Information and uncertainty in living systems, a view from ecology

BioSystems

ELSEVIER

Information

and uncertainty

38 (1996) 141-146

in living systems, a view from ecology Ramon Margalef

University of Barcelona, Barcelona, Spain

Abstract The organization of living entities combines, in close proximity and partial overlap, dissipative and self-organizing systems. Their superposition, in which gradients of opposite signification cross, allows local discontinuities to occur, and in them a place for marginal chaos and fractal configurations. Among other features, a difference in turnover speed characterizes such coupling, higher on the relatively more uniform domain where entropy increases more easily, and lower at the more minutely organized places of preferential information accretion. At the level of elementary physical events, logical aspects of indeterminacy could perhaps be clarified by an observer, assuming that the living system performs the role of a witness of historical progress. Keywords:

Dissipative system; Ecology; Indeterminacy;

1. Integrated organizative

systems:

dissipative

and

self-

Living systems, from cell organelles, to organisms or to ecosystems, are open dissipative systems, in the sense of Prigogine (196 1). There is no doubt about that. The comparison of a forest with a system of Binard cells will be always inspiring to the ecologist. Living systems, as dissipative systems, take the form of ‘holes’ opened across a gradient, through which power can be extracted and made to perform work. A dissipative system that lasts is out of equilibrium, and any system out of equilibrium is potentially dissipative. Living systems also have self-organizational or autopoietic properties. In them, information is stored and accreted as part of a growing organization (miniaturized structures apt to act as ma* Corresponding author. 0 1996 Elsevier Science Ireland 0303-X47/96/$15.00 SSDI 0303-2647(95)01584-8

Information;

Self-organization

chines) or as specific and particularized memories. The local increase of organization is paid for by an equivalent and measurable increase of entropy somewhere else. In this sense, Schriidinger (1944) wrote about organisms feeding on negative entropy. This is a creative outlook, although the way it has exercised its seductive power over biologists and ecologists has been often and rightly been criticized by rigorous thermodynamicists (Pauling, 1987; Mansson and McGlade, 1993). Actually, the relations between life and entropy have a long history of misunderstandings. Organisms have often been compared to mechano-chemical machines; at present, their aspects related to cybernetics and information attract more attention; indeed, these two views are complementary. Fundamentally, biological and ecological systems are physical systems. Therefore, ecology should be more open that it seems to be prepared, to assimilate the concepts of force and

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acceleration, as well as variational principles the comments of Murray, 1992, and Quenette Gerard, 1993).

(see and

2. Materialization of relevant structures in biology and ecology The body of each organism - and tentatively also each ecosystem - is also a frame supporting crossed gradients of entropy ‘production’ and of information gathering. Such gradients are not necessarily straight and continuous, but convoluted in relation to the complexities of the organization. Actually, gradients and frontiers appear as places for the edge of chaos to manifest itself. Entropies are additive, but information is multiplicative. The value, in terms of information, of one bit added to a system usually depends on the previous size of the system. This generates size dependence and time asymmetry, unavoidable and effective in life and in evolution. Dissipation of energy and self-organization appear as necessary functions in all associated structures that have developed and remain in continuity, but tend to differentiate. The trophic, dissipative part, predominates in the primary producers of ecosystems and in the digestive systems of animals; the self-organizing part is prevalent in the consumers and still more in their brains. Topological relations in the detailed configuration and overlapping of all these gradients are components of organization. Like gradients and boundaries between fluids that differ in physical properties, they are sites of choice for the manifestation of interface phenomena. More or less regular bulges and heterogeneities generate discontinuous exchanges that may suggest an edge of chaos pattern, occurring mostly through fractal surfaces. Less active biomass or necromass (wood), as well as exosomatic contraptions (Margalef, 1991), including synthetic molecules and entities qualifying as robots (‘second order organisms’) etc., may be materially and are functionally contained between layers of the real or virtual interfaces, being fed by exosomatic energies and delivering eventual benefits to their ‘master organisms’.

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Turnover rates and associated properties follow the gradients, justifying what I wrote several years ago (Margalef, 1968) about the possibility that always ‘the less mature ecosystem feeds the more mature structures around it’, or that the parts with a more rapid and dissipative turnover support the parts that turn over slowly, where information accumulates faster. The substance of this view may be more easily accepted in a tacit way than recognized expressly (Matsuno, 1978, 1984). Its validity extends from cells from metabolic cycles to nucleic acids - to ecosystems - and in them from photosynthetic organisms to big predators - and beyond, applying also to our Earth and the rest of the solar system. The additive nature of entropy and the multiplicative properties of information are conductive to the persistence of such a creative dynamics. In all living systems, the historical results of natural selection could be quantitatively and tentatively expressed with reference to the product of the energy flow times any convenient measure of the information content (E.1). The time derivative of this, E(dZ/&) + I(&/&), might suggest the possibility of a variational principle that could describe the regular evolution of the system, as concerns energy flow and information (organization). This formula has proved useful for reducing to its bare bones the expression of the dynamics of plankton (Margalef, 1991): dissipated energy is equated to turbulent energy in the environment, and information is substituted by the degree of covariance in the distributions of the reactants. Since photons are not displaced by turbulence, light has to be considered as one of the reactants. In this application to plankton, ecological succession is characterized by the decay of turbulent energy and a growing segregation of potential reactants. 3. Variational principles and information Ecology has benefited from statistics for comparing observations among them, or with the anticipations provided by theories being tested. An effective appreciation of changes may require consideration of forces and accelerations. There is

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always hope of discovering variational principles which will apply to ecology. Volterra (1937) dared to propose a principle of minimal action that continues to be a stimulus, if not, regrettably, an effective source of inspiration. His function of ‘vital action’,

c Jo s

a=-

(C ai Ni log Ni) dt, j=l

has been unjustifiably forgotten Many of these and other aspects are peripheral to the desire to make views on the historical development of living entities compatible with sound physical principles. The development of organisms and ecosystems starts with tentative and generally not very efficient use of available energy and materials. Organization develops fast, then continues later in what seems to be a more parsimonious way. Equivalent approaches could be extended to include the cultural evolution of new synthetic molecules and of inanimate artifacts, when these are introduced in the biospheric processes. In such artifacts (some of which may qualify as second order organisms) the ‘recovering’ of spent energy as information continues to be evident. Consider gasoline being fed to the motor of a car and the way the abrasion of the moving parts is recorded in the small changes on the surfaces of the different parts of the mechanism. This appears to be pasive, but otherwise is equivalent to some forms taken by the acquisition of information by living organisms. A more significant path in the acquisition of information occurs through the natural selection exerted by consumers on the different models of cars. A topological imperative leads to a singularity and the disjunction of the different centers of accretion of information. It determines that each ‘individual’ tends to be isolated from other organizing centers, with the result that all appear disjoined and dispersed inside a less organized and continuous matrix, where entropy tends to increase generally and where the processes of selforganization are relatively harder to identify. So a basic feature of nature is generated: stars in the Iirmament, towns in the landscape, plankton in water, trees and animals in the jungle and, in general, individuals dispersed in an environment. Self-

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organization always is nucleated around points dispersed in a less organized substrate that provides opportunities for increasing differentiation in and around the established centers. Natural selection works at all the levels of replicating entities. In our species, the transmission of ‘cultural’ information is exceeding, by its speed, the standard transmission of information recorded in the genetic system and its eventual increase through natural selection. Thus, new possibilities appear, and exosomatic contraptions - from tools and instruments to highways and towns - and new kinds of molecules and informatic nets, join in the evolution of the artificial, fed by exosomatic energy, most of it derived now from fossil fuels and supplemented by nuclear fission. This goes along with a tremendous increase in the amount of ‘exported entropy’ associated with development. Consideration of the properties of information suggests some rules that may be significant in evolution. One ‘unit’ of information may be more effective when it is a part of a large system, since real information contents are proportional to a power or to the logarithm of the size of their respective stores. This represents a bonus for large size systems, from individuals to ecosystems, caught in a frame where natural selection of quasi replicable entities is a dominant mechanism. The development of strategies is equivalent to the exploratory expansion of information systems 4. Energy in the biosphere Events and their material substrates in the biosphere are very complicated and it is almost impossible to declare energy lost or a piece of information obsolete. The ways of several groups of dominant organisms, unrelated among themselves through evolutionary or genetic affinities, tell us a very instructive history. Such organisms are apt to amplify their effectiveness as dissipative systems - mobilizing lots of energy and have a capacity for using the extra power to outdistance potential competitors. Stromatolites, trees (forests, including fungi), corals, eusocial insects and mankind, as five distinguished and

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notably successful - according to human standards - peaks in evolution, are not genetically related to each other, but all have in common the capacity to exert an important control over the surrounding (exosomatic) energies and space. Ecology traditionally took into account only the endosomatic forms of energy derived from primary production. This very concept is a proof of such a view, in the way that it contemplates photosynthesis and the food ingested and digested by other trophic levels, and through another familiar concept, the food web. Ecologists who wanted to be fairer to physics, and had a feeling for other aggregate forms of energy that are significant in supporting life (like H.T. Odum and a few others), soon discovered that the enterprise is difficult and scarcely appreciated by many colleagues (Mansson and McGlade, 1993). In the case of the organisms listed before, as well as probably in many others, it turns out to be extremely difficult to compute all the energies involved and consumed in some complex process. A more realistic point of view (Jegensen, 1992) would lead us to assigning separate efficiencies and corresponding rates of energy ‘losses’ - to each kind of energy involved (be it photons, chemical bonds, evapotranspiration, fossil fuels, even fission and fusion) and then to consider global efficiencies of the whole ‘machinery’ in a way that is customary in engineering practice. This program encounters, of course, considerable difficulties, and it is regrettable to recognize how neglected the various ways and paths of energy have been in ecology until now. And it may be a characteristic of the times that the recognition of the multiple and complex paths of the energy in ecosystems might lead ecologists only to distinguish ‘as engineers’ the organisms in which such modes are obvious (Jones, Lawton and Scachak, 1994). 5. Is life testifying to events at the lowest level? All the preceding may be useful as a preamble to an abridged discussion of another interesting aspect of our biosphere, related to indeterminacy in physics. Science is a product of self-organizing systems and may have survival value by itself or be

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associated with qualities that increase the probability of survival of the species. The basics of physical science is not my turf, but like any scientist, I keep wondering about the apparently counter intuitive notions in modem physics and also about how convenient it might be to grasp their possible meaning, when trying to develop the sciences of which physics is the foundation. I am not prepared to properly understand and follow all the arguments that are tossed around, and even less prepared to express any opinion on the philosophical interpretation of the whole history. I gather only that elementary events are difficult to be followed and understood in their historical development. But, after the facts, life delivers a virtual certificate, that we can eventually recover as a post mortem, testifying to how things have gone this or that way. The parable - or paradox - of Schrodingers cat (1935) concerns this point, and it seems to imply the belief of quantum theorists that an elementary event cannot be recorded as such until an external observer certifies it. History validates the decision, and resolves the indeterminacy, as only one of the possibilities is assimilated and ‘fossilized’. This end of the scale of events is closer to the minimal scale of construction of living machinery than to any other scale of construction in the universe. Further on in Schriidinger’s parable, two subsystems are associated side by side; one of them is a technical amplifier, the cat killing contraption more comparable to our instruments of war, including the most dissipative part in the whole system - and the other is an organism or a culture, supposedly autopoietic, whose past evolution was guided by constant selection to ‘improve’ and stabilize its capacities as an information managing system. A system that is open, dissipative and autopoietic is expected to show, in combination, all these properties forever. The chain of events that mark the passage of time and make the substance of the autopoietic systems, as living organisms, find in the frame of the temporal or historical matrix in which they are embedded the required frame for a continued record and validation of the events as they happen along the individual life. Just at the same time, this

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role as notary public or registrar may be the dawn of the mind. Conrad (1989, p. 123) is clearly outspoken on this point: ‘The prime feature of measuring instruments and biological systems is that they unmask the latent irreversibility’. When worrying about a photon’s probability of going this way, or that way, wait a moment and the advance of real history will tell, as continuation of life will eventually testify, about the result of the actual accumulation of such elementary events. And this is real information in the making, not symbols for it. If no trace is left, significant for the growth of organization, write it off as ‘entropy’.

have turned to emphasize a rather ‘nonprogressive’ point of view, whatever that means, probably ‘a random walk’ without meaningful changes in the capacity and quality of their information system. Another opinion is that evolution cannot avoid an increase in the amount of information stored and forwarded, eventually signiticant in future history, an eventual signification that cannot be anticipated for sure. Any evaluation of such information selected and accumulated through evolution may try to anticipate if the added information has survival value or, at least, if it refers or applies to increasingly larger extensions of space-time.

6. Ahout progress and progressive change

References

Progress can be associated only with the construction or reconstruction of the stores of information, on the ground provided by the past. Many biologists see evolution as progressive, a concept that might mean that there is a gradual build-up of information, making the organisms more apt to survive and to overcome changes in the environment. However, much of the information being forwarded may not be relevant or may already be obsolete. Significant environmental changes vary from sudden to catastrophic and a rich information store does not guarantee survival, although important acquisitions often manage to be transported across catastrophic changes in earth history. Even without environmental change, a large part of the accumulated information may become obsolete. The deployment of life is the best example of the now fashionable concept of ‘sustainable development’. But, as it is usually presented, it is rather an oxymoron, until development is properly defined; it may make sense if it is accepted that a larger store of information can provide more ‘personal satisfaction’ for every entropy unit contributed to the general cosmic store. Then the recipe may be: spare energy and use cleverly the available information. This is easier said than done. Several biologists who used to be more or less fond of Hegelian and Spencerian views and who believed in progressive evolution, and who were, besides, sympathetic to Marxism, in present days

Conrad, M., 1983, Adaptability: The significance of variability from molecule to ecosystem (Plenum, New York). Conrad, M., 1989, Force, measurement, and life, in: Newton to Aristotle. Toward a Theory of Models for Living Systems, J. Casti and A. Karkqvist (eds.) (Birkhauser) pp. 121-200. Jones, C.G., Lawton, J.H. and Shachak, M., 1994, Organisms as ecosystem engineers. Oikos 69, 373-386. Jggensen, SE., 1992, Integration of Ecosystem Theories: A pattern (Kluwer Academic Publishers, Dordrecht, Boston, London) pp. 383. Kauffman, S.A., 1993, The origins of Order. Self-Organization and Selection in Evolution (Oxford Univ. Press, New York) pp. 709. Mansson, B.A. and McGlade, J.M., 1993, Ecology, thermodynamics and H.T. Odum’s conjectures. Oecologia 93, 582-596. Margalef, R., 1968, Perspectives in ecological theory (Univ. Chicago Press) pp. 111. Margalef, F., 1991, Teoda de 10s sistemas ecologicos (Pub]. Univ., Barcelona) pp. 290. Matsuno, K., 1978, Evolution of dissipative system: A theoretical basis of Margalefs principle on ecosystem. J. Theor. Biol. 70, 23-71. Matsuno, K., 1984, in: Beyond Neo-Darwinism: An introduction to the new evolutionary paradigm, Mae-Wan ho and P.T. Saunders (eds.) (Academic Press, Orlando, FL) p. 83. Murray, B.G., 1992, Research methods in physics and biology. Oikos 64, 594-596. Nicolis, G. and Prigogine, I., 1977, Self-organization and nonequilibrium systems (Wiley-Interscience, New York). Nicolis, G. and Prigogine, I., 1989, Exploring complexity. An Introduction (Freeman and Co., New York) pp. 313. Odum, H.T., 1983, Systems Ecology (John Wiley & Sons, New York) pp. 644. Pauling, L., 1987, Schiidinger’s contribution to chemistry and biology, in: Schriidinger. Centenary celebration of a polymath, C.M. Kihnister (ed.) (Cambridge Univ. Press, Cambridge, London) pp. 225-233.

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Prigogine, I., 1961, Introduction to thermodynamics of irreversible processes (Wiley, New York). Quenette, P.Y. and Gerard, J.F., 1993, Why biologists do not think like Newtonian physicists. Oikos 68, 361-363. Schrodinger, E., 1944, What is Life? The physical aspect of the living cell (Cambridge Univ. Press).

Schrodinger, E., 1935, Die gegenwartige Quantenmechanik (Natutwissenschaften) 823-828, Volohonsky, structural Volterra, V., Biotheor.

Situation in der pp. 23, 807-812,

844-849. H., 1986, Ecosystems memory in the context of dynamics. Ecol. Modelling 33, 59-75. 1937, Principes de biologie mathematique. Acta 3, l-36.