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Cybernetics, a science concerned with understanding how systems are regulated, has reflected the preoccupations of the century in which it was born. Regulation is important in twentieth century society, where both machines and social organizations are complex. Cybernetics focused on and became primarily associated with the homeostasis or stability of system behavior and with the negative feedbacks that stabilize systems. It paid less attention to the processes opposite to negative feedback, the positive feedback processes that act to change systems. We attempt to redress the balance here by illustrating the enormous importance of positive feedbacks in natural systems. In an article in the American Scientist in 1963, Maruyama called for increased attention to this topic, noting that processes of change could occur when a "deviation in anyone component of the system caused deviations in other components that acted back on the first component to reinforce of amplify the initial deviation." The deviation amplification is the result of positive feedback among system components. Maruyama demonstrated by numerous examples that the neglect of such processes was unjustified and suggested that a new branch of cybernetics, "the second cybernetics," be devoted to their study.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract
The concept of feedback must be classed with the seminal ideas of the century, and has become, as Judson (1980) expressed it, “one of the chief themes of scientific understanding.” Actually, the idea was implicit in human technology long before the term “feedback” first appeared in print in 1920. Automatic feedback control devices were used in water clocks (Ctesibius of Alexandria, 3rd century B.C.) and later as regulators on furnaces (16th century) and governors on steam engines (Watt, 18th century). In the 19th century James Clerk Maxwell wrote the first paper describing the theory of feedback devices.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

2. The Mathematics of Positive Feedback

Abstract
Concomitant with the cybernetics revolution of the past half century has been the rapid development of mathematical modeling in the biological and ecological sciences, a methodology now firmly established. A model may be defined as an abstract description of the real world, a simple representation of more complex forms, processes, and functions of physical phenomena or ideas (Rubinstein, 1975). Models have aided in the understanding of ecological systems. When a model is put into explicit mathematical form, it can be analyzed to predict the effect on all parts of the system of external intervention on any single part.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

3. Physical Systems

Abstract
The behavior of complex biological and ecological systems seems at first sight rather remote from the dynamics of inanimate matter. Yet common threads run from the simplest of physical interactions to the most intricate processes in an ecosystem. One such thread, positive feedback, is prevalent in all manner of every day and exotic physical and chemical phenomena. We will follow this strand through a diversity of inanimate systems in this chapter and will see that it leads us to the biological and ecological systems that are the subjects of later chapters.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

4. Evolutionary Processes

Abstract
The evolution toward life on earth involved processes occurring in its primeval waters or mud. The examples in the preceding chapter show that evolution toward more and more complex organic molecules under these primal conditions was not only possible but favored. Prigogine et al. (1972a, b) and Nicolis and Prigogine (1977) have speculated on the relevance of dissipative structures to prebiotic evolution. Short-wavelength solar radiation provided a flow of free energy into the original “soup” of inorganic compounds constituting the earth’s primeval seas. This resulted in the continual synthesis of simple carbon-based compounds. These simple compounds would have occasionally joined to form stable molecules of greater complexity.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

5. Organism Physiology and Behavior

Abstract
The life cycle of an individual living organism involves initial growth in size and complexity, along with maintenance of its fundamental integrity until its reproductive capability is completed. In this section we shall discuss some of the feedback loops involved in such life cycles, particularly as they relate to the physiology and behavior of animals.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

6. Resource Utilization by Organisms

Abstract
The annual produce of the land and labour of any nation can be increased in its value by no other means, but by increasing either the number of its productive labourers, or the productive powers of those labourers who had before been employed. The number of its productive labourers, it is evident, can never be much increased, but in consequence of an increase in capital, or of the funds destined for maintaining them. The productive powers of the same number of labourers cannot be increased, but in consequence either of some addition and improvement to those machines and instruments which facilitate and abridge labour; or of a more proper division and distribution of employment. In either case an additional capital is almost always required. It is by means of an additional capital only, that the undertaker of any work can either provide his workmen with better machinery, or make a more proper distribution of employment among them.” The quote is from The Wealth of Nations (Adam Smith, 1776), and it introduces the idea of the relationship between reinvestment in capital and increased production.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

7. Social Behavior

Abstract
The study of social behavior encompasses such questions as why social groups form among individuals of a species, why they are of certain sizes and not others, and what the realtionships are among group members. A theory that has emerged for animal sociality, called sociobiology (Wilson, 1975), is grounded on Darwinian natural selection acting on the individual, and on the modern principles of population dynamics and ergonomics (the study of work, performance, and efficiency). There is almost universal agreement that sociobiology has been highly successful in its application to animal populations, though there is sharp disagreement on its relevance to human society (Wilson, 1978; Alexander, 1979; Sahlins, 1976; Bock, 1980; Lumsden and Wilson, 1981; Singer, 1981).
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

8. Mutualistic and Competitive Systems

Abstract
The simplest and most obvious positive feedback interaction between species is mutualism. Direct interspecies mutualism can result from a multitude of interactions involving dispersal, shelter, nutrient cycling, energy provision and reproduction (Boucher et al., 1982; Faegri and Van der Pijl, 1966; Heinrich and Raven, 1972; Muscatine and Porter, 1977; Whittaker, 1975; Howe, 1977; Temple, 1977). Mutualistic interactions also arise when mutualists mediate competitive or predator-prey interactions (Wright, 1973; Janzen, 1969; Addicot, 1979; Messina, 1981; Osman and Haugsness, 1981; Heithaus et al., 1980).
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

9. Age-Structured Populations

Abstract
Life, in part, is a process of aging; individuals are born, they mature, and at some point they die. The aging process has a direct effect on individual probabilities of survival and reproductive activity, as well as on total population size. For example, fecundity is zero until the age of reproductive maturity; it then increases and remains high through adulthood, finally declining in old age. Mortality, on the other hand, is usually high in the very young and very old individuals, and lower for adults. Any detailed description of population dynamics must take the age- dependent nature of these variables into account.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

10. Spatially Heterogeneous Systems: Islands and Patchy Regions

Abstract
Perhaps the single greatest discrepancy between traditional mathematical models of population dynamics and populations in the real world is the customary neglect of spatial heterogeneity in the models. Levin (1979) has remarked that, while the statistical description of spatial pattern in ecosystems is relatively well developed (s. especially Pielou, 1977), the description of the dynamics giving rise to such spatial patterns is not. All ecological systems exist on landscapes (or seascapes) of varying complexity, and the dynamics of populations and processes cannot be divorced from these spatial contexts, but mathematical models of spatially extended ecosystems are difficult and the numerical evaluation of the behavior of even only moderately realistic models is far beyond the capabilities of the fastest computers.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

11. Spatially Heterogeneous Ecosystems: Pattern Formation

Abstract
No curious person can look out over the valley of a river or stream without wondering at the obstinate refusal of the water to flow in a straight line from higher to lower ground, even when the terrain is gentle enough to allow it the opportunity. Instead, the river meanders, snake-like down the valley. This phenomenon is so counterintuitive that the nineteenth century sociologist Lester Ward offered it as an example of nature’s wastefulness of energy (see Worster, 1977, p. 175).
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

12. Disease and Pest Outbreaks

Abstract
Until recent times, the periodic irruptions of infectious diseases have been significant factors in the lives of humans and in the history of civilized society. Today many of the serious infectious diseases of humankind have been controlled. However, the increased control of human infectious disease has not lessened the importance of studying and understanding infectious diseases, because agricultural crops as well as forest resources are continually damaged by outbreaks of pests and disease. Strategies for their elimination or control are urgently needed.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

13. The Ecosystem and Succession

Abstract
Up to this point, the types of positive feedback considered have involved single species or communities of species. The ecosystem, however, includes not only interactions among species, but also interactions between species and their physical and chemical environment, therefore involving such factors as energy flow, nutrient cycles, soil conditions, and microclimate.
Donald L. DeAngelis, Wilfred M. Post, Curtis C. Travis

Backmatter

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