ENVIRONMENT - BASIC DEFINITIONS (UPSC) - Environment Notes

BASIC DEFINITIONS

1. Species: It is a set of organisms having a common gene pool and capacity of interbreeding uniformly.

2. Population: It is a group of organisms of the same species. 

3. Community: It is a group of populations of different species living in the same geographical area. 

4. Factor: It is any external force or physical quantity that influences organisms. 

5. Environment: It is the sum of all the factors influencing organisms. 

6. Habitat: It is a set of environmental conditions necessary for the growth of organisms.

7. Ecad: It is a population having certain features specifically induced by the environment which distinguishes it from the similar population living in a different environment. 

8. Ecotone: It is a zone of transition between two communities. 

9. Succession: It is a natural process by which different groups or communities colonize the same area over a period of time in a definite sequence. If succession starts with primitive substratum without any previous living matter it is called primary succession. But if it starts from the existing living matter it is called secondary succession. If an existing community gets replaced on its own due to its interaction with the environment it is called autogenic succession. However, if such replacement takes place due to external factors, it is called allogenic succession. In the natural process of succession, one community gets replaced by another until a stage comes when a type of community cannot be displaced by existing environmental conditions. Such a community is known as the climax community and the stage is known as Climax. 

10. Biome: It is a complex of several types of communities, some at the climax stage and others at various stages of succession. 

11. Ecosystem: It is a collection of all the biotic and abiotic components of the environment which is capable of existence independent of any external factor. 

12. Standing State: It is the number of inorganic substances present in biotic as well as abiotic components of an ecosystem at any given time.