Community ecology deals with the ecology of the groups of different kinds of populations in the area. While, population ecology is the study of individuals of the same species where processes as aggregation, inter-dependencies between individuals and various factors governing such processes are emphasized. The population ecology has an applied significance for various human population oriented socio-economic problems at national and international levels.
The most visible component of the ecosystem is the biotic, the vegetation and animal life. The assemblage of different plants, animals and micro-organisms in any given ecosystem or in any given physical environment is a community. Thus, the forest with various trees, shrubs, herbs, animals, birds and insects and fungi and other micro-organisms is recognized as a community.
Even within the forest which is a major habitat, any microhabitat such as a piece of decaying log, leaf or fruit or a tiny pool of water held in the hollow of a tree may support a community of heterotrophs such as fungi, bacteria, small insects, etc.
In a community the organisms are interdependent—some organisms, called autotrophs (e.g., plants) are synthesizing the food by fixing solar energy in the photosynthetic activity and all others, called heterotrophs (e.g., animals and micro-organisms), are utilizing the energy stored in the plant material or in the autotrophs either directly (herbivores) or indirectly (carnivores and detrivores).
The community is thus essentially a biotic community. Since the plants, animals and microorganisms all interact with each other and cannot be separated. At this stage, the biotic community can be defined as a naturally occurring assemblage of plants, animals and micro-organisms living in the same environment, mutually sustaining and interdependent, constantly fixing utilizing and dissipating energy (Smith, 1977).
However, McNaughton and Wolf (1973) have considered groups of populations with similar ecological functions coexisting in space and time as distinct communities. The forest thus consists of several communities of plants, animals and microorganisms, all of which together constitute the biotic component of an ecosystem.
The biotic communities represent a higher order of biological organisation than populations, yet, communities refer only Id living organisms, and they are not as inclusive as ecosystems.
In other words, the study of communities involves the entire biology of an area, but strictly speaking, it does not involve the specific study of the interactions of plants, animals and micro-organisms with the non-living components of the environment the way ecosystem analysis does (Southwick, 1976).
Some authors such as S. C. Kendeigh (1974) and R. L. Smith (1977) have divided the biotic communities into the following two main types: major or autotrophic communities which together with their habitats, form more or less complete and self-sustaining units except for the indispensable input of solar energy; and minor or heterotrophic communities which are secondary aggregations within the major communities and are not, therefore, completely independent units as far as circulation of energy is concerned. i.e., They depend on major communities for their energy source. For example, any forest forms the major community, while the community existing on any microhabitat which is occurring within the forest is the minor community.
A biotic community has a series of characteristics such as structure, dominance, niche, species diversity, stability, development and a metabolic rate which is not present in its individual species component, but has meaning only with reference to community level of organisation.