Exterrral and Internal EnvironmentLet us try to understand the concept of environment with some examples. Can you identify the environment of a single carp fish in the pond?Its environment consists of abiotic components sych as light, temperature, water in which nutrients, oxygen, other gases and organic niatter are dissolved. The biotic environment consists of microscopic plankton as well as higher plants and animals and decomposers. The plants are of different kinds such as phytoplankton, partly submerged plants and plants and trees growing around the edge of the pond. The animals consist of zooplankton, insects, worms, molluscs, tadpoles, frogs, buds and various kind of fishes. The decomposers are the saprouophs.
The environment of the fish described above is its external environment. Living organisms also possess an internal environment, enclosed by the outer body surface. The body surface acts as an exchange banier between the ex'temal and the internal environment (Figure a & b show nbelow) and Ecosystem. In the case of unicellular organisms however, the boundary of the cell is also the boundary of the organism. The exchange of materials in single celled organisms is camed out directly with the external environment to which they are exposed.The internal environment is relatively stable as compared to the external environment. However, it is not absolutely constant. Injury, illness or excessive stress upsets the intemal environment. For example, if a marine fish is transferred to a fresh water environment, it will not be able to survive.