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Environmental Stochasticity
Environmental stochasticity is a concept within population dynamics that describes random environmental events that result in variation of population size. The fluctuation of population sizes is a result of changes in mortality and reproduction rates of individuals in the population. Extinction Environmental stochasticity results in fluctuating population sizes, which puts both small and large populations at increased risk of extinction, but smaller populations are naturally more vulnerable to extinction. Environmental stochasticity cannot stop or change the trajectory of a population that is trending toward extinction; however, it can either exacerbate or lower the vulnerability of the population. This results in the acceleration or reduction of the rate of extinction depending on the intensity of stochasticity. There is a negative correlation between population sizes and the intensity of environmental stochasticity when the population are under weak Allee effects (i.e. higher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Dynamics
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 techniques from evolutionary game theory in its modelling. History Population dynamics has traditionally been the dominant branch of mathematical biology, which has a history of more than 220 years,Malthus, Thomas Robert. An Essay on the Principle of Population: Library of Economics although over the last century the scope of mathematical biology has greatly expanded. The beginning of population dynamics is widely regarded as the work of Malthus, formulated as the Malthusian growth model. According to Malthus, assuming that the conditions (the environment) remain constant ('' ceteris pari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allee Effect
The Allee effect is a phenomenon in biology characterized by a correlation between population size or density and the mean individual fitness (biology), fitness (often measured as ''per capita'' population growth rate) of a population or species. History and background Although the concept of Allee effect had no title at the time, it was first described in the 1930s by its namesake, Warder Clyde Allee. Through experimental studies, Allee was able to demonstrate that goldfish have a greater survival rate when there are more individuals within the tank. This led him to conclude that aggregation can improve the survival rate of individuals, and that cooperation may be crucial in the overall evolution of social structure. The term "Allee principle" was introduced in the 1950s, a time when the field of ecology was heavily focused on the role of competition among and within species. The classical view of population dynamics stated that due to competition for resources, a population will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species Richness
Species richness is the number of different species represented in an community (ecology), ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the Abundance (ecology), abundances of the species or their Relative species abundance, relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness. Sampling considerations Depending on the purposes of quantifying species richness, the individuals can be Forest inventory#Simple random sampling, selected in different ways. They can be, for example, trees found in an forest inventory, inventory plot, birds observed from a monitoring point, or beetles collected in a pitfall trap. Once the set of individuals has been defined, its species richness can be exactly quantified, provided the species-level Taxonomy (biology), taxo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storage Effect
The storage effect is a coexistence mechanism proposed in the ecological theory of species coexistence, which tries to explain how such a wide variety of similar species are able to coexist within the same ecological community or guild. The storage effect was originally proposed in the 1980s to explain coexistence in diverse communities of coral reef fish, however it has since been generalized to cover a variety of ecological communities. The theory proposes one way for multiple species to coexist: in a changing environment, no species can be the best under all conditions. Instead, each species must have a unique response to varying environmental conditions, and a way of buffering against the effects of bad years. The storage effect gets its name because each population "stores" the gains in good years or microhabitats (patches) to help it survive population losses in bad years or patches. One strength of this theory is that, unlike most coexistence mechanisms, the storage effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abiotic Component
In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them underpin biology as a whole. They affect a plethora of species, in all forms of environmental conditions, such as marine or terrestrial animals. Humans can make or change abiotic factors in a species' environment. For instance, fertilizers can affect a snail's habitat, or the greenhouse gases which humans utilize can change marine pH levels. Abiotic components include physical conditions and non-living resources that affect living organisms in terms of growth, maintenance, and reproduction. Resources are distinguished as substances or objects in the environment required by one organism and consumed or otherwise made unavailable for use by other organisms. Component degradation of a substance occurs by chemical or physical processes, e. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotic Component
An ecosystem (or ecological system) is a system formed by organisms in interaction with their environment. The biotic and abiotic components are linked together through nutrient cycles and energy flows. Ecosystems are controlled by external and internal factors. External factors—including climate—control the ecosystem's structure, but are not influenced by it. By contrast, internal factors control and are controlled by ecosystem processes; these include decomposition, the types of species present, root competition, shading, disturbance, and succession. While external factors generally determine which resource inputs an ecosystem has, their availability within the ecosystem is controlled by internal factors. Ecosystems are dynamic, subject to periodic disturbances and always in the process of recovering from past disturbances. The tendency of an ecosystem to remain close to its equilibrium state, is termed its resistance. Its capacity to absorb disturbance and reorga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onager
The onager (, ) (''Equus hemionus''), also known as hemione or Asiatic wild ass, is a species of the family Equidae native to Asia. A member of the subgenus ''Asinus'', the onager was Scientific description, described and given its binomial name by German zoologist Peter Simon Pallas in 1775. Six subspecies are accepted. The onager is reddish-brown or yellowish-brown and has a broad dorsal stripe on the middle of the back. It weighs about and reaches about head-body length. It is among the Fastest animals#Mammals, fastest mammals, capable of running . The onager had a wider range from southwest and central to northern Asia including the Levant region, Arabian Peninsula, Afghanistan and Siberia; the prehistoric European wild ass subspecies ranged through Europe until the Bronze Age. During the early 20th century, it lost most of its range in the Middle East and Eastern Asia and lives today in Iran, Kazakhstan, Uzbekistan, Turkmenistan, India, Mongolia and China. It inhabits de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wikipedia Student Program
Wikipedia is a free online encyclopedia that is written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and the wiki software MediaWiki. Founded by Jimmy Wales and Larry Sanger in 2001, Wikipedia has been hosted since 2003 by the Wikimedia Foundation, an American nonprofit organization funded mainly by donations from readers. Wikipedia is the largest and most-read reference work in history. Initially available only in English, Wikipedia exists in over 340 languages. The English Wikipedia, with over million articles, remains the largest of the editions, which together comprise more than articles and attract more than 1.5 billion unique device visits and 13 million edits per month (about 5edits per second on average) . , over 25% of Wikipedia's traffic comes from the United States, while Japan, the United Kingdom, Germany and Russia each account for around 5%. Wikipedia has been praised for enabling the democra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
