and Kþ because of this difference in hydration energy. The general structure of these antibiotics is a "donut" shape with the ion interacting with the oxygen atoms of the molecule. Since oxygen atoms may be considered to be "electron withdrawing," these atoms have a slight negative charge to attract the positively charged sodium or potassium. However, because of the larger energy of hydration, it is more energetically favorable to select Kþ over Naþ.

4-11.0 The Central Nervous System The brain is the central monitoring and control system of the body. If one falls and scrapes a knee, the brain receives a pain signal and then sends a signal to the "repair team" to repair the broken skin and stop any bleeding. How is this information generated and sent to the appropriate locations in the body? The answer is that the signal is sent through the central nervous system by electrical impulses.

4-11.1 The Sodium/Potassium Ion Pump: Against the Grain The Naþ/Kþ pump is an exchange program. For every three Naþ given, there are two Kþ taken in return. This does not seem right because not only is a charge differential being built up but there are also concentration gradients being established.

793

4-11.0 THE CENTRAL NERVOUS SYSTEM

The Naþ/Kþ pump is working against entropy. Or so it seems. To move any system away from an equilibrium position, work must be done. To do work, it requires energy. And here is where the portable energy used by biological systems comes into play: ATP. A membrane-bound protein provides the pump action for active transport of sodium and potassium ions across the border. The energy that drives the pump is the third phosphate bond of ATP. Consult Figure 4-9.2 while reading the following description of the sodium/potassium pump. The pump, with bound ATP, binds three intracellular Naþ ions. ATP is hydrolyzed, leading to phosphorylation of the pump at a highly conserved aspartate residue and subsequent release of ADP. A conformational change in the pump exposes the Naþ ions to the outside. The phosphorylated form of the pump has a low affinity for Naþ ions, so they are released. The pump binds two extracellular Kþ ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the Kþ ions into the cell. The unphosphorylated form of the pump has a higher affinity for Naþ ions than Kþ ions, so the two bound Kþ ions are released. ATP binds, and the process starts again. A cartoon of the sodium/potassium pump is shown in Figure 4-11.1. The energy of the "third phosphate" in ATP is the source of the work necessary to increase the concentration gradients between the two sides of the membrane. This is an active transport mechanism that cost the energy of the ATP molecule. The buildup of a charge differential between the inside and outside of the cell is illustrated in Figure 4-11.2. It might be asked: Okay, what’s it good for? To which someone might respond: You’ve got some nerve. What the sodium/potassium pump is good for is to build up a "resting potential" for a nerve cell.

ATP q q

q q

q

3Na

q

q

+

q q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

2K+ ADP + P q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

FIGURE 4-11.1 Cartoon of the sodium/potassium pump.

794

4. LIFE SCIENCE

FIGURE 4-11.2 Sodium/potassium pump and buildup of charge. Using energy from ATP, three sodium ions are transported through the membrane to the extracellular space along with two potassium ions to the cytoplasm. This leads to a build up of concentration and charge gradient. Source: Wikipedia Creative Commons.

4-11.2 The Nervous System A schematic representation of a neuron is shown in Figure 4-11.3. There is a communication between the neurons. First, there is electrical excitation. There are voltage gradients across their membranes. Metabolically driven ion pumps are embedded in the membrane to provide ion dendrite

soma

axon terminal

node of Ranvier axon Schwann cell

nucleus myelin sheath

FIGURE 4-11.3 Anatomy of a nerve cell.

795

4-11.0 THE CENTRAL NERVOUS SYSTEM

channels. This sets up concentration differences. If the voltage changes by a large enough amount, an all-or-none electrochemical pulse called an action potential is generated. The action potential travels rapidly along the cell’s axon and activates synaptic connections with other cells when it arrives. A cartoon illustrating these actions is given in Figure 4-11.4. Panel B is a cartoon that shows how the charge is transferred across the synapse. The synapse is the junction between two nerve cells. There is a tiny gap separating the two. When an impulse is received, chemical substances are released, which diffuse across the junction. This causes an impulse to another nerve cell.

action potential

A action potential

action potential

B

FIGURE 4-11.4 Nerve cells in action. A: Nerve cells pass the electric impulse by means of an action potential. B: Passage of electrical impulse is through chemical reactions at the synapse. Source of image in Panel B: Wikipedia Creative Commons/Credit: By Thomas Splettstoesser (www.scistyle.com) - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid[41349545.

796

4. LIFE SCIENCE

4-12.0 Heavy Metal Ions: Required The definition of "heavy metal" is not well established. It may be based on density (the nucleus) or chemical behavior (the type of orbitals involved). The fuzzy definition of the term "heavy metal" is ideally suited to be used for something one does not understand to enter into intelligent conversations with others who used the term for the same reason. The term "heavy metal" takes on the same historical significance as "gravity" when Newton first coined the word. We don’t know what it isdbut it works. However, in the context of the subject matter of this chapter, the term "heavy metal" encompasses all elements that in some way are either beneficial or toxic to the human frame. The human body requires certain metals for structural strength or metabolic reactions. The most common metals are calcium (Ca), iron (Fe), magnesium (Mg), molybdenum (Mo), and zinc (Zn). Also required but in minute amounts are cobalt (Co), copper (Cu), nickel (Ni), and chromium (Cr). It is generally known that calcium is required for bone structure. Lesserknown uses are the lesser-known elements. Molybdenum, for example, is a cofactor for some enzymes.

4-13.0 You Are What You Eat Plants and animals are not born with a fixed amount of energy that will be needed throughout their lifetimes. Humans do not have to partition their activities so that there will be enough energy to fulfill necessary tasks. One need not curtail exercising out of fear that the energy of exercising reduces the amount of energy to perform other tasks. We do not eat food because it tastes good; we prepare food to taste good because we have to eat. We have to eat to "recharge our batteries"dreplenish our energy storehouse.

4-13.1 The Digestive System Food is a source of energy because of the chemical bonds. Food in the form that we eat is not of any direct value to the energy needs of a body. The food has to be broken down to its fundamentals, and then the body reassembles the molecules to meet the demands of the body. The body has specialized organs to meet these needs, which are illustrated in Figure 4-13.1.

The Mouth The first line of chemical attack on food is the point of entry into the body, the mouth. Teeth are located in the mouth for a reason: to grind the incoming foodstuff. Why is that necessary? The answer lies in the dissolution of sugar. Which dissolves the fastestda lump of sugar or powdered sugar? The teeth break the food into smaller chunks to facilitate digestion. Located in the mouth are the salivary glands. The salivary glands mix with the incoming food as the first stage of digestion. The mouth, therefore, is where a physical and chemical attack on the food that is eaten occurs.

The Esophagus The food in the mouth has to go to the main digestive organdthe stomach. From the mouth to the stomach is approximately half the height of the body. When the food is swallowed, it enters the

797

4-13.0 YOU ARE WHAT YOU EAT

mouth

salivary glands

esophagus

liver

stomach pancreas

large intestines

small intestines

rectum FIGURE 4-13.1 Major components of the digestive system. Source: Wikipedia Creative Commons.

esophagus. Not content to rely on gravity, there are a series of muscular contractions to force the food along its way. These muscular movements are called peristalsis. Muscle contractions are a good thing because gravity works the wrong way if one eats upside down, such as hanging from a tree limb.

The Stomach The partially digested food now enters the stomach for some serious digestion procedures. The stomach is the flask in the chemistry lab in which chemical reactions are confined. The digestive fluid is composed of hydrochloric acid, sodium chloride, and potassium chloride. The parietal cells in the gastric glands produce the acid. The stomach has an acid content of approximately 0.01 M, or a pH on the order of 2. The acidity of the stomach is maintained through a proton pump, Hþ/Kþ ATCase. The enzyme pepsin is activated by the acid. Pepsin helps to break the

798

4. LIFE SCIENCE

chemical bonds of the foodstuff. The gastric fluid is buffered by the introduction of bicarbonate when needed. Otherwise, the stomach may become too acidic. Cells that produce the bicarbonate also produce mucus to line the stomach for protection from the acid.

The Pancreas The pancreas secretes enzymes into the duodenum. In preparation for the small intestines, the enzymes break down the fats, carbohydrates, and proteins. The pancreas also produces bicarbonate.

The Small Intestine The small intestine is where the components of the foodstuff are absorbed, which eventually finds its way into the body. For maximum absorption capabilities, it is desirable to have a large surface area that obtains with a small diameter tube. Hence, the adjective small is applied to this intestine. To increase the surface area for maximum absorption as the foodstuff passes through the digestive system, the small intestine is about 22 feet in length. The small intestine is made up of the duodenum, jejnum, and the ileum. As muscle contractions move the contents along, it is mixed with digestive secretions from the pancreas and the liver. The duodenum is the main location of action for the breakdown process with the jejunum and ileum being responsible for the absorption of nutrients into the bloodstream. Muscle contractions help to mix the contents as they move the digested food along.

The Liver The liver processes the nutrients that the small intestine absorbed. The liver is the "chemical factory" of digestion. It makes all of the chemicals the body needs and takes out the potentially harmful chemicals (detoxification).

The Large Intestine The large intestine, or colon, has evolved to take care of the waste of the digestion process. The large intestines are shorter that the small intestines (6 feet) but larger in diameter. The waste is processed so that it is easier to be emptied into the bowels. The waste is first in the liquid state but ultimately becomes solid.

The Rectum The rectum connects the colon to the anus. The rectum plays the role of a "holding tank" for the stool. It sends a message to the brain that the digestion process is complete, and the waste is ready for evacuation.

4-13.2 Metabolism Metabolism is defined as the set of chemical processes that occur within a living system that are necessary for the maintenance of life. Metabolism is the process that converts the fuel in the food

4-13.0 YOU ARE WHAT YOU EAT

799

we eat into energy, the body can use. To metabolize is to produce a substance by metabolism. A metabolite is the substance that is produced by metabolism. There are two types of metabolic reactions: anabolism (building up) and catabolism (breaking down). Anabolism starts with the parts and makes a larger molecule; catabolism starts with the large molecules and makes smaller molecules. When Mary Poppins sings the lyrics "A spoonful of sugar that makes the medicine go down" in the Walt Disney 1964 production, the sugar also undergoes metabolism in the body. Because all metabolic systems tap into the same pool of chemicals, all specific metabolic systems are interconnected. Some of the interconnections are shown in Figure 4-13.2.

FIGURE 4-13.2 The carbohydrate metabolism connections. The above diagram shows the relationship between the processes of carbohydrate metabolism, including glycolysis, gluconeogenesis, glycogenesis, glycogenolysis, fructose metabolism, and galactose metabolism. Source: Wikipedia Creative Commons.

4-13.3 Metabolic Pathways A metabolic pathway is defined as a sequence of chemical reactions catalyzed by enzymes that occur within a cell. Metabolic pathways can be quite involved. One of the more familiar metabolic pathways is the Krebs Cycle (citric acid cycle), shown in Figure 4-13.3. This image is to illustrate the complexity of a metabolic system, and not for a detailed discussion of the Krebs Cycle. Why must there be a sequence of reactions? Why not just go straight to the products, such as the burning of alcohol in an alcohol lamp? To answer these questions is the same as the difference between a slow leak and a blowout of an automobile tire. In the case of a blowout, the energy is released all at once and may result in an accident. If, on the other hand, there is a slow leak, one can still control the automobile and safely pull over to the side of the road. As indicated in the cartoon in Figure 4-13.4, a single-step reaction releases all of the energy at once, and the cell would die. On the other hand, if only a little energy is released at each step, the local energy released can be absorbed without harm.

800

4. LIFE SCIENCE

FIGURE 4-13.3 The Krebs Cycle. The purpose of this figure showing the Krebs Cycle is to illustrate the complicated nature of reaction pathways in biological systems. As noted by Wikipedia in the description of this image: "This is a featured picture, which means that members of the community have identified it as one of the finest images on the English Wikipedia, adding significantly to its accompanying article." Source: Wikipedia Creative Commons.

reactants

products

A

B

FIGURE 4-13.4 Reaction mechanism in baby steps. A: The thermodynamic energy difference between reactants and products. The amount of energy released in a onestep mechanism can be very large. B: Biological reaction pathways release the energy in smaller increments to prevent destructive releases of energy.

4-14.0 THE BIOLOGICAL RESPONSE TO TOXIC CHEMICALS

801

4-14.0 The Biological Response to Toxic Chemicals If one eats too much food, one can expect to get fat. But there comes to a point that too much of something can have very harmful effects to the body: the extreme in harm being death. There was once a study on the link of the soft drink Coca Cola to cancer. The study used mice. The conclusion drawn, when "up-scaled" to humans, was that if one drank 80 bottles of Coca Coal per day for a month, then one might develop cancer. What the report failed to note is that if a person drank that much water per day it would kill that person. Water is necessary for life, but too much water is deadly. It’s an "electrolyte thing," that does it. The term "toxic chemicals" refers to any chemical that is harmful to the body. This includes chemicals found in the kitchen, bathroom, work room, etc. The specific focus in this tome is chemicals that are introduced into the environment specifically because of their toxic nature. For example, para-dichlorodiphenyltrichloroethane (DDT) was used to control typhus and malaria in World War II among civilians and troops. The control was indirectdthrough the control of insects. There are two ways toxic chemicals can build up in a system. One way is for an animal to acquire toxic compounds by feasting on an animal or plant that has been contaminated. As a contaminated animal continues to eat other contaminated animals, the toxicity builds up. The "last man standing" may not be standing for long. This process is called bioamplification. The second way is if the animal or plant has a greater affinity for the toxic material than the surroundings. In other words, the concentration is greater in the animal than the surrounding. This phenomenon is called bioconcentration.

4-14.1 Bioamplification Bioamplification is defined as the increasing of the concentration of a substance in the tissues of organisms at successively higher levels in a food chain. The term "food chain" in this context means the sequence of feasts that can occur between species in the foods-ball. It is the order in which the species are eaten. From the point of view of humans, this means plants, fish, deer, cows, pigs, insects, chickens, and so forth. In other words, anything that can swim, fly, run, or crawl. What this means is that one has to take into consideration everywhere that a toxic substance can be found. This situation is symbolically represented in Figure 4-14.1. What does this diagram mean? Take as an example the spraying of field with a herbicide. There are droplets of the herbicide in the air which can blow anywhere. The herbicide reaches the surface of the ground. It covers the surface of plants that animals eat. Rainwater takes the herbicide underground where it might end up in aquifers and groundwater used for drinking. The rain might wash the herbicide into streams and rivers and eventually to the sea. Any plant and animal that has been exposed to the herbicide and then eaten is a contributor to bioamplification. The toxic contamination of spraying a field with herbicide pales compared with the massive use of insecticides, herbicides, and pesticides used on industrial farms. Consider also the massive amounts of water purposely made toxic for fracking operations in the oil industry that finds its way to rivers. Industrial waste of any kind should raise a flag.

802

4. LIFE SCIENCE

solid air

liquid

water

so l i d solid

surfaces FIGURE 4-14.1 Connective diagram of toxic substance locations. Toxic substances are not confined to the locations where they are generated. Air and water are good carriers of substances and are instrumental in distribution of the bad along with the good. The arrows indicate transport in both directions between phases.

4-14.2 Bioconcentration Bioconcentration is the accumulation of a substance resulting from passage from one phase into another phase. The bioconcentration factor (BCF) is the ratio of equilibrium concentrations of specific chemical between two phases. This situation is symbolically represented as

α Cα

β Cβ

where Ca is the concentration in the a phase and Cb is the concentration in the b phase. The BCF for this system is simply; BCF ¼

Cb Ca

[4-14.1]

4-16.0 TOXIC HEAVY METALS

803

Kidneys are organs in which bioconcentration applies. The kidneys perform osmotic work to concentrate the unwanted foodstuff for expulsion from the body. The hemorrhaging of crude oil in the 2010 explosion of Deepwater Horizon was the cause of concern for the fisheries in the area. Oysters, for example, have a BCF of 1000 when it comes to oil.

4-15.0 "We Have Met The Enemy, And They Are Us" "We’ve got to pause and ask ourselves. How much clean air do we need?" Lee Iacocca, Former Chyrsler Chairman, Former Ford President The title of this section comes from the Pogo comic strip written by Walt Kelly. The quotation of Lee Iacocca is proof of the comic strip statement of politics. Life is totally dependent on the air we breathe, the water we drink, and the food that we eat. It is true that accidents do occur, and toxic materials can be accidently released into the environment. It is also true that toxic substances may be inadvertently used in products put on the market. Lead was once used in pottery because of the yellow color it produced. The use of lead goes back to ancient times. But once the biochemistry was understood, lead was taken off the market. Yet there are some people who wantonly engage in activities that toxify the only three things that life depends on: air, water, and food (land). Corporations exist only for one reason: to make profits. To make profits means taking risks in regard to safety. To take risks it means to convince the public, in general, and the legislature, in particular, that there are no safety issues. To have free range to toxify the environment and our bodies is dependent upon a gullible citizenry. To quote Oliver Wendell Holmes: "Even a dog knows the difference between being kicked and being stumbled over." Oliver Wendell Holmes, Sr. Can we, as humans, recognize what dogs recognize? Apparently not, since there are those who try to convince the public that it is a good thing to deregulate the rules set up to protect the general public. How does the body respond to toxic chemicals? Do toxic chemicals enter into the food chain? Do toxic chemicals "stay put" or migrate?

4-16.0 Toxic Heavy Metals The list of heavy metals that are toxic to humans include mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), aluminum (Al), beryllium (Be), chromium (Cr), copper (Cu), nickel (Ni), and manganese (Mn). Most of these toxic metals should be very familiar because of our technology-based society. Mercury at one time was used in thermometers that could be purchased at a store. Lead used to be in paints, and tetraethyl lead used to be in the gasoline of our cars to prevent knocking. We use nickel-cadmium batteries on a daily basis. Clearly, these toxic elements seem to be of no concern to the general public. The reason is that toxicity depends upon the chemical form of the element. Take as an example the element mercury. Mercurous chloride, Hg2Cl2, is calomel, which is used as a laxative. Mercuric chloride, HgCl2, was once used as a disinfectant and a treatment for syphilis. Mercuric chloride is no longer used for medicinal purposes because of the toxicity of mercury (II).

804

4. LIFE SCIENCE

The ions Hg2þ, Pb2þ, and Cd2þ react with the sulfhydryl groupsdSH. These groups are present in enzymes and also serve as "cross-linking" groups. In the removal of the hydrogen the sulfhydryl group becomes negatively charged, R-SH ¼ R-S þ Hþ The divalent metal ion may now act in the formation of "bridges" between two such ionized sulfhydryl groups; R0 -SH þ R-SH þ M2þ ¼ R0 -S–M2þ–S-R þ 2Hþ The five heavy metals of concern are mercury (Hg); lead (Pb); cadmium (Cd); arsenic (As); and chromium (Cr). These elements exist in the following forms: • monovalent (Hg2Cl2), • divalent (HgCl2, PbCl2, CdSO4), • trivalent (As2O3), • tetravalent (PbO2), and • pentavalent (H3AsO4).

4-17.0 The Mercury Scare In the vicinity of the year 2005, a family restaurant in Kansas City was running a food special on fish and steak dishes. This was a bit of poor timing. This happened to be at the height of the scare about mercury in fish and the mad cow disease. Of the five main toxic heavy metals, only mercury can be said to accumulate through the food chain. The different forms of mercury are metallic (Hgo), mercurous (Hgþ), mercuric (Hg2þ), and covalent Hg(CH3)2 (the hybridization of the mercury bonds are 2p hybrid, which makes this a linear molecule). The following is a partial list of the sources of mercury. Mercury amalgams • Liquid mercury, silver, and tin used in dental work to fill cavities • Extraction processes for gold or silver • Sodium and mercury to convert sodium chloride to sodium hydroxide and chlorine Ionic mercury • Hg(NO3)2 used in hat industry to make felt hats ("mad as a hatter" in Lewis Carroll’s Alice in Wonderland) • HgS ore is very water insoluble and addition of Na2S can remove Hg2þ

4-17.0 THE MERCURY SCARE

805

Covalent mercury • HgCl2, Hg(CH3)2 • CH3HgCl and CH3HgOH (CH3Hgþ is highly toxic because it is soluble in fatty tissue and can cross the bloodebrain barrier and the human placental barrier) Mercury vapor (goes from lungs to bloodstream) • Fluorescent bulbs • "Dirty coal" power plants Mercury enters food chain through plants • Carrots, 0.2 ppm • Potatoes, 0.2 ppm • Mushrooms, 1 ppm Mercury enters food chain through fish (BCF ¼ 100,000 in surrounding water) • Ocean tuna • Ocean swordfish

4-17.1 Toxicity of Mercury The toxicity of mercury can be traced back to the Ancient Egyptians. The phrase "mad hatter" was coined in the 1800s because of chronic exposure to mercury of hat manufacturers. Short-chain organic mercury can attack the nervous system. Elemental mercury exhibits neurologic toxicity. It has the ability to penetrate the central nervous system, and if it gets ionized, it is trapped because ions cannot penetrate the oily barrier. Methyl mercury can interact with sulfhydryl groups that affects the ability of enzymes to function. Mercury in any form is toxic.

4-17.2 Where Has All the Mercury Gone, Long Time Passing? The distribution of the different forms of mercury is illustrated in Figure 4-17.1. One or another form of mercury enters the body by absorption, inhalation, or ingestion. The ingested mercury passes through the stomach, to the kidneys, to the liver, then to the spleen, and eventually to the brain. The neutral form of mercury and the modified mercury with a hydrocarbon chain can pass through the membrane barrier from the blood to the brain. Once in the brain, it can damage the nervous system. A cartoon indicating passage through the brain barrier is given in Figure 4-17.2. Eventually the mercury will find its way to the hair and nails. The chemical formula for methylmercury is CH3HgX. When ingested, the "X" of methylmercury is converted to a sulfur containing amino acid. As an amino acid, it can go where none have gone before.

806

4. LIFE SCIENCE

distribution of mercury

Hgo

air CH3HgCH3

Hg2+

water

Hgo

Hg2+

Hgo

Hg2+

CH3Hg+

CH3HgCH3

CH3Hg+

CH3HgCH3

H2S organic and inorganic complexes

FIGURE 4-17.1

q q

Distribution of mercury in the environment.

q q

q

q

q

sediment

HgS

q q

q

q

q

q

q

q

q

brain damage to the nervous system

q

q

q

q

q

q

q

q

Hg+ q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

q

Hg+ -(CH2)nCH3 q

q

q

Hg0

q

q

q

q

q

q

q

q

q

q

q

q

q

q

blood q

q

q

q

q

q

q

q

q

q

q

q

q

q

FIGURE 4-17.2 Mercury passage through the brain barrier. The brain barrier is the oily region in the membrane. Charged mercury (Hgþ) cannot move through the hydrocarbon chain interior, whereas elemental mercury (Hg0) has no electrical charge to prohibit its passage. Charged mercury attached to a hydrocarbon chain can pass through the barrier by riding on the back of the oil-soluble hydrocarbon chain.

4-18.0 GET THE LEAD OUT: DON’T BE FLINT-STONED

807

Mercury that finds its way to the brain interacts with the enzyme ATPase at its sulfhydryl group. This is the enzyme that rejuvenates the energy molecule ATP as shown in Figure 4-9.3. Because mercury inactivates the regeneration process of the energy molecule ATP, mercury clearly has a major effect on the central nervous system

4-18.0 Get the Lead Out: Don’t Be Flint-Stoned In 2014, a decision was made in Flint, Michigan, to change the source of drinking water. The decision was long time coming. During the period 1967e2013, the city planned to use the Flint River as a backup water source. A financial emergency was declared in 2011, which was a cause for a search for how to cut costs. On March 22, 2012, County officials announced plans for a new pipeline to be constructed to deliver water from Lake Huron to Flint, to which the city approved the KWA contract on April 16, 2013. The next day, Detroit, the source of water, terminated its water contract with Flint. Because of construction delays, a switch was made regarding the source of water. On April 21, 2014, the source was to be the Flint River. On August 14, 2014, the city advised the citizens to boil the water, then lifted the advisory on August 20, and advised them again to boil the water in September. The General Motors Flint Truck Assembly plant discontinued using Flint tap water during October 2014 because the water was corroding engine parts from the high levels of chlorine. Because of high water rates, City officials declined an offer on January 12, 2015, to be reconnected to Lake Huron water. January 12, 2015, the bottle brigade begins. Flint residents, complaining about health issues caused by city water, brought bottles of discolored water to a community meeting.

4-18.1 EPA and CDCP to the Rescue On February 26, 2015, EPA manager Miquel Del Toral detects lead levels in a Flint resident to be seven times greater than acceptable limits of the EPA. On June 24, 2015, Toral states in a memo that a team of scientists from Virginia Tech found extremely high lead levels in four homes. On September 8, 2015, the Virginia Tech water team reported that 40% of Flint homes have contaminated drinking water. On September 11, 2015, the Virginia Tech water team recommends that the State of Michigan declare the water in Flint is not safe for drinking or cooking. On September 24, 2015, pediatrician Dr. Mona Hanna-Attisha, of the Hurley Medical Center, released her study that showed an increased number of children with high lead blood levels after the switch to Flint River water. On February 16, 2017, the Centers for Disease Control and Prevention (CDCP) find the first genetic link from Legionnaires’ disease to the Flint water.

4-18.2 The "Official" Response On July 9, 2015, Flint Mayor Dayne Walling drinks Flint tap water on local television in an attempt to show the Flint water is safe. On July 13, 2015, a Michigan Department of Environmental Quality (MDEQ) official tells the Michigan Public Radio: "Anyone who is concerned about the lead in the drinking water in Flint can relax." On January 12, 2016, the Michigan National Guard is brought in to help distribute water in Flint. On March 16, 2017, Michigan Governor Rick Snyder created the Child Lead Exposure Elimination Commission to avoid future lead poisoning outbreaks.

808

4. LIFE SCIENCE

4-18.3 The Afterglow October 15, Michigan Governor Rick Snyder signs a bill for $9.35 million to put things back the way they weredto Detroit waterdand it was done the next day. Flint Mayor Karen Weaver declares a state of emergency on December 15. MDEQ Director Dan Wyant resigns on December 29. The above account is a very brief summary of the Flint River fiasco found in the Wikipedia account. In terms of printed pages, there are 96. In terms of references, there are 457. The timeline continues to January 12, 2018. Has the problem been resolved? To quote the two 2018 entries: "2018 January 8 - MDEQ official Eric Oswald, DEQ’s Drinking Water and Municipal Assistant Division director, tells the EPA he also has concerns about ’long-term, technical managerial and financial capacity’ to handle the responsibility and that ’the city faces numerous challenges in staffing its limited water treatment plant.’ January 12 - An MDEA study for the first half of 2017 claims 90 percent of water samples were at low ppb of lead, with an official stating the city’s ’water quality is restored’" What happened at Flint Michigan can happen anywhere at any time. When the Environmental Protection Agency came into existence during the Nixon Administration, there were very good reasons. One very good reason was that scientists were needed for their knowledge and expertise in specialized fields that could affect the health of the public. The general public does not have that extended knowledge, and those from industry have a conflict of interests. Another good reason is that it is in the interest of all to have a national agency to protect the public rather than a local agency that might have vested interests. This is clearly brought to light in the Flint experience when the MDEQ official went on the Michigan Public Radio on July 13, 2015. It is also in the best interests of government to see to it that a government agency be the watchdog by setting standards and monitoring industry practices. No agency is perfect because those who work at the agency are not perfect. What is important is the task of the agency because personnel change. If any administration seeks to relax the restrictions and regulation authority of an agency created to protect the public, then that administration is not working for the citizens. Ultimately, it is the citizens who must look after themselves by making sure public officials are informed with the interests of the people in mind.

4-18.4 Sources of Lead There are many sources of lead, but not as many as there used to be. Lead paint has been banned for sale, but some still exists on walls. At one time, toy trucks were made of lead. The following is a list of the sources of lead. Free element - Lead pipes

4-18.0 GET THE LEAD OUT: DON’T BE FLINT-STONED

809

Divalent lead - Storage batteries, 2Pb þ O2 þ 4Hþ ¼ 2Pb2þ þ 2H2O - Yellow pigment in pottery (PbO) if used incorrectly PbO þ 2Hþ ¼ Pb2þ þ H2O - Pigments: PbCrO4, yellow; Pb3O4, red; Pb3(CO3)2(OH)2 Tetravalent lead - PbO2 as an electrode in lead storage batteries Pb(s) þ PbO2 þ 2H2SO4 ¼ 2PbSO4 þ 2H2O Organic lead Tetramethyl lead once was used as an additive for "antiknock" engine performance Lead also enters the food chain through plants Cucumber, 24 ppb Cabbage, 16 ppb Sweet corn, 22 bbp Tomatoes, 2 ppb Apples, 1 bbp Most of the lead leaves the body undigested.

4-18.5 Lead in Bone Lead(II) is chemically similar to calcium. What this means is that these two ions are in competition for binding sites. The relative affinities for binding are not independent of the binding sites. There are sites in which calcium is the preferred ligand, and sites that would rather have lead. Small quantities of lead might replace larger quantities of calcium in activating key neurotransmitters (http://www.lead.org.au/lanv10n2/lanv10n2-11.html). Large quantities of calcium supplements may reduce the effect of lead. However, calcium may interfere with the absorption of iron. Bones consist of living cells imprisoned in a mineralized organic matrix. Bones have several functions in the body. The most obvious is giving a rigid structure of support, for mobility and giving protection for some of the organs, the lungs for example. Red and white blood cells are produced in the bones. The structure of a bone is shown in Figure 4-18.1. There are clearly different types of bone cells.

810

4. LIFE SCIENCE

Compact Bone & Spongy (Cancellous Bone) Lacunae containing osteocytes Lamellae Canaliculi

Osteon

Osteon of compact bone Trabeculae of spongy bone

Haversian canal

Periosteum Volkmann's canal

FIGURE 4-18.1 Structure of a compact spongy bone. Source: Wikipedia Creative Commons.

Bone rigidity arises from the honeycomb-like architecture, or matrix. The formation and the mineralization of the bone are the functions of the osteoblasts and osteocytes; flattened osteoblasts form the protective layer of the bone surface. The mineralized matrix has an organic phase and an inorganic phase. The organic phase is composed primarily of collagen fibers, a triplestranded polymer. Collagen is a protein found in the skin and in its purified form has commercial use in the cosmetic game. The basic unit of collagen is the protein tropocollagen. An electron microscopic image of collagen fiber is given in Figure 4-18.2.

FIGURE 4-18.2 Collagen fibers. Electron micrograph with 1000 times magnification of mineralized collagen fibers in bone. Source: Wikipedia Creative Commons.

4-18.0 GET THE LEAD OUT: DON’T BE FLINT-STONED

811

The inorganic phase is calcium phosphate. The structure of the inorganic phase is like hydroxylapatite: Ca10(PO4)6(OH)2. Pounds, Long, and Rosen give four ways in which lead intoxication can alter bone function: (1) indirectly through changes in circulating levels of hormones; (2) directly alter bone function by perturbing bone cell response to hormonal regulation; (3) impair ability of cells to synthesize or secrete components of the cell matrix; and (4) replacement of calcium in active sites of the calcium messenger system (https://www.ncbi.nlm.nih.gov/pubmed/2040247). Shown in Figure 4-18.3 is an X-ray of the effect of lead poisoning. A diagram of locations and symptoms of lead poisoning is given in Figure 4-18.4.

FIGURE 4-18.3 X-ray of bone with lead poisoning. The arrow points to dense metaphyseal lines. Source: Wikipedia Creative Commons.

812

4. LIFE SCIENCE

FIGURE 4-18.4 Anatomy of lead poisoning. The above figure shows location and tells the symptoms of lead poisoning in the human body. Source: Wikipedia Creative Commons.

4-18.6 Lead and Hemoglobin Synthesis Blood is the transportation medium for molecules in the system. Red blood cells use these "waterways" to deliver oxygen to the various parts of the body. The primary structural unit for carrying the oxygen is the porphyrin ring, shown in Figure 4-18.5. Oxygen and carbon

813

4-18.0 GET THE LEAD OUT: DON’T BE FLINT-STONED

FIGURE 4-18.5 The heme group. Source: Wikipedia Public Domain.

monoxide compete for binding to Fe(II). The first steps in the synthesis of the porphyrin ring are shown in Figure 4-18.6. The succinyl CoA reacts with glycine to give d-aminovulinate. The next step is given in Panel A of Figure 4-18.7. Two molecules of d-aminovulinate react in the presence of the enzyme d-aminoevulinate dehydratase to form porphobilinogen. Notice the relationship of porphobilinogen to the porphyrin molecule. If lead is present, then it interacts with the enzyme d-aminoevulinate dehydratase. The result is that the concentration of d-aminovulinate builds up.

COO| CH2 | CH2 | C-S-CoA || O Succinyl CoA

H+

+

NH3+ | CH2 | COO-

glycine

CO2 + CoA

COO| CH2 | CH2 | C-CH2 –NH3+ || O δ-Aminoevulinate

FIGURE 4-18.6 The first step in the synthesis of the porphyrin ring.

814

4. LIFE SCIENCE

A

COO| CH2 | CH2 | C-CH2 –NH3+ || O

+

COO| CH2 δ-aminoevulinate | CH2 dehydrase | C-CH2 –NH3+ || O +

COO| CH2 COO| | C CH2 | | C _________ C || || C CH N H CH2

H3 N

porphobilinogen

COO-

B

| CH2 | CH2 | C-CH2 –NH3+ || O

+

COO| COOCOO CH 2 | | | CH2 δ-aminoevulinate C CH2 | | | CH2 dehydrase C _________ C | || || C-CH2 –NH3+ C CH || N O CH2 H + H N 3

Pb

accumulates

FIGURE 4-18.7 Effect of lead on the synthesis of the porphyrin ring. A: The second step in the porphyrin ring synthesis brings together two molecules of d-aminovulinate to form porphobilinogen. B: Lead present in the system will react with the enzyme d-aminoevulinate dehydratase. The absence of this enzyme action means the reaction will not proceed, porphobilinogen is therefore not produced, and d-aminovulinate accumulates.

4-19.0 Pesticides The American Heritage Dictionary defines pesticide as: pesticide: A chemical used to kill pests, especially insects. The online dictionary.com gives as a definition: pesticide: A chemical preparation for destroying plant, fungal, or animal pests. The wording in this definition is ambiguous. One way to read this sentence is to use the distribution law of mathematics: destroying plant pests; destroying fungal pests, or destroying animal

4-19.0 PESTICIDES

815

pests. The ambiguity enters if someone considers the neighbor’s dog a pest. Wikipedia gives the following definition under "Pesticide": Pesticides are substances that are meant to control pests (including weeds). These definitions are circular arguments. The suffix "-cide" denotes something that kills. The word "pest" means the object to be killed is a pest. Notice that the extent of action is varied: "control," "kill," and "destroy." Wikipedia becomes more specific later in the article, giving a long list of specific -cides, such as herbicide, insecticide, rodentcide, fungicide, and so forth. Wikipedia also categorizes pesticides according to the target: herbicide/plants; algicides/algae; avicides/birds; insecticides/insects; bactericides/bacteria, and so forth. Wikipedia also gives the definition of pesticide by the Food and Agriculture Organization (FAO). The FAO definition is quite long because of the specifics addressed in the definition. Even though the pesticides are designed to target specific pests, the effects are not at all specific. The phrase "one for all and all for one" becomes "a poison for one is a poison for all."

4-19.1 Desirable Properties of Insecticides For an insecticide to be useful the concoction must have the following desirable properties: 1) must be stable against environmental degradation 2) must have low water solubility 3) must be highly soluble in hydrocarbon-like environments (such as fatty acids) 4) must have a relatively high toxicity to insects but low toxicity to humans Consider items 1) and 2) together. The insecticide will remain on the ground for a very long time. Since humans are larger than small animals, the longevity and locality of the insecticide can be harmful, if not kill, small animals. To be highly soluble in hydrocarbon-like environments means that farm animals might be harmed as well. What about the possibilities of biomagnification and bioconcentration?

4-19.2 Short List of Insecticides Insecticides are substances that kill insects. A short list of currently used insecticides around the home and their active ingredients include the following: • Raid e Ant and Roach Killer (imiprothrin, cypermethrin) • Hot Shot e Kitchen Bug Killer (pyrethrins, piperonyl butoxide) • Ortho e Flying Insect Killer (tetramethrin, phenothrin) • Spectracide PRO e Wasp & Hornet Killer (tetramethrin, permethrin, piperonyl butoxide) Of those listed, Spectracide PRO is the most potent.

816

4. LIFE SCIENCE

4-19.3 DDT DDT is an acronym for para-dichlorodiphenyltrichloroethane. DDT was first synthesized in 1874, but its insecticidal properties were not discovered until 1939. It was used to control typhus and malaria in World War II among civilians and troops. The 1948 Nobel Prize in Physiology and Medicine went to the Swiss chemist Paul Hermann Mu¨ller for his discovery of the high efficiency of DDT as a contact poison against several arthropods. DDT was used as an agricultural insecticide after World War II. The structure of DDT is given in three representations in Figure 4-19.1.

DDT

Cl Cl__C__Cl Cl __

__C__

__Cl

DDE FIGURE 4-19.1 The Structures of DDT and DDE. DDT, para-dichlorodiphenyltrichloroethane: line, ball-and-stick, and space filling models DDE, dichlorodiphenyldichloroethane: line and ball-and-stick models Source: Wikipedia Public Domain.

Overuse of DDT in the 1950s and 1960s gave rise of concerns that DDT affected the reproductive ability of birds. Rachel Carson became aware of the DDT issue from a New York Times report of the unsuccessful struggle to restrict DDT use in Nassau County, New York. William Shawn, editor of The New Yorker, encouraged Carson to write on the subject, which resulted in her book Silent Spring. In 1962, Rachel Carson wrote Silent Spring, where she referred to DDT as the "elixir of

4-19.0 PESTICIDES

817

death." Carson emphasized the Bald Eagle, whose dietary intake of DDT was very high. President Kennedy ordered his Science Advisory Committee to investigate Rachel Carlson’s claims. Trade names that DDT has been marketed under include Anofex, Cezarex, Chlorophenothane, Clofenotane, Dicophane, Dinocide, Gesarol, Guesapon, Guesarol, Gyron, Ixodex, Neocid, Neocidol, and Zerdane. The mechanism of action in insects is that it opens sodium ion channels in the neurons, the neurons spontaneously fire, and the spontaneous firing leads to spasms and eventual death. But there is evolution at work: insects developed a resistance to DDT. The insects metabolized DDT to noninsecticidal DDE.

Properties of DDT DDT is a crystalline solid, which is odorless and colorless. DDT is highly hydrophobic; nearly insoluble in water; and has good solubility in most organic solvents, fats, and oils. The breakdown products and metabolites are DDE (dichlorodiphenyldichloroethylene), and DDD (dichlorodiphenyldichloroethane).

The Environmental Impact of DDT DDT has a soil half-life from 22 days to 30 years. In aqueous systems, DDT either evaporates or is quickly absorbed by soil and organisms. DDT, DDE, and DDD are magnified through the food chain.

The RisksdWildlife • DDT is highly toxic to aquatic life (crayfish, daphnids, sea shrimp, many species of fish; it is less toxic to mammals, but cats are very susceptible (high death rate of cats in malaria control operations with an explosion in rat populations)) • Reproductive toxicantddecline of the bald eagle, brown pelican, peregrine falcon, and osprey • Eggshell thinning: birds of prey, waterfowl, and song birdsdless effect with chickens

The RisksdHuman • Direct genotoxityddeleterious action on a cell’s genetic material affecting its integrity • Indirect genotoxitydinduce enzymes that produce other genotoxic intermediates • Linked to diabetes • Developmental and reproductive toxicity • Xenoestrogenic activity (chemically similar enough to estrogens to trigger hormonal responses) • Amounts of DDT needed to control malaria might cause preterm birth DDT is linked to neurological problems, asthma, and cancer.

818

4. LIFE SCIENCE

DDT was less effective in tropical regions: continuous life cycle of mosquitoes and poor infrastructure. DDT was not pursued in sub-Saharan Africa due to these perceived difficulties. Spraying programs were ended due to concerns over safety and environmental effects, but mostly because the mosquitoes were becoming resistant to DDT.

The Irony Rachel Carlson’s work did not go without harsh criticism. The focus of the criticism is on the lives that could have been saved if DDT had not been banned. One such criticism was by author Roy W. Spencer: "While Carson is still admired for paving the way for future generations of environmentalists, governmental policies resulting from her work have caused the deaths of literally millions of people by allowing malaria to thrive in Africa. Instead of greatly reducing the amount of DDT that was so indiscriminately sprayed on crops, governments banned the use of the pesticide altogether. That the most famous policy reaction to environmental has caused so much human suffering should, by itself, make us wary of any sweeping efforts to ’protect the environment’" Roy W. Spencer, Climate Confusion p. 3. The mechanism of action in insects is that it opens sodium ion channels in the neurons, the neurons spontaneously fire, and the spontaneous firing leads to spasms and eventual death. The irony is that this is an example of evolution at work. Insects developed a resistance to DDT. The insects acquired the ability to metabolize the toxic DDT to noninsecticidal DDE.

4-20.0 The Anthropocene Period There is a timeline for the evolutionary history of life (https://en.m.wikipedia.org/wiki/ Timeline_of_the_evolutionary_history_of_life). About 3000 million years ago, cyanobacteria evolved, which initiated the creation of an oxygen atmosphere. Oxygen was a waste product that acted as a poison for many bacteria. About 1.85 billion years ago, eukaryotic cells appeared. About 530 million years ago, footprints appeared on land, indicating early animal explorations may have predated the development of terrestrial plants. Recognizable insects appeared 383 million years ago. The first shark appeared 350 million years ago, and the first dinosaur appeared 225 million years ago. The PermianeTriassic extinction event happened 251.4 million years ago in which 90%e95% of marine species were lost. The Tyrannosaurus rex appeared in the fossil record 68 million years ago. The CretaceousePaleogene extinction event happened 66 million years ago, in which half of all animal species were lost. Fossil records show that mammoths appeared 4.8 million years ago. Neanderthals appeared 350,000 years ago and became extinct 30,000 years ago. Modern humans appeared in Africa 250,000 years ago, and 50,000 years ago they began colonizing other countries. Geological time is marked in eons, which are subdivided into eras, eras into periods, periods into epochs, and epochs into ages. The divisions are defined by evidence found in the rock layers. The Pleistocene epoch was 800,000 years ago. This lasted until 10,000 years ago when the Holocene epoch started. This marked the end of the Late Glacial Period and also humans changing from hunteregatherers to domestication.

4-20.0 THE ANTHROPOCENE PERIOD

819

The Holocene epoch only lasted 10,000 years. In the year 2000, Paul Crutzen and Eugene Stoermer described the current time as the Anthropocene epoch. This marks the time when humans started to leave their biggest impact on the environment, and therefore on life. Future geologist will identify the Anthropocene epoch by the layers of garbage, in general, and plastic, in particular. The society has become a throw-away society. The 19th episode of the second season of the children’s television science series Beakman’s World was aired on November 26, 1994. The title "Garbage, Beakman, & Meteorology" underscores a main topicdgarbage. Garbage was used in a generic way to include things such as television sets and household chemicals as well as food. Two ways to get rid of garbage are discussed: landfills and incineration. Landfills create a problem because bacteria generate methane gas, which means a landfill can catch fire. As discussed in Chapter 5 ("Ecology"), the West Lake Landfill in St. Louis is currently on firedwhich creates a serious problem because West Lake Landfill also contains nuclear waste. If landfills are not properly sealed, the hazardous chemicals that are thrown away can migrate through the soil. The West Lake Landfill was, unfortunately, built in a floodplain area, which means the nuclear waste can find its way to underground water and streams. The second method of garbage disposal, incineration, also creates other problems. The burning of plastic gives off poisonous gas. Beakman and Lisa suggest the three R’s to reduce garbage: • reduce what we use • reuse what we use • recycle what we use Unfortunately, the three R’s are a thing of the past. In today’s world the manufacturers of goods cultivate a "throw-away" society to increase their profits. Mattresses may not be built to turn over because manufacturer’s want one to purchase a mattress every 5 years instead of every 10 years. Our society thus encourages proliferation of landfills, which is the signature of the Anthropocene epoch. And what does our society do with landfills that are filled? Landfills are covered with dirt, and houses and commercial buildings are built on defunct landfills. Landfills are part of our environment. Life is affected by the local environment. We are presently at the beginning of change, so change is not very noticeable to the majority. Some noticed a change in going from a global population of 3 billion to 7 billion. Will toxic materials of landfills reach into the foods-ball? What about the toxicity directly introduced into the environment by corporations that take advantage of reduced regulations? Sinclair Lewis wrote The Jungleda book that gives an account of the unregulated enterprise of the meat-packing industry. Will our nation’s water system be compromised? Will our air be polluted even beyond that envisioned by Lee Iacocca? In his book Our Final Century, Martin Rees, British cosmologist and Astronomer Royal, gives 100 years for mankind to determine its future. Just how thick will the Anthropocene layer be? In fact, will there be any life forms to even notice?

820

4. LIFE SCIENCE

4-21.0 Environmental Protection AgencydLooking After the Health of the People and the Environment Starting with the 1950s the general public was concerned about how human activity could have an effect on the environment and thus also on their health. Smog-chocked cities, contaminated rivers and lakes, pollution from emissions, industrial waste, raw sewage, and other sources were of great concern of Americans in the 1960s (The Week, April 21, 2017, p, 11). Even in the Seattle area in the 1960s, where almost everyone was an outdoor advocate who were active skiers and mountain climbers, haze prevented the 14,411-foot, snow-covered Mount Rainer from being seen even though it was only 50 miles away. Rachel Carson’s 1962 book Silent Spring drew attention to the indiscriminant use of pesticides, in particular DDT on the population of eagles. It was the general consensus of the population that the health and welfare of America were at risk. Richard Nixon signed an executive order that established the Environmental Protection Agency (EPA) that began operation on December 2, 1970. The mission of the EPA is to protect human health and the environment by ensuring that (https://www.epa.gov/about epa/our-mission-and-whatwe-do): 1) Americans were to have clean air, land, and water; 2) National efforts to reduce environmental risks to be based on the best available scientific information; 3) Federal laws protecting human health and the environment to be administered and enforced fairly, effectively, and as Congress intended; 4) Environmental stewardship is integral to US policies concerning natural resources, human health, economic growth, energy, transportation, agriculture, industry, and international trade, and these factors are similarly considered in establishing environmental policy; 5) All parts of societydcommunities; individuals; businesses; and state, local, and tribal governmentsdhave access to accurate information sufficient to effectively participate in managing human health and environmental risks; 6) Contaminated lands and toxic sites are cleaned up by potentially responsible parties and revitalized; and 7) Chemicals in the marketplace are reviewed for safety. To accomplish the EPA mission, the agency was to implement any environmental laws written by Congress. This was to be done by setting the national standards that states and tribes would enforce through their own regulations as well as the EPA regulations.

4-21.1 Why Save the Bald Eagle? The scientific name of the bald eagle is Haliaeetus leucocephalus, which comes from the Greek words hali (sea), aietos (eagle), leuco (white), and cepalos (head). The bald eagle is found only in North America, including all of the lower 48 states, most of Canada and Alaska, and the northern part of Mexico. The habitat of the bald eagle includes the seacoast, rivers, large lakes, and marshes. The diet of the bald eagle depends on the location. On the average the diet is about

4-21.0 ENVIRONMENTAL PROTECTION AGENCYdLOOKING AFTER THE HEALTH OF THE PEOPLE

821

56% fish, 28% birds, 14% mammals, and 2% other preys. In the Columbia River Estuary in Oregon, fish comprise about 90% of the diet: 58% live catch, 24% carcasses, and 18% pirated from other animals (USFWS, https). The bald eagle builds the largest nest of any North American bird; approximately 13 feet deep, 8 feet wide, and can weigh as much as a metric ton. The nests are built in large trees that are surrounded by water. In precolonial times, there were approximately 50,000 breeding pairs of bald eagles in the 48 contiguous states (USDA, 1978). When America adopted the bald eagle as its national symbol in 1782, there were as many as 100,000 nesting bald eagles in the 48 states and Alaska (AEF, httpsA). People perceived eagles to be a threat to livestock and the salmon population (AEF, httpsA). It was also believed that the eagles grabbed children with their talons (https://en. wikipedia.org/wiki/Bald_eagle). These misperceptions made the bald eagle an open target, and in the early 20th century, bounties were given for eagle carcasses (AEF, httpsA). The decline of the bald eagle compelled Congress to pass the Bald and Golden Eagle Protection Act of 1940, which prohibited the trapping and killing of birds. The catastrophic decline of the bald eagle after 1940 to a low of about 417 nesting pairs in the lower 48 states in 1963 was attributed to the use of pesticides, in particular DDT (AEF, httpsA). This led the United States to ban DDT in 1972 and Canada to ban DDT in 1973. The bald eagle was declared an endangered species in 1967. The bald eagle was protected by the Endangered Species Act of 1973. With regulations in place, and the use of hacking towers (artificial nests), the eagle population rebounded. According to the Fish and Wildlife Service (https://www.fws.gov/Midwest/eagle/population/chtofprs. html), the populations in breeding pairs of eagles over selected years (year, pairs) were (1963, 487), (1974, 791), (1981, 1188), (1990, 3035), (1991, 3399), (1992, 3749), (2005, 7066), and (2006, 9789). The bald eagle was placed on the Least Concern List on June 28, 2007.

Save the Bald Eagle Because it is the Canary in the Mine: Lead and Mercury Pollution The bald eagle is high in the food chain, as are humans. Whatever happens to the bald eagle in regard to habitat and diet can also happen to the human species (AEF, httpsB). The bald eagle is therefore the proverbial "canary in the mine"dto bring to our attention the introduction of toxic materials in the environment and the food chain. Since the bald eagle lives in all of the 48 contiguous states, the health of the bald eagle can identify local "hotspots" of mercury and lead pollution. Fish from streams, rivers, and lakes is a very large part of the diet of an eagle. Fish, shellfish, and aquatic birds are also a significant part of the human diet. Any methylmercury that is already in our body because of the widespread presence of the compound in the environment is only amplified by food that also has methylmercury. The symptoms of methylmercury poisoning on people of all ages include peripheral vision loss; "pins and needles" feelings in hands, feet, and mouth; uncoordinated movement; impaired speech and hearing; and muscle weakness. For children exposed to methylmercury in the womb, they may experience impacts to their cognitive thinking, memory, attention, language, motor and visual spatial skills. If metallic mercury is inhaled over prolonged periods, symptoms include tremors, emotional changes (mood swings and irritability), insomnia, neuromuscular changes, headaches, disturbances in sensations, changes in nerve responses, poor mental functions (https://www.epa.gov/mercury/health-effects-exposures-mercury). In 2009, 2 years after being placed on the Least Concern List in 2007, a study by the BioDiveristy Research Institute of Gorham, Maine (BRI, http), and the New York State Department of

822

4. LIFE SCIENCE

Environmental Conservation indicated high levels of mercury in one-out-of-four bald eagle chicks in the Catskills (Quinn, 2009). As reported by Quinn: "These findings are consistent with previous research showing the Catskills as a mercury ‘hot spot’ located downwind from mercury-producing plants in Ohio. These elevated areas of the Catskill and Shawangunks receive some of the highest rates of atmospheric deposition of mercury in the nation. Mercury becomes an air pollutant largely through releases from coal-fired power plants, solid waste incinerators and various smokestack industries. Airborne mercury eventually returns to earth in rain, snow, and fog droplets as well as in dry form." Quinn (2009). Rutkiewicz and coinvestigators reported studies on mercury levels in the brain, liver, breast, and primary feathers of bald eagles over the period 2002e10 in five Great Lake States: Iowa, Michigan, Minnesota, Ohio, and Wisconsin (Rutkiewicz, Nam, Cooley, Neumann, Padilla, Route, Strom, and Basu, 2011). They concluded: "These results suggest that bald eagles in the Great Lakes region are exposed to Hg at levels capable of causing subclinical neurological damage, and that when tissue burdens are related to proposed avian thresholds approximately 14e27% of eagles studied here may be at risk." Mierzykowski and coinvestigators (Mierzykowski, Todd, and Pokras, 2013) examined liver samples from bald eagle carcasses from Connecticut, Maine, Massachusetts, and New Hampshire for lead and mercury. They found that about 14% had lead levels high enough to indicate lead poisoning. Their concern was that lead and mercury were both long-lived in the environment; hence animals may suffer from chronic accumulation that would eventually affect their reproduction and subsequent survival. Jill Ettinger reported on the studies from the BioDiversity Research Institute (BDRI) on loons, falcons, and bald eagles in Maine (Ettinder, https). According to the BDRI report, bald eagles that make their homes near inland lakes are prone to higher mercury levels than average. This is because mercury in the air that is in by-products of industriesdsuch as metal production and the burning of coaldwill settle into the water. The fish ingest this mercury, which is then passed up the food chain. As noted by Ettinger: "Mercury emission levels from coal-fired power plants were recently regulated by the Environmental Protection Agency in the Mercury and Air Toxic Standard rule, but the heavy metal is still a high-risk contaminant in fish and seafood." DeSorbo and coinvestigators (DeSorbo, Burgess, Todd, Evers, Bodaly, Massey, Mierzykowski, Persico, Gray, Hanson, Meatley, and Regan, 2018) reported a study on mercury originating from the HoltraChem plant, a chlorealkali plant located on the banks of the Penobscot River in Orrington, Maine. They tested the effect of Hg concentration in nesting tissues: blood and breast feathers. The research involved four habitat types in the Penobscot River watershed (PRW): marine, estuarine, freshwater river, and lake. The most significant influence was the lake, and the least significant were the marine and estuarine. Although the levels of mercury were high in the impact zone near HoltraChem, the levels were nonetheless significantly lower than in the PRW and elsewhere in Maine not contaminated by HoltraChem. This was explained by the deposition of mercury that was carried by the atmosphere from elsewhere rather than

4-21.0 ENVIRONMENTAL PROTECTION AGENCYdLOOKING AFTER THE HEALTH OF THE PEOPLE

823

directly originating at the point source. What this means is that toxicity of any type is not localized to the point of origin.

Save the Bald Eagle Because It Is the National Symbol Many Native American Indians were deeply religious and communicated through symbols. Eagle feathers, claws, and wing bones (to make whistles and flutes) were used in religious ceremonies. The bald eagle was revered because of its wisdom, strength, boldness, and courage to withstand any obstacle. Francis Mitchell, a Navajo medicine man, said of the bald eagle: "The eagle was given the power from above. Whatever was before it, it would conquer and not back off." Landry (2014). The purpose of the eagle was to be the messenger that carried prayers to the Great Spirit because: "The eagle had the ability to live in the realm of the spirit, and yet remain connected and balanced within the realm of Earth." WP2PP, https. On July 4, 1776, the Continental Congress assigned to Benjamin Franklin, Thomas Jefferson, and John Adams the task to design an official seal for the new nation. The results were deemed unsatisfactory, as were the results of two subsequent committees. The three results were given to Charles Thomson, the secretary of Congress, to come up with something (Nix, 2015). In May 1782 the brother of a Philadelphian naturalist submitted a drawing in which the eagle was displayed as a symbol of power and authority. Congress liked the drawing, which eventually evolved to an eagle holding arrows in one talon and an olive branch in the other (ABEI, http). Congress adopted the bald eagle as the emblem of the United States of America. In this context, the bald eagle stood for unlimited freedom, sweeping through the valleys below or upward to the boundless spaces beyond (ABEI, http). The bald eagle is displayed on the Great Seal of the United States; is prominent on US stamps, coins, and currency; is part of the official seal of at least 17 branches and departments of the federal government; and is in art, music, etc. (Landry, 2014). The bald eagle is in a special place when it comes to saving endangered species. It would be embarrassing for the United States to have it as its national symbol, a species that became extinct because of human activities. It was the scientific knowledge of the toxic nature of DDT and the political cooperation of Congress that brought back the population of our national symbol.

4-21.2 The EPA and Crop Protection Toxic pollution is not limited to the effect of elements and pesticides on animal life. With the introduction of genetically modified organisms by mega industrial agricultural companies such as Monsanto, plant life and small farms are also threatened by toxic herbicides. One such herbicide is the weed killer called dicamba, which is produced by Monsanto, BASF, and Dupont. Eric Lipton reported on a meeting called by the EPA and attended by pesticide manufacturers, state agriculture officials, farmer groups, and environmentalists ("E.P.A. Says Drift of Herbicide Damaged Crops in 25 States," The New York Times, November 2, 2017). Damage complaints were

824

4. LIFE SCIENCE

compiled by plant science professor Kevin Bradley of the University of Missouri. The herbicide was applied to fields of genetically modified soybeans and cotton. But one cannot control Nature, and the wind blew the herbicide onto adjacent farms that were growing conventional crops. Damage was done to tomatoes, watermelons, cantaloupes, vineyards, pumpkins, organic vegetables, residential gardens, trees, and shrubs as well as soybeans. There were 2,708 complaints reported to state agricultural officials from 25 of the 34 states where "over-the-top" applications of dicamba were approved for use.

4-21.3 Government Regulation of Industry Is Cheaper Than Paying for Cleanups With Compensations Corporations exist only to make a profit. Decisions are made to minimize cost to maximize profits for stockholders and CEOs. In many cases, this means low wages and ignoring safety measures. A prime example is given in Sections 5-10.0e5-10.5 regarding the Deepwater Horizon Disaster. Landfills are also a major problem of large expense because of hazardous waste. The following are a few examples.

Hazardous Chemicals The Love Canal was a project gone wrong. Originally planned in 1892 as a shipping lane to bypass Niagara Falls, the project was abandoned when financial backing failed because of the financial panic of 1893 and Congress passing a law barring removal of water from the Niagara River to preserve the Falls. The partially dug canal became a dump site in the 1920s for the City of Niagara Falls. In the 1940s, Hooker Chemical Company was looking for a dump site for caustics, alkalines, fatty acids, and chlorinated hydrocarbons from the manufacturing of dyes, perfumes, solvents for rubber, and synthetic resins. The site was cover with a clay seal to prevent leakage. Eventually the Niagara School Board took over the land and proceeded to develop it. In 1976, toxic chemicals were found in sump pumps near Love Canal. After a year, Michael Brown, a scientist, investigated health effects of the Love Canal incident. Brown reported incidents of birth defects and other defects due to the leakage of the toxic chemicals. Many of the homes were built atop buried chemical waste pockets. This activated the Homes Association. The government stepped in, and Love Canal became a Superfund site. In 2004, federal officials announced the superfund cleanup has ended. The cost was $400 million dollars, and 950 families had been evacuated. A report in 2013 indicated that toxic waste was still oozing from this Supersite (https://nypost.com/2013/11/02/love-canal-still-oozing-poison-35-years-later/).

Toxic Mercury Mallinckrodt Chemical Company of St. Louis is the last holder of the HoltraChem in Orrington, Maine. Approximately 6,000 tons of mercury-contaminated soil was hauled away from the premises as of February 2016 (Gagnon, 2016). In the article, environmental specialist for the Department of Environmental Protection said: "They’re actually in the process of trying to define the extent of the contamination. It’s open ended at this point, and it’s primarily because each area seems to be wider and more in area than what was originally expected." This should be no surprise because chemicals do not stay in one place, even when under ground.

4-22.0 "MAKE AMERICA TOXIC AGAIN"

825

Radioactive Waste Mallinckrodt is also associated with the nuclear waste problems in the St. Louis region. Mallinckrodt Chemical Company was chosen to provide purified uranium for the Manhattan Project to develop the atomic bomb in the 1940s and continued to produce purified uranium for the next 20 years (see Sections 5-8.5e5-8.12). The cleanup of nuclear waste sites throughout the United States and worker compensations cost tens of billions of dollars. The West Lake Landfill site has not yet been completely cleaned up partly due to an underground fire.

4-22.0 "Make America Toxic Again" "I’ve never known any administrator to go into office with such an apparent disregard for the agency mission definition or science." Christine Todd Whitman, former New Jersey Governor and Administrator of the Environmental Protection Agency EPA under President George W. Bush (Leber, 2018, p. 30). The title of this subsection was taken from the cover of the March + April 2018 issue of Mother Jones. On the cover is an image of the White House with an "industrial roof" of chemical storage tanks and five smoke stacks billowing heavy black smoke and one with a methane flame of fire. At an open window is Trump, the 45th President of the United States, identified as "No45" for brevity in the following discourse. The cover is the signboard to an article by Rebecca Leber about Scott Pruitt, whom Leber called the "Toxic Avenger" (Leber, 2018). Scott Pruitt’s hometown is Broken Arrow, Oklahoma. Located 15 miles southeast of Tulsa, the town is named for Native American Indians who were forcibly relocated in 1836 during the "Trail of Tears" expulsion organized by President Andrew Jackson. Broken Arrow is a town of 107,000 residents with a median income 43% higher than the rest of the state because of the dominance of the oil industry. Broken Arrow also has a high evangelical population (see Section SS-15.7 for the four premises of Evangelical Christianity). One of the many evangelical mega churches is the First Baptist Church of Broken Arrow. On its website is the proclamation of their mission: ".to reach everyone that we can with the Gospel of Jesus Christ in Broken Arrow, Tulsa, Oklahoma, North America and the Ends of the Earth." If this sounds familiar, it is because these goals are similar to those stated in the Wedge Document that was the driving dictum of the Intelligent Design movement discussed in Section SS-15.23 ("Our Government Has Been Wedgied"). According to Leber: "Pruitt’s two guiding stars - evangelical faith and political zeal - sometimes seem interchangeable." Leber (2018, p. 26). In the table "Emissions Accomplished" on page 25, Leber lists 16 areas subjected to Pruitt’s systematic attack on environmental protections. Explicit mention is made of lead and/or mercury in the categories Hazardous Air Toxic and Power Plant Pollution. The category Dangerous Pesticides speaks for itself as to what regulations are to be reduced. Implicit in the relaxation of regulations on chemicals that affect the bald eagle are Clean Water Protection, Oil and Gas Drilling, Coal Ash, Abandoning Enforcement, Stacking the Agency With Industrial Allies, and Slashing Staff and Hiring Cronies.

826

4. LIFE SCIENCE

In addition to the mission of Pruitt to reduce the effectiveness of the EPA, No45 wants to exacerbate the toxic situation by increasing the number of coal-burning power plants and the repeal of Obama’s Clean Power Plan, the first-ever plan to curb carbon pollution from US power plants.

4-22.1 Basis of Toxicity Positions In regard to the three-legged stool of society, science has been attacked by religion and politics in the past; hence the present attack on science is wrapped in history. What are important to record are the reasons for these confrontations. During the 1500s and early 1600s, it was a question of authority of the Catholic Church versus the Sun-centered Universe of Copernicus and Galileo. In Nazi Germany, it was the "Jewish science" versus political ideology. In the United States (see Section SS-14.3, "The Third Face of Eve: The Period of Babel (2016 to ???)"), it is environmental science versus an alliance of religious and political extremists in powerful political positions. To simplify the discussion without too much loss of content, the focus is on the two most powerful political leaders in this contemporary War on Science, Scott Pruitt, the (current) Director of the EPA, and his boss, No45.

Scott Pruitt The guiding light for Scott Pruitt is the religious beliefs of far-right Evangelical Christians. One of the four premises of Evangelical Christianity is obedience to the Bible as the Ultimate authority (see Section SS-15.7, "A New Political Base in American Society"). This in itself is not the major reason Pruitt is antiscience, since obedience to the Bible runs through all forms of Christian worship. The Bible being an Ultimate authority is likewise part of all Christianity. There are two important points that distinguish evangelicals from other Christian denominations: extent of authority and the interpretation of passages. As to the extent of authority, one need only revive the quotation of Galileo: "The Bible shows the way to go to heaven, not the way the heavens go." Nowhere in Genesis 1 is there a description of how God made everything in the Universe; only that everything was good. Mainstream Christianity accepts the findings of science when it comes to explaining how Nature works. For the evangelicals the Bible verse of "authority" on the relationship of humans and Nature is Genesis 2:15. There are many versions of Genesis 2:15, of which three are now compared. Leber quoted Nick Garland, senior pastor of the First Baptist Church of Broken Arrow: "The Lord God took the man and put him in the Garden of Eden to work it and take care of it." Nick Garland (Leber, 2018, p. 26)dNew International Version. Two other popular versions include the following:  en to dress it and to keep it." • "And the Lord God took the man, and put him into the garden of E’d King James Version • "The Lord God placed the man in the Garden of Eden to tend and watch over it." New Living Translation

The major differences in these three versions are found in the phrases: work it and take care of it; dress it and to keep it; and tend and watch over it. How are these words to be interpreted in terms of

4-22.0 "MAKE AMERICA TOXIC AGAIN"

827

the duty of man given by God? In his commentary on Genesis 2:15, Ritenbaugh gives the following interpretation: "God has given man powers to carry out the responsibility that has been given into his hands: to have dominion. Man must do the following: Put what has been placed into his hands through a finishing process, watch over it, guard it, protect it, and preserve its beauty." John W. Ritenbaugh, Bibletools, https://www.bibletools.org/index.cfm/fuseaction/ Bible.show/sVerseID/46/eVerseID/465. This interpretation is in contrast to what Nick Garland said about Genesis 2:15 as relayed by Leber: "Failing to use the Earth for our benefit, he notes, would violate Genesis 2:15, which concerns the relationship between humans and the natural world." Leber (2018, p. 26). Note the difference in regard to the allegiances. In Ritenbaugh’s interpretation the alliance is "between God and man" in which man is to guard, protect, and preserve what God created. In Garland’s interpretation the alliance is "between humans and the natural world" in which man is to use the Earth for our benefit without any concern in preserving that which God created. What about God and the eagle? This is what Genesis says about the birds in the sky: "And God said, Let the waters bring forth abundantly the moving creature that have life, and fowl that may fly above the earth in the open firmament of the heaven." Genesis 2:20, The King James Version. Does not "fly above the earth in the open firmament of the heaven" describe the eagle? Did not God consider this to be good? It is somewhat ironic that Nick Garland compared the ambitions of Pruitt to the eagle: "Eagles are one of the rare creations of God that delight in the storm." Leber (2018, p. 26). The analogy is that Pruitt has been fighting the EPA for years. The irony resides in the "inspired" efforts of Pruitt to reduce the protection efforts of the EPA. Do not the restrictions, regulations, and inspections by the EPA protect what God considered to be good in this scenario, i.e., the bald eagle? Mercury unleashed to the environment under a greatly crippled EPA can only lead to an increase in mercury poisoning of the bald eagle, with the real potential to become extinct.

No45 The understanding of science by No45 is best given by his views on physical exercise. Although No45 participated in sports in his youth, he believes exercise leads to an early death (Cillizza, 2017; Rettner, 2017). Why is this? No45 believes the human body is like a battery with a finite amount of energy. Hence, exercising uses up energy, and when the energy is depleted the body dies. His two main forms of exercise are playing golf (he rides in a golf cart) and standing and rallies on the campaign trail (Cillizza, 2017).

828

4. LIFE SCIENCE

The analogy of a battery being associated with the finite energy of the body is a good one because it reveals two things about No45: a lack of understanding of how a battery can be recharged and why foods are categorized into food groups. Anyone who has attended kindergarten in public schools was taught the five food groups (for kids) that provide nourishment: grains, vegetables, fruits, milk/dairy, meat/beans (https:// pediasure.com/child-development-nutrition/5-food-groups-kids). The nutrients provided by food groups are carbohydrates, proteins, fats, minerals, vitamins, fiber, and water. Any rechargeable battery could be used in the following discussion, such as the battery of a laptop computer. However, the automobile is a good metaphor for how the human body works and the importance of exercise. If an automobile sits in place for a very long time, the battery runs down. A symptom of this condition is that there is not enough energy in the battery to start the engine of the car. The battery must therefore be recharged by hooking it up to a recharger device to reverse the chemical reaction and thus establish a potential difference between the poles of the battery. A moving automobile provides a relationship between a battery and the nutrition in food groups. The battery of the car only provides the spark to start the engine. Once the car is in motion, the source of energy is the gasoline. While in motion, the alternator converts mechanical energy into electrical energy, which is used to maintain the charge of the battery. When one exercises, the energy burned up by the muscles (the spark) is replaced by the nutrients stored in the body (the gasoline). Just as one goes to the gas station to refill the tank with gasoline, one goes to the farmers market to refill the store of energy used up by the body. This process of replenishing the "gas tank" is referred to as eating. Gasoline comes in different octane numbers, which denote different qualities of performance in regard to engine knocking. Similarly, foods have different nutritional values. A Big Mac at McDonalds has a low nutritional value and was brought out in the documentary movie Super Size Me. Anyone who routinely eats Big Macs is likely to be overweight. Not knowing that batteries can be recharged and why eating nutritious food is necessary means that No45 has no understanding of the chemistry and physics of the real world. Facts regarding the environment are therefore meaningless in making decisions. But this is no surprise because similar examples of "impulse buying" can be found in other areas of politics. On impulse, No45 started a trade war by increasing tariffs on steel and aluminum. After some flack from Canada and Mexico, those countries were declared exempt from the tariff. Many economists were appalled at this move by No45. Gary Cohn, chief economic advisor, who planned to host a meeting where executives could tell No45 how the proposed tariffs could harm their businesses, resigned when his views were dismissed. Tariff laws in the 1930s are said to have exacerbated the Great Depression. Similarly, the proposed tariffs on steel and aluminum will raise prices of items made from aluminum and steel in an already depressed society. The shootings at Marjory Stoneman Douglas High School in Parkland, Florida, on February 14, 2018, left 17 dead. This incident mobilized the Parkland students to lobby the government on gun control and mobilized students in other states to do likewise. The response of No45 was to endorse restrictions on gun sales, such as more powerful background checks, and to propose bonuses for teachers who get gun training. The premise of the latter was that no one would enter a school if they thought they might be killed. Apparently not taken into consideration was that a faculty member with gun training and carrying a concealed weapon may likewise not want to take the chance of being killed by someone with an AR-15. Also ignored were real data. Georgia students challenged this proposal by citing an incident in which a teacher, who was well-liked,

4-22.0 "MAKE AMERICA TOXIC AGAIN"

829

fired a gun at school (http://www.latimes.com/nation/la-na-teacher-shooting-20180228-story. html). (Meetings of faculty with administrators might be more interesting, however.) The youth-led movement made its impact: from Dick’s Sporting Goods to Delta Airlines, major corporations turned against the National Rifle Association (NRA), and Florida enacted its first gun violence prevention law in 20+ years. Even though there were inflammatory twitters between No45 and Kim Jong Un, leader of North Korea, No45 accepted the invitation of the North Korean leader for a meeting. This stunning announcement set diplomats and the White House staff scrambling to react, and the World viewed No45 as acting as his own diplomat, negotiator, and strategist. Again, no input was sought from the learned advisors. What do all of the examples say about the motivations and actions of No45? Nothing that could not have been anticipated by the "20 Items" listed in Section SS-15.0: the lack of respect for people (Item 1), seeking credit for what he did (Item 2), and being paranoid (Item 5) when it comes to advisors; the gut responses to situations (Item 8), not interested in academic topics (Item16); and distortion of information (Item 19). In other words, No45 is self motivated.

4-22.2 Toxicity and Disrespect of the National Symbols: A Political Football "The national seal and the American flag are the only two symbols created by law. As such, eagles are protected by additional federal laws. Eagles are protected under law. That extends beyond killing them. You can’t shoot at them or molest them or disturb them. You can’t even disturb an eagle’s nest. If you disturb a nest, that’s a violation of law." Steve Oberholtzer, special agent in charge for the US Fish and Wildlife Service (Landry, 2014). The date is October 23, 2017. At the top of an electric billboard on permanent display is an image of the profile of President Lincoln, who was raised in a poor household. To the right of the Lincoln profile are the words "Lincoln Financial Field," which is the name of the stadium. It is the Monday Night Football game between the Philadelphia Eagles and the Washington Redskins. A huge American flag is on the field, parallel to the ground, held by several servicemen. The National Anthem begins. No football player is kneeling, a signal to draw awareness of injustice in our country; but a few have their right hand lifted in the manner of Tommie Smith in the 1968 Olympics in Mexico City. Some football players and fans in the stands did not place their right hand over their heart. As the words ".land of the free." were sung, a bald eagle was released and flew around the stadium to a cheering crowd (https://www.youtube.com/watch? v¼Ss4rOnzq-pO). The eagle’s name is Challenger (Drake, 2018) and has been flying around football and baseball stadiums for years during the playing of the National Anthem.

Disrespect for the National Symbol: The American Flag (According to No45) The biggest sports story of 2017 was initiated by Colin Kaepernick when, upon advice of NFL player and Army veteran Nate Boyer, he knelt during the playing of the National Anthem to protest racial inequality and police brutality, and to show respect for those who were killed by unjustified shootings. Players on other teams followed suit. As noted by Eric Reid of the San Francisco 49ers, they chose to kneel because it was a gesture of respect. But No45 turned these solemn incidents of respect into displays of disrespect for the American flag, as unveiled in the subsections of Section SS-15.22 ("What Makes America Great: The Freedom to Protest"). The titles of the subsections are Protests: The NFL, the "Star-Spangled Banner," and the First Amendment; and

830

4. LIFE SCIENCE

Protests: Protesting the NFL ProtestersdWhite House Style. These subsections, as well as the subsection The National Anthem and Sports should be reviewed before continuing with the present discourse, especially the part on behavior during the playing of the National Anthem in which the word "should" is used. [To the Reader: The comedian Steve Wright wonders if his mother sees the irony when she calls him a son-of-a-bitch. There are two ironic overtones to the kneeling incidents by the football players. In the spirit of the observation made by Wright, is the irony recognized by the general public when No45 literally commanded all football players to stand when a song about the "land of the free" is being played in sports stadiums? There is a difference between sports events being associated with politics and a sports event that becomes a political event. When kneeling as a sign of respect was turned into a sign of disrespect for the flag by No45, sports events became political events. That conversion being made, there is a bit of irony to say that a political statement of protest is unpatriotic when given at a political event.]

Disrespect for the National Symbol: The Bald Eagle "In an eagle there is all the wisdom in the world. If you are planning to kill an eagle, the minute you think of that he knows it, knows what you are planning." Lame Deer, Sioux Medicine Man (Landry, 2014). As brought out in Section 4-21.1, even with EPA oversight and enforcement of regulations, the toxic elements lead and mercury are greatly affecting the bald eagle population. By greatly crippling the EPA through budget cuts, replacing scientists with industrial personnel on review boards and panels, and lessening restrictions and regulations, the outcome can only result in an increase in lead and mercury pollution. What this means is that the policies of Pruitt and No45 once again place the bald eagle on the road to the endangered species category and, inevitably, to the graveyards of the bald eagle. This result is as obvious as the deflation of an automobile tire once the pressure valve is released.

Doritos, The Flag, and the Eagle "Crunch all you want. We’ll make more." Jay Leno, Doritos Tortilla Chips Commercial, 1990. The Doritos Tortilla Chip commercial is meant to encourage people to eat Doritos. There are many versions of their commercials, but not all contain the above quotation about making more. In spite of these commercials, one can still find Doritos on the shelves in stores. The American flag is made of fabric sewn together to show thirteen stripes of red alternating with white, with a blue rectangle in the canton bearing 50 small, white five-pointed stars. If all of the American flags in the United States were to simultaneously disappear, there should be no worry. China can make more. The bald eagle is native only in North America. If all of the bald eagles were to simultaneously disappear in North America, no more can be made. Think of the embarrassment to the United States if pollution was left to run rampant without government restrictions and inspections on

REFERENCES

831

pollutants that affect the population of eagles. Would all of the symbols of the bald eagle on government seals, coins, and documents have to be corrected by placing an "X" across each eye to indicate the bald eagle was extinct? Benjamin Franklin wished that the bald eagle were not chosen to represent the United States. A partial list of the reasons why Franklin held this view of the bald eagle is as follows: ".he is a bird of bad character, he does not get his living honestly, .too lazy to fish for himself, he watches the labor of the fishing-hawk, and when that diligent bird has at length taken a fish, and is bearing it to its nest for the support of his mate and young ones, the bald eagle pursues him and takes it from him." Benjamin Franklin (ABEI, http). Does this description sound familiar? Was Franklin ahead of his time?

References ABEI, http, "Bald Eagle, US National Emblem", American Bald Eagle Information. http://www.baldeagleinfo.com/ eagle9.html. AEF, httpsA, "Decline & Recovery", American Eagle Foundation. https:www.eagles.org/what-we-do/educate/learnabout-eagles/bald-eagle-decline-recovery/. AEF, httpsB, "Dangers Facing Bald Eagles", American Eagle Foundation. https:www.eagles.org/what-we-do/ educate/learn-about-eagles/bald-eagles-current-dangers/. BRI, http, "Raptors: Contaminant Monitoring/Mercury in New York State Bald Eagles", Biodiversity Research Institute. http://www.briloon.org/mercury-in-new-york-state-bald-eagles. Cillizza, C., May 15, 2017, "Donald Trump has a very strange theory about exercise", CNN. https://www.cnn.com/ 2017/05/15/politics/Donald-trump-exerciose/index.html. DeSorbo, C.R., Burgess, N.M., Todd, C.S., Evers, D.C., Bodaly, R.A., Massey, B.H., Mierzykowski, S.E., Persico, C.P., Gray, R.B., Hanson, W.E., Meatley, D.E., Regan, K.J., June 15, 2018, "Mercury concentrations in bald eagles across an impacted watershed in Maine, USA", Science of the Total Environment, vol. 627, pp, 1515e1527. https://www. sciencedirect.com/science/article/pii/SOO48969718300238. Drake, S., 2018, "Meet Challenger, a bald eagle whose soaring skills are in high demand", Washington Post. https:// www.washingtonpost.com/news/animalia/wp/2018/01/12/meet-challenger-a-bald-eagle-whose-soaringskills-are-in-high-demand/?utm_term¼.96e66dbf1a3a. Ettinger, J., https, "Could Bald Eagles Decrease Mercury Poisoning?", Naturally Savvy. https://naturallysavvy.com/ care/could-bald-eagles-decrease-mercury-poisoning. Gagnon, D., February 3, 2016, "6,000 tons of mercury-contaminated soil hauled from HoltraChem", Bangor Daily News. http://bangordailynews.com/2016/02/03/news/Penobscot/6000-tons-of-mercury-contaminated-soilhauled-from-holtrachem). Kornberg, R.D., May 1974. "Chromatin structure: a repeating unit of histones and DNA", Science 184 (4139), 868e871. Landry, A., June 20, 2014, "Native History: Sacred Bald Eagle Becomes U. S. National Emblem", Indian Country Media Network. https://indiancountrymedianetwork.com/history/events/native-history-scred-bald-eagle-becomesus-national-emblem/. Leber, R., 2018, "Toxic Avenger", March + April issue of Mother Jones, pp. 22e31. Madigan, M., Marrs, B., April 1997. "Extremophiles", Scientific American 82e87. Mierzykowski, S., Todd, C., Pokras, M, May 24, 2013, "Why do our bald eagles have high levels of lead, mercury?", U. S. Fish and Wildlife Service Northeast Region. https://usfwsnorhteast.wordpress.com/2013/05/24/why-do-ourbald-eagles-have-high-levels-of-lead-mercury/. Mierzykowski, S., Todd, C., Pokras, M., Oliveira, R., April 2013, "Lead and Mercury Levels in Livers of Bald Eagles Recovered in New England", U. S. Fish and Wildlife Service Maine Field Office. https://fws.gov/northeast/ mainecontaminants/pdf/PbHg_BAEA_LiversNewEngland2013.pdf. Nix, E., February 25, 2015, "How did the bald eagle become America’s national bird", History. http://www.history. com/news/ask-history/how-did-the-bald-eagle-become-americas-national-bird.

832

4. LIFE SCIENCE

Olins, A.L., Olins, D.E., January 1974. "Spheroid chromatin units (n bodies)", Science 183 (4122), 330e332. Pierre-Louis, K., 2018. "What Cameras on Polar Bears Show Us; It’s Tough Out There", The New York Times. https://www. nytimes.com/2018/02/01/climate/polar-bear-cameras.html?emc¼edit_tnt_20180201&nlid¼15851982&tntemail0¼y. Quinn, E., January 1, 2009, "Icon threatened: new study finds bald eagles have high level of mercury", New Paltz Times. http://www.briloon.org/uploads/BRI_Documents/Raptors/EaglesMercuryNewPaltzTimes1Jan09.pdf. Rettner, R., May 14, 2017, "Trump thinks that exercising too much uses up the body’s ’finite’ energy", The Washington Post. https://www.washingtonpost.com/national/health-science/trump-thinks-that-exercisin-too-much-usesup-the-bodys-finite-energy/2017/05/12/bbOb9bda-365d-11e7-b4ee-434b6d506b37_story.html?utm_term¼. 221a22fe19d6. Rutkiewicz, J., Nam, D.H., Cooley, T., Neumann, K., Padilla, I.B., Route, W.m Strom, S., Basu, N., 2011, "Mercury exposure and neuochemical impacts in bald eagles across several Great Lakes states", NCBI Resources. https:// www.ncbi.nlm.nih.gov/pubmed/21735125. USDA, 1978, "Threatened and Endangered Species: Bald Eagle Fact Sheet", USDA Natural Resources Conservation Service - Montana. https://www.nrce.usda.gov/wps/portal/nrcs/detail/mt/home/?cid¼nrcs144p2_057911. USFWS, https, "Bald & Golden Eagle Information", U. S. Fish & Wildlife Service. hppts://www.fws.gov/birds/ management/managed-species/bald-and-goplden-eagle-information.php. Van Holde, K., Sahasrabuddhe, C.G.I., Ramsay-Shaw, B., 1974. "A model for particular structure in chromatin", Nucleic Acids Research 1 (11), 1579e1586. WP2PP, https, "Eagle Symbol". https://www.warpaths2peacepipes.com/native-american-symbols/eagle-symbol. htm.