The structural component of an ecosystem may be classified under two main types :
(i) Biotic components
(ii) Abiotic components
Biotic components comprise the living organisms present in an ecosystem. These include plants, animals and micro-organisms (bacteria and fungi). The biotic components of an ecosystem has been classified into three groups :(i) Producers (Green plants)
(ii) Macroconsumers (Usually animals
(iii) Microconsumers or decomposers (organisms like bacteria and fungi).
Abiotic components consist of the non living components like light, temperature, water, oxygen, carbon, nitrogen and minerals. Various important abiotic factors have been classified as follows :
(i) Climatic factors. These include light, temperature, precipitation, atmospheric humidity and wind.
(ii) Topographic factors. These include altitude, surface slope and exposure, etc.
(iii) Edaphic factors. These include soil and substratum.
Draw a flow diagram showing typical food chain with energy flow and cycling of materials. Give a few examples of food chains.
â–² Fig. 6.11. A typical food chain with Energy flow and Cycling of materials.
Examples of food chains
(i) Grass → Goat → Man
(ii) Grass → Deer → Man
(iii) Algae → Zooplankton → Fish → Man
(iv) Seed → Rat → Cat → Dog Hawk
(v) Algae → Insects → Frog → Snake → Peacock, etc.
Describe the process of succession on a bare rock.
1. Nudation. Development of bare areas without any form of life.
â–² Fig. 6.12. Stages of biotic succession.
2. Invasion. It is the successful establishment of a species in a bare area. It is completed in migration, establishment and aggregation of species. The species to appear first are lichens, followed by mosses and annual grasses. Mosses grow in bunch and alongwith lichens form a mat over the substratum. They join pioneer community.
3. Competition and co-action. Large number of individuals of the species of a limited place develop competition for food and space.
4. Reaction. It is most important in succession. It is the mechanism of modification of environment through the influence of living organisms (both plants and animals). Changes take place, annual grasses, perennial herbs, shrubs and finally trees along with their characteristic animal communities appear. There is accumulation of soil.
5. Stabilization. The final terminal community called climax community formed in forests or grasslands is not replaced and becomes more or less stabilized for a longer period of time. To reach at the climax stage may take hundreds of years.
The fourth stages of succession will have the greatest diversity of species.
For Examples
The following services are provided by forests ecosystem.
1. Purification of air.
2. Mitigation of droughts and floods.
3. Cycling of nutrients
4. Providing habitat and shelter to a number of wild life.
5. Act as storehouse of carbon
6. Influence the hydrological cycle.
7. Maintain biodiversity.
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