Explain.

(a) Population level

(b) Ecosystem

(c) Community

(d) Biosphere

(a) All members of a same species constitute the population level of organisation. For example, the population of humans in a particular area consists of all the individuals (males and females) living in that area. Thus, the total members of a particular species living in a particular area determine the population of that species.

(b) An ecosystem consists of several communities (biotic components) living in a particular area and their interactions with the non-living components (abiotic components). An ecosystem may be as small as an aquarium and as large as an ocean or a forest. It may be natural or man-made as a garden. There are many kinds of ecosystems such as lakes, rivers, seas and forests.

(c) A particular area in which a living organism lives and flourishes is called a habitat. The habitat of an organism consists of biotic and abiotic factors. The populations of various species of living organisms that live together in one particular habitat constitute a community. A single habitat may have single or more such communities of plants and animals.

(d) It is the life−supporting zone of the Earth where all living things exist. It constitutes many ecosystems. It includes the atmosphere, hydrosphere and lithosphere. In a biosphere all biotic and abiotic factors depend on each other.