Communities
In ecology, the term community, or more precisely biotic community, refers to the populations of different kinds of organisms living together and sharing the same habitat.
Organization of a Biotic Community
The structure of a community refers to its characteristic pattern, determined by the following factors:
- The roles played by various populations.
- The range of different populations.
- The type of area inhabited by the community.
- The diversity of species present.
- The interactions among the populations living in the same area.
- Members of a community interact not only with each other but also with their environment. Only those plants and animals that are well-adapted to the prevailing environmental conditions can survive in a given community. Since climate largely determines the environment, it also dictates whether an area supports a forest, grassland, or desert community.
- Communities may also be man-made, such as crop fields or lawns. These artificial communities are relatively simple, often consisting of only one or a few species, and are highly unstable, requiring constant care and maintenance. In contrast, natural communities are more diverse, complex, and self-sustaining.
Stratification of a Community
Stratification refers to the vertical layering of vegetation in a community. Moist tropical rainforests provide an excellent example, where up to five or more distinct layers of vegetation can be observed:
- Ground layer — mosses, liverworts, and organic matter.
- Herb or grass layer.
- Short shrub layer.
- Understorey of short trees.
- Canopy of tall trees.
- Overstorey or emergent layer — tallest trees extending above the canopy.
The canopy dominates the tropical forest, modifying light and moisture conditions for the shorter layers below. Each layer provides unique habitats for specific plants and animals, which differ in their size, behavior, and adaptations. This stratification minimizes competition and conflict, as species occupy different layers and utilize resources differently.
Community Characteristics
One of the most important attributes of a community is its species diversity.
- Species diversity refers to the variety of organisms present in a community and can vary seasonally or between different communities.
- Communities with greater species diversity tend to be more stable, meaning they can return to their original state after a disturbance.
- Species diversity has two components:
- Richness — the number of species present.
- Evenness — the relative abundance of each species.
A community with a higher number of species and a more even distribution of individuals among species is considered to have greater diversity and stability.