Theory question 103
Pollution(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 conservation method. (c) Explain the term adoption. (d) Explain two ways each by which the following organisms adapt to their habitats: (i) hydrophytes; (ii) xerophytes.
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(a)(i) Sewage is liquid and solid waste (faeces, urine, waste water) from homes, industries and farms carried in drains and sewers.
(ii) Any five: oxygen in the water is used up by decomposing bacteria; fish and other aquatic animals die; bad smell; water becomes dirty and unfit to drink; spreads water-borne diseases such as cholera and typhoid; nutrients cause algal bloom (eutrophication); breeding of mosquitoes and other pests; toxic chemicals poison organisms.
(b) Surface terracing: a slope is cut into a series of flat steps (terraces) across the slope. Water flows slowly from step to step instead of rushing down, so less soil is washed away and more water soaks in.
(c) Adaptation (printed 'adoption'): a feature of structure, function or behaviour that helps an organism survive and reproduce in its habitat.
(d)(i) Hydrophytes, any two: large air spaces (aerenchyma) for buoyancy and gas storage; thin or no cuticle; stomata on the upper surface of floating leaves; finely divided submerged leaves resist currents; poorly developed roots and xylem.
(ii) Xerophytes, any two: thick waxy cuticle reduces water loss; sunken stomata or few stomata; leaves reduced to spines or rolled; deep or wide-spreading roots to find water; water-storage tissue in fleshy stems or leaves.
For (d), give the feature and say how it helps the plant.