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Line 1: − + − A popular aspect of ecology is the relationship of the relative proportions of predator and prey. When more predators are introduced to an environment, they eat more prey animals. This tends to increase the population of predators, since they get more food and can thus live longer to reproduce more. But it also reduces the food supply of the predators, which contrariwise causes the predators to live shorter lives and to reproduce less. However, since predators tend to eat herbivores, increased predation of herbivores will allow [[plants|primary producers]] to increase in popularion, creating a phenomenon called a Trophic Cascade <ref>Estes, James A. and Terborgh, John, ''Trophic Cascades: Predators, Prey, and the Changing Dynamics of Nature''. Island Press, 2010. ISBN 10597264873.</ref> In some ecosystems, the populations of predator and prey cycle up and down wildly, but usually they reach an equilibrium.<ref>Rockwood, Larry L. ''Introduction to Population Ecology''. Wiley Blackwell, 2006. ISBN 9781405132633. Chapter 10.</ref> + − {{quotebox|The first significant contribution to the theory of population ecology was that of [[Thomas Malthus]], an English clergyman, who in 1798 published his Essay on the Principle of Population. Malthus introduced the concept that at some point in time an expanding population must exceed supply of prerequisite [[natural resources]], i.e., population increases exponentially resulting in increasing competition for means of subsistence, food, shelter, etc. This concept has been termed the "Struggle for Existence". [http://ipmworld.umn.edu/chapters/ecology.htm]}} − + + + + + + + + + + + + + + + + + + + + + + + + + +
Greatly expanded on definition, added sections on organization and popualtions
'''Ecology''' is 'the study of the interrelationships between organisms and their natural environment, both living and non-living'<ref>Martin, E. and Hine, R. (2008) 'A Dictionary of Biology' Oxford University Press, Oxford, U.K.</ref>
'''Ecology''' is a field of [[biology]] that studies "the distribution and abundance of [[organism|organisms]] and the interactions that determine distribution and abundance."<ref>Begon, M., Harper, J. L., & Townsend, C. R. (2006). Introduction: Ecology and its Domain. In Ecology: From Individuals to Ecosystems (4th ed., pp. xi-xii). introduction, Blackwell.</ref> These interactions include both biotic (occurring between living individuals) and abiotic interactions (occurring between and individual and its environment). There are several subdisciplines of ecology that focus on different [[Ecology#Organizational Complexity|levels of organization]] and different types of interactions, such behavioral, disease, sensory, and functional ecology.
Ecology is often confused with [[environmentalism]]. While familiarity of the term "ecology" emerged with the growing environmental concerns of the [[The Sixties|1960s]] and [[The Seventies|'70s]], the two have separate meanings and goals. Ecology seeks to understand natural phenomena in the environment whereas environmentalism is a social and political movement.<ref>Institute of Food and Agricultural Sciences. (n.d.) Confusing Ecology with Environmentalism. Fort Lauderdale. University of Florida Extension.</ref> Even though they are separate, the two are closely related, as environmentalism relies on data and evidence from ecologists to support their [[Environmental Issues|goals]] and ecologists apply their findings to [[conservation]] efforts and management strategies.
Ecology is an established [[science]], but the term is often confused with or used interchangeably with [[environmentalism]].
==Organizational Complexity==
The discipline of ecology is split up into several subfields, ranging in order of organizational complexity. The smallest field of ecology, is organismal ecology, focusing on the the [[adaptation|adaptations]] and [[physiology]] of an individual. [[Population]] ecology is focused on the interactions that individuals of the same [[species]] have, affecting their population dynamics. [[Community]] ecology investigates how populations of different species interact and affect community composition. [[Ecosystem]] ecology incorporates the abiotic factors that influence individuals, populations, and communities. The largest scale of ecology studies the entire [[biosphere]], specifically the processes that occur in it, how changes in climate and organismal abundance affect it, and reconstruct previous climates and ecosystems on [[Earth]].
Though [[evolution|evolutionary biology]] is a separate field of biology, the two are tightly linked, each not fully explaining phenomena without the other. G. E. Hutchinson combined the two topics through the metaphor of an "evolutionary play in an ecological theater,"<ref>Hutchinson, G. E. (1973). The Ecological Theater and the evolutionary play. Yale Univ. Press.</ref> and as T. G. Dobzhansky states, "nothing in evolution makes sense except in the light of evolution."<ref>Dobzhansky, T. (1973). Nothing in biology makes sense except in the light of Evolution. The American Biology Teacher, 35(3), 125–129. https://doi.org/10.2307/4444260.</ref> While evolution is still heavilly debated and studied, it is important to take it into account when studying each of the levels of organization and to make sense of adaptations, distributions, and life histories.
==Population Ecology==
Population ecology is concerned with the interactions between members of a single species. A population is defined as a group of potentially interacting individuals of the same species that occupy the same area and can interbreed, for [[Reproduction|sexually reproducing]] species.<ref>Encyclopædia Britannica, inc. (n.d.). Population ecology. Encyclopædia Britannica. Retrieved March 9, 2022, from https://www.britannica.com/science/population-ecology </ref> The geographic area that defines a population can be distinct, such as an isolated lake or mountain peak, or it can be subjective, based upon the goal of the scientist studying the population.<ref>Begon, M., & Harper, J. L. (2006). Life, Death and Life Histories. In C. R. Townsend (Ed.), Ecology: From Individuals to Ecosystems (4th ed., pp. 89–131). chapter, Blackwell.</ref>
Interactions that occur in populations are said to be interspecific. The most prominent of these interactions is competition for resources, such as water, food, shelter, and mates. Competition can be strong, where individuals control large territories to secure resources, or it can be less strong, such as in eusocial species like [[humans]] and [[wolves]].
=====Modeling=====
Population dynamics is an important aspect of population ecology that studies how populations change in size and density. Two important growth models are the exponential and logistic growth curves. The exponential growth equation is as follows: ''N<sub>t</sub> = N<sub>0</sub>e<sup>rt</sup>'', where ''N'' is the population size at time ''t'', ''e'' is Euler's number, and ''r'' is the intrinsic growth rate. This model predicts a population continually growing faster and faster without bound. Exponential growth is rare in nature, but examples include [[bacteria]] and [[humans]].
Most populations in nature do not grow exponentially, they reach a certain density threshold that limits growth, called the carrying capacity. [[Thomas Malthus]] described how at some point in time an expanding population must exceed supply of prerequisite [[natural resources]], i.e., population increases exponentially resulting in increasing competition for means of subsistence, food, shelter, etc. This concept has been termed the "Struggle for Existence". Resources may be plentiful at small population sizes, so initially a population will appear to grow exponentially, however, as resources become less available due to competition, the population growth rate slows down. This is described the by the logistic growth model as follows: ''dN/dt = rN[(K - N) / K]'', where ''K'' is the carrying capacity. Once a population has reached its carrying capacity, it will often remain at that population size, with stochastic fluctuations. Most populations follow this model.
=====Metapopulations=====
Modern approaches to population ecology have incorporated the concept of metapopulations. Inspired by the work of E. O. Wilson and R. H. Macarthur's work on island biogeography, metapopulations are important for discussing smaller populations that are connected to other nearby populations through colonization, [[emigration]], and [[extinction]]. Certain populations can act as sources for the metapopulations whereas others act as sinks and cannot sustain their own populations. Metapopulations have important conservation concerns, as increased habitat fragmentation increases the liklihood of local extinction of a species. Prioritizing which "islands" in a metapopulation should be protected can help to preserve and maintain healthy populations of charismatic species, such as butterflies and birds.
==References==
==References==