(a) Short notes:
(i) Niche: Refers to a specific portion of a habitat/dwelling place which is occupied by a particular species of organism. It is also a functional position/role of an organism within the community. Each organism living in the same habitat has its own living space, source of food and tolerance for the effect of the habitat/environment.
(ii) Population density: It is the number of individual organisms of the same species. Per unit area/volume of the habitat at a particular time. It determines the interaction between members of the same species and members of other species. It is mathematically expressed as Total population/population size. It is estimated in humans/animals by counting. In plants by using quadrat.
Area of habitat
(iii) Climax community: Is established when a stable/ unchanging community is attained in ecological succession. The community is in equilibrium with the environment. The vegetation reaches its highest development. The same species of animals, plants/organism re-occur from year to year.
(b) Interaction between biotic and abiotic components of an ecosystem: In an ecosystem the abiotic factors are non-living things (carbondioxide, oxygen, sunlight, soil and water, etc) while the biotic components are plants and animals. Green plants use carbondioxide in the presence of sunlight to produce carbonhydrate/ starch/food. Animals/herbivores feed on carbonhydrate/ plants and release carbondioxide from respiration. Decomposers break down dead plants/animals/organic matters to release nutrients to the soil. These nutrients are absorbed by plants for use in food production/ photosynthesis. Plants give out oxygen during photosynthesis, which is used by animals for respiration.