26: Communities and Ecosystems
- Page ID
- 124043
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Populations typically do not live in isolation from other species. Populations that interact within a given area form a community. The organisms that form a community are found in habitats, physical environments where organisms live. However, only the biotic (living) components are considered part of a community. Scientists study ecology at the community level to understand how species interact with each other and compete for the same resources.
Contributors and Attributions
Modified by Kammy Algiers from the following sources:
- 45.6 Community Ecology- from Biology2e by OpenStax (licensed CC-BY)
- 26.1: Energy and Energy Flow
- Energy flows through a community as a result of trophic interactions. Energy is defined as the ability to do work, or to create some kind of change. Two of the physical laws that govern energy are the first and second law of thermodynamics. Energy flows from producers to consumers and recycled by detritivores and decomposers
- 26.2: Food Chains and Food Webs
- Trophic interactions in a community can be represented by diagrams called food chains and food webs. Organisms in an ecosystem acquire energy in a variety of ways, which is transferred between trophic levels as the energy flows from the bottom to the top of the food web, with energy being lost at each transfer. Modeling of ecosystem energy is best done with ecological pyramids of energy, although other ecological pyramids provide other vital information about ecosystem structure.
- 26.3: Communities
- Communities include all the different species living in a given area. Biotic interactions refer to the relationships among organisms. Competition occurs when organisms at the same trophic level use the the same resources, and one or both organisms is harmed.
- 26.4: Community Interactions
- Herbivory describes the consumption of plants by animals, and it is another interspecific relationship that affects populations. Many plants have evolved defense mechanisms against predation and Herbivory.
- 26.5: Symbiosis
- Many organisms have developed defenses against predation and herbivory, including mechanical defenses, warning coloration, and mimicry, as a result of evolution and the interaction with other members of the community. Two species cannot exist in the same habitat competing directly for the same resources. Species may form symbiotic relationships such as commensalism or mutualism.
- 26.6: Biodiversity in Ecosystems
- The variety of these species is called species richness. Relative abundance is the number of individuals in a species relative to the total number of individuals in all species within a habitat, ecosystem, or biome. In communities, some species play a bigger role than others. keystone species impact the biodiversity within an ecosystem by upholding an ecological community’s structure. Invasive species have an overall negative impact on the community.
- 26.7: Succession
- Community dynamics are the changes in community structure and composition over time. Succession describes the sequential appearance and disappearance of species in a community over time after a severe disturbance.
- 26.8: Ecosystems
- Ecosystems are communities that include the abiotic components of the environment as well.