Community Ecology

Community ecology seeks to answer these and other questions about communities. An ecological community is a group of actually or potentially interacting.
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Consequently, food chains combine into highly complex food webs. Even a simplified food web can show a complicated network of trophic relationships. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind.

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Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Timothy Fridtjof Flannery John N. Page 1 of 6. Next page Keystone species. Learn More in these related Britannica articles: Community ecology , or synecology, considers the ecology of communities, the set of species found in a particular place. Because the complete set of species for a particular place is usually not known, community ecology often focuses on subsets of organisms, asking questions, for example, about….

Community , in biology, an interacting group of various species in a common location. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community. Biodiversity , the variety of life found in a place on Earth or, often, the total variety of life on Earth. A common measure of this variety, called species richness, is the count of species in an area. Colombia and Kenya, for example, each have more than…. Trophic pyramid , the basic structure of interaction in all biological communities characterized by the manner in which food energy is passed from one trophic level to the next along the food chain.

Autotroph , in ecology, an organism that serves as a primary producer in a food chain. Autotrophs obtain energy and nutrients by harnessing sunlight through photosynthesis photoautotrophs or, more rarely, obtain chemical energy through oxidation chemoautotrophs to make organic substances from inorganic ones. Autotrophs do not consume other organisms; they are,…. Help us improve this article!

The number of species occupying the same habitat and their relative abundance is known as the diversity of the community. Areas with low species diversity, such as the glaciers of Antarctica, still contain a wide variety of living organisms, whereas the diversity of tropical rainforests is so great that it cannot be accurately assessed.

Scientists study ecology at the community level to understand how species interact with each other and compete for the same resources. The cycling of snowshoe hare and lynx populations in Northern Ontario is an example of predator-prey dynamics. Perhaps the classical example of species interaction is the predator-prey relationship. Population sizes of predators and prey in a community are not constant over time, and they may vary in cycles that appear to be related.

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The most often cited example of predator-prey population dynamics is seen in the cycling of the lynx predator and the snowshoe hare prey , using years of trapping data from North America Figure 1. This cycling of predator and prey population sizes has a period of approximately ten years, with the predator population lagging one to two years behind the prey population. An apparent explanation for this pattern is that as the hare numbers increase, there is more food available for the lynx, allowing the lynx population to increase as well.

When the lynx population grows to a threshold level, however, they kill so many hares that hare numbers begin to decline, followed by a decline in the lynx population because of scarcity of food. When the lynx population is low, the hare population size begins to increase due, in part, to low predation pressure, starting the cycle anew.

Community ecology in a changing environment: Perspectives from the Quaternary | PNAS

Predation and predator avoidance are strong influenced by natural selection. Any heritable character that allows an individual of a prey population to better evade its predators will be represented in greater numbers in later generations. Likewise, traits that allow a predator to more efficiently locate and capture its prey will lead to a greater number of offspring and an increase in the commonness of the trait within the population.

Such ecological relationships between specific populations lead to adaptations that are driven by reciprocal evolutionary responses in those populations. Species have evolved numerous mechanisms to escape predation including herbivory , the consumption of plants for food.

Defenses may be mechanical, chemical, physical, or behavioral. The a honey locust tree uses thorns, a mechanical defense, against herbivores, while the b foxglove uses a chemical defense: Mechanical defenses, such as the presence of armor in animals or thorns in plants, discourage predation and herbivory by discouraging physical contact Figure 2a. Many animals produce or obtain chemical defenses from plants and store them to prevent predation. Many plant species produce secondary plant compounds that serve no function for the plant except that they are toxic to animals and discourage consumption.

For example, the foxglove produces several compounds, including digitalis, that are extremely toxic when eaten Figure 2b. Biomedical scientists have repurposed the chemical produced by foxglove as a heart medication, which has saved lives for many decades. Many species use their body shape and coloration to avoid being detected by predators. The tropical walking stick is an insect with the coloration and body shape of a twig, which makes it very hard to see when it is stationary against a background of real twigs Figure 3a.

In another example, the chameleon can change its color to match its surroundings Figure 3b. The fire-bellied toad has bright coloration on its belly that serves to warn potential predators that it is toxic. Some species use coloration as a way of warning predators that they are distasteful or poisonous. For example, the monarch butterfly caterpillar sequesters poisons from its food plants and milkweeds to make itself poisonous or distasteful to potential predators.

The caterpillar is bright yellow and black to advertise its toxicity. The caterpillar is also able to pass the sequestered toxins on to the adult monarch, which is also dramatically colored black and red as a warning to potential predators. Fire-bellied toads produce toxins that make them distasteful to their potential predators Figure 4.

They have bright red or orange coloration on their bellies, which they display to a potential predator to advertise their poisonous nature and discourage an attack. One form of mimicry is when a harmless species mimics the coloration of a harmful species, as is seen with the a wasp Polistes sp. While some predators learn to avoid eating certain potential prey because of their coloration, other species have evolved mechanisms to mimic this coloration to avoid being eaten, even though they themselves may not be unpleasant to eat or contain toxic chemicals.

In some cases of mimicry , a harmless species imitates the warning coloration of a harmful species. Assuming they share the same predators, this coloration then protects the harmless ones. Many insect species mimic the coloration of wasps, which are stinging, venomous insects, thereby discouraging predation Figure 5. Several unpleasant-tasting Heliconius butterfly species share a similar color pattern with better-tasting varieties, an example of mimicry. In other cases of mimicry, multiple species share the same warning coloration, but all of them actually have defenses.

The commonness of the signal improves the compliance of all the potential predators.


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Figure 6 shows a variety of foul-tasting butterflies with similar coloration. Go to this website to view stunning examples of mimicry. Resources are often limited within a habitat and multiple species may compete to obtain them. Ecologists have come to understand that all species have an ecological niche: The competitive exclusion principle states that two species cannot occupy the exact same niche in a habitat.

In other words, different species cannot coexist in a community if they are competing for all the same resources. It is important to note that competition is bad for both competitors because it wastes energy. The competitive exclusion principle works because if there is competition between two species for the same resources, then natural selection will favor traits that lessen reliance on the shared resource, thus reducing competition. If either species is unable to evolve to reduce competition, then the species that most efficiently exploits the resource will drive the other species to extinction.

An experimental example of this principle is shown in Figure 7 with two protozoan species: Paramecium aurelia and Paramecium caudatum. When grown individually in the laboratory, they both thrive. But when they are placed together in the same test tube habitat , P. Paramecium aurelia and Paramecium caudatum grow well individually, but when they compete for the same resources, the P.

Community ecology

The organism that benefited is called the commensal while the other organism that is neither benefited nor harmed is called the host. For example, an epiphytic orchid attached to the tree for support benefits the orchid but neither harms nor benefits the tree. The opposite of commensalism is amensalism , an interspecific relationship in which a product of one organism has a negative effect on another organism.

A major research theme among community ecology has been whether ecological communities have a nonrandom structure and, if so how to characterise this structure. Forms of community structure include aggregation [11] and nestedness. From Wikipedia, the free encyclopedia. For human community organized around economic and ecological sustainability, see ecovillage. Proceedings of the Royal Society B: Retrieved 8 March The unified neutral theory of biodiversity and biogeography Print on Demand.

The Quarterly Review of Biology. Biology Botanical terms Ecological terms Plant morphology terms. Category Commons Portal WikiProject. Chemoorganoheterotrophy Decomposition Detritivores Detritus. Archaea Bacteriophage Environmental microbiology Lithoautotroph Lithotrophy Microbial cooperation Microbial ecology Microbial food web Microbial intelligence Microbial loop Microbial mat Microbial metabolism Phage ecology. Ascendency Bioaccumulation Cascade effect Climax community Competitive exclusion principle Consumer-resource systems Copiotrophs Dominance Ecological network Ecological succession Energy quality Energy Systems Language f-ratio Feed conversion ratio Feeding frenzy Mesotrophic soil Nutrient cycle Oligotroph Paradox of the plankton Trophic cascade Trophic mutualism Trophic state index.

Animal coloration Antipredator adaptations Camouflage Deimatic behaviour Herbivore adaptations to plant defense Mimicry Plant defense against herbivory Predator avoidance in schooling fish.

Abundance Allee effect Depensation Ecological yield Effective population size Intraspecific competition Logistic function Malthusian growth model Maximum sustainable yield Overpopulation in wild animals Overexploitation Population cycle Population dynamics Population modeling Population size Predator—prey Lotka—Volterra equations Recruitment Resilience Small population size Stability. Biodiversity Density-dependent inhibition Ecological effects of biodiversity Ecological extinction Endemic species Flagship species Gradient analysis Indicator species Introduced species Invasive species Latitudinal gradients in species diversity Minimum viable population Neutral theory Occupancy—abundance relationship Population viability analysis Priority effect Rapoport's rule Relative abundance distribution Relative species abundance Species diversity Species homogeneity Species richness Species distribution Species-area curve Umbrella species.