(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 adaptation. (d) Explain two ways each by which the following organisms adapt to their habitats: (i) hydrophytes (ii) xerophytes.
Explanation
(i) Sewage : Waste matter/ feaces, urine, waste water from animals/industrial/domestic sources; that is dissolved/ suspended in water. (ii) Effects of releasing untreated sewage into a stagnant water body;
Spread of water-borne diseases/correctly named diseases/microbes/pathogens May be toxic/poisonous to aquatic life/organisms Makes water unfit for consumption/use Increased decomposition Increased concentration of nutrients Rapid growth of algae/aquatic plants/algal bloom/eutrophication Depletion of oxygen Suffocation/death of aquatic animals Generates offensive odour/air pollution Nutrient/nitrate/phosphate enrichment/accumulation in a water body; as a result of breakdown by bacteria.
(b) Surface terracing as a soil conservation method : A method of controlling erosion on a gentle/steep slope of hill; flat horizontal areas are constructed on which crops are cultivated; following the contour; steps/walls are built along the contous; plughing is also done along the contours; reduces the speed of water running down the slopes. (c) Adaptation : Is the possession of the characteristic/trait/behaviour/structure/feature; that evolved over a period of time; enable an organism to survive and reproduce; in response to changes in the environment/habitat. (d) Adaptation of; (i) Hydrophytes
Some hydrophytes lack/have reduced roots/root hairs/root caps do not need firm anchorage in water/wetland presence of large air space parenchyma in roots/leaves; provide support for buoyancy Presence of hairs on the leaves; to prevent blockage of the stomata stomatal pores; occur only at the upper epidermis of the leaves to aid transpiration/loss of water numerous adventitious roots and root hairs; aid the absorption of water/mineral salts small size of the plant; for buoyancy/floating in water waxy upper surface of the leaf; to prevent clogging of the leaf by water long petiole/leaf stalk to support/ expose the broad lamina for photosynthesis long flower stalk/pedicel; to expose flower for pollination/ pollinating agents presence of breathing roots/pneumatophores; for breathing/gaseous exchange.
Xerophytes
possession of thick succulent leaves/stem; for storing water reduction of leaves to spines; to reduce water loss/rate of transpiration thick waxy cuticle on epidermis; to reduce water-loss/transpiration possession of long tap root system; tp obtain water from great depth of soil presence of sunken stomata; to reduce water loss reduced number of stomata; to prevent excessive water loss possession of multiple epidermal layers; for water conservation/to reduce water loss.
