(a)(i) What is sewage? (ii) State five effects of releasing untreated sewage into a stagnant water body. (b) Explain surface terracing as a soil conservatio...

(a)(i) Sewage is the liquid and solid waste matter, including human excreta, waste water and refuse, that is carried away from homes, industries and towns in drains and sewers.

(ii) Five effects of releasing untreated sewage into a stagnant water body

• It causes water pollution, making the water unfit for drinking and domestic use.
• It introduces disease-causing organisms (typhoid, cholera, dysentery).
• It promotes rapid growth of algae (eutrophication), forming an algal bloom.
• Decomposition of the sewage and dead algae by bacteria uses up dissolved oxygen, killing fish and other aquatic organisms.
• It produces foul (offensive) odours and breeds mosquitoes and other vectors.

(b) Surface (bench) terracing: this is a soil-conservation method used on steep slopes in which the slope is cut into a series of broad, level, step-like platforms (terraces) supported by ridges or walls along the contour. The flat terraces reduce the speed of run-off water, allow it to soak into the soil, and so check soil erosion while retaining water and nutrients for crops.

(c) Adaptation is the possession of special structural, physiological or behavioural features that enable an organism to survive and reproduce successfully in its particular environment.

(d) Two ways each of adaptation

• (i) Hydrophytes (water plants): possess many large air spaces (aerenchyma) for buoyancy and gaseous exchange; have poorly developed roots and thin/dissected leaves; stomata are on the upper leaf surface (in floating leaves).
• (ii) Xerophytes (dry-habitat plants): have reduced leaves or spines and a thick waxy cuticle to reduce water loss; have sunken stomata and deep or extensive roots; store water in fleshy (succulent) tissues.