There is a widespread opinion among ecologists that ecology lacks general laws. In this paper I argue that this opinion is mistaken. Taking the case of population dynamics, I point out that there are several very general law‐like propositions that provide the theoretical basis for most population dynamics models that were developed to address specific issues. Some of these foundational principles, like the law of exponential growth, are logically very similar to certain laws of physics (Newton's law of inertia, for example, is almost a direct analogue of exponential growth). I discuss two other principles (population self‐limitation and resource‐consumer oscillations), as well as the more elementary postulates that underlie them. None of the “laws” that I propose for population ecology are new. Collectively ecologists have been using these general principles in guiding development of their models and experiments since the days of Lotka, Volterra, and Gause.
Conclusion and Summary
Though there are many problems on the usefulness of the logistic curve, it may be necessary to examine before discussing these problems whether or not the actual data fit to the theoretical values. It has been clarified in this paper that the relation between the population density and its rate of increase per individual described by the differential equation (1) is represented by a straight line on a finite difference diagram on which
N
i+1
−N
i
/
N
i
values are plotted against
N
i+1
. Utilizing this linear relation we may examine the fittness of the logistic curve to the actual data and when it is fitted we may estimate the parameters of the logistic equation by (5) and (6). The result of the application of this method to the experimental populations of azuki bean weevil indicates that the relation between parent and progeny densities fits well to the logistic type as has been proved by
Fujita
and
Utida
(1953) who utilized the linear reltion between 1/
R
+2σ and parent density where
R
is the apparent rate of reproduction and σ is a constant dependent primarily upon the length of adult life (0≦σ≦1).
rate of natural increase, and K is the carrying capacity of the population. The formula can be read as follows: the rate of change in the population (dN/dt)
Population dynamics is the type of mathematics used to model and study the size and age composition of populations as dynamical systems. Population dynamics is a branch of mathematical biology, and uses mathematical techniques such as differential equations to model behaviour. Population dynamics is also closely related to other mathematical biology fields such as epidemiology, and also uses techn
where N is the population size, r is the intrinsic rate of natural increase, and K is the carrying capacity of the population. The formula can be read as follows: the rate of change in the population (dN/dt) is equal to growth (rN) that is limited by carrying capacity (1 − N/K). From these basic mathematical principles the discipline of population ecology expands into a field of investigation that queries the demographics of real populations and tests these results against the statistical models. The field of population ecology often uses data on life history and matrix algebra to develop projection matrices on fecundity and survivorship. This information is used for managing wildlife stocks and setting harvest quotas.
wh…
Bacterial growth dynamics, typically represented by growth curves, are fundamental yet complex features of living populations. Traditional analyses focusing on specific parameters often overlook the full temporal patterns of growth. Here, we systematically investigated how genomic and environmental factors shape bacterial growth dynamics by analyzing 870 growth curves from five Escherichia coli strains with varying genome sizes cultured in 29 chemically defined media. Using dynamic time warping, clustering, and gradient boosting decision trees, we found that environmental components, especially glucose, primarily determine overall growth curve patterns, while genome size governs detailed growth parameters such as lag time, growth rate, and carrying capacity. Notably, finer clustering revealed increased genomic influence and decreased environmental impact, suggesting a hierarchical interaction where the environment modulates broad growth behavior and the genome fine-tunes specific growth responses. These findings provide insights into the coordinated roles of genome and environment in bacterial population dynamics, advancing our understanding of microbial growth regulation.
Malthusian Law of Population. The theory claims that growing population rates contribute to a rising supply of labour and inevitably lowers wages. In essence
The book An Essay on the Principle of Population was first published anonymously in 1798, but the author was soon identified as Thomas Robert Malthus. The book warned of future difficulties, on an interpretation of the population increasing in geometric progression (so as to double every 25 years) while food production increased in an arithmetic progression, which would leave a difference resultin
subsistence severely limits population-level
when the means of subsistence increases, population increases
population-pressures stimulate increases in productivity
increases in productivity stimulate further population-growth
because productivity increases cannot maintain the potential rate of population growth, population requires strong checks to keep parity with the carrying-capacity
individual cost/benefit decisions regarding sex, work, and children determine the expansion or contraction of population and production
checks will come into operation as population exceeds subsistence-level
the nature of these checks will have significant effect on the larger sociocultural system—Malthus points specifically to misery, vice, and poverty
Malthusian social theory influenced Herbert Spencer's idea of the survival of the fittest, and the modern ecological-evolutionary social theory of Gerhard Lenski and Marvin Harris. Malthusian ideas have thus contributed to the canon of socioeconomic theory.
The first Director-General of UNESCO, Julian Huxley, wrote of The crowded world in his Evolutionary Humanism (1964), calling for a world population policy. Huxley openly criticised communist and Roman Catholic attitudes to birth control, population control and overpopulation.
An often quoted passage of Arthur Conan Doyle's story "Silver Blaze" makes the point that the absence of data can be a datum. When the mystery of the purloined racehorse seems insoluble, Police Inspector Gregory asks Sherlock Holmes:… "Is there any point to which you would wish to draw my attention?" "To the curious incident of the dog in the night-time." "The dog did nothing in the night-time." "That was the curious incident," remarked Sherlock Holmes…. The dog that does not bark attracts no attention to itself. It takes insight to recognize that a nonhappening can be an alarm. Herman Daly showed a Holmeslike insight when he called attention to the bark that was absent from a would-be authoritative study made by a group of economists reporting to the prestigious National Research Council in 1986 on population growth and economic development. In 108 pages of text there is not a single mention of carrying capacity, a concept that should be central to all discussions of population and environment. It is as though gravity were left out of a treatise on the dynamics of the solar system; or assets and liabilities were left out of a textbook on business accounting. If civilization survives another century, and if there are still economists, a history of what will then be called "modern economics" may well begin with a belittling account of the "premodern" economics of the twentieth century in which carrying capacity plays no role. Nothing shows so well the impermeability of the barriers between academic disciplines as the silence of economists about a concept that dominates discussions of game management, a discipline concerned with population and environment problems as they affect animals other than Homo sapiens. Economists, dealing only with human populations, probably unconsciously embrace the human exemptionist doctrine (Chapter 15), though their commitment is seldom no more than implicit in their statements (Box 20-1). Two serious criticisms can be leveled against most of the authors quoted in the box. First, it is obvious that they desperately yearn for a world without limits. This is particularly evident in the last quotation, by Gro Harlem Brundtland, who chaired the United Nations commission that issued this statement. One can praise the heart of the commission without agreeing with the head.
Everything we examined (6) — 5 independent sources
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