WAEC Biology 2016 Theory — Question 3

Model answer

(a)(i) A habitat is defined as the natural dwelling place of an organism. (ii) Roles of a decomposer in an ecosystem: Decomposers cause the decay of dead plants and animals They release nutrients into the soil They are crucial to nutrient cycling (b) Energy flow in a freshwater habitat: The sunlight energy is harnessed by photoautotrophs in the water to produce food. A primary consumer feeds directly on the phototrophs (the producer). A secondary consumer is eventually fed on by the tertiary consumer. The tertiary consumer is also eventually feasted on by decomposers. (c)(i) Harmful effects of microorganisms to plants: They reduce crop yields They reduce the quality of the crop They cause diseases in plants (ii) Beneficial effects of microorganisms to humans: They release nutrients from dead plants and animals. These nutrients are then used for further food production. They are useful in tanning of leather. Some micro-organisms are useful during fermentation. Yeasts, a microorganism, is used in baking. Some microbes are useful in the production of antibiotics. Some microorganisms are used in cleaning up oil spillage.