Community: Definition, Concept, Structure | Ecology

After reading this article you will learn about:- 1. Definition of Community 2. Concept of Community 3. Structure 4. Dynamics.

Definition of Community:

By definition, community represents the population of all species living and interacting in an area at a particular time. Population can, within limits, adapt to changes in environmental conditions. The major driving force of adaptation to environmental changes is believed by most biologists to be biological evolution, the change in a population’s genetic make up through successive generation.

Concept of Community:

A group of organisms constitute population. Each population has characteristics like natality, mor­tality, age structure, growth dynamics and so on. But when several populations share a common habitat and its resources, they interact among them­selves and develop into a biotic community or sim­ply, a community.

Microorganisms, plants and animals popula­tions sharing a common habitat and interacting among themselves develop into biotic communi­ties. The composition of a biotic community in any habitat is dependent upon the prevalence of environmental conditions in that habitat and the ecological amplitude of species populations.

Thus the climate and other abiotic as well as biotic con­ditions of a habitat determine the type of com­munity which survives and develops. The organ­isms of a community usually exhibit trophic (feed­ing) relationships among themselves. They also interact in sharing the space and there may be in­teractions at a reproductive and behavioural level.

Each biotic community exhibits a number of characteristics, such as diversity, density, dominance, composition and stratification. Each community has its special limit. Sometimes the boundary between two communities may be very sharp or gradual.

The transitional zone or junction between two or more diverse communities is called “eco-tone”. The eco-tone harbours a community termed eco-tonal com­munity with organisms of overlapping communi­ties and some of unique types.

Structure of Community:

Communities may be small, consisting of few spe­cies populations in a small space, or large, com­prising several species populations in a large area. The community structures, composition and other characteristics can be readily described by visual observation without actual measurement.

This is a qualitative approach which is easier than the quantitative population analysis where measure­ments are actually made. Communities usually cat­egories by the ecologists in various ways primarily based of habitat features like water availability, high exposure, or other habitat features.

For instance, depending on the amount of water availability, plant communities may be hydrophytic (aquatic habitats), mesophytic (moderately moist soil habi­tat) and xerophytic (dry or arid habitat).

Similarly communities growing on conditions of abundant light are called heliophytic and those growing in shade sciophytic. Identically communities grow­ing on various habitats designated as desert com­munities, mountain communities and estuarine communities and so on.

In general, a community is dynamic since it changes over time. This dynamic nature is reflected in the succession of organisms in a habitat. A se­ries of changes results in the development of a relatively stable community, which maintains its structure and influences the climate of the area.

Such a stable and mature community is called a climax community, while communities of successional stages are called seral communities. The plant community structures, composition and other characterizes can be described in both qualitative or quantitative means.

Community Dynamics:

Communities are dynamic systems constantly in­teracting with another system, the environment, which is equally dynamic. The community charges are gradual and imperceptible at any time but eas­ily recognisable if observed at regular intervals over a long period of time. Seasonal changes in plant communities always occur at every place, particu­larly in areas where temperature variation is sig­nificant.

However, in course of very long period of time at many places the communities have reached a peak stage and attained a dynamic bal­ance with the environmental changes. The pro­cess of change in communities and their environ­ment at one place in the course of time is called “ecological succession”.