Observation

Candidates failed to define sewage satisfactorily; some regarded sewage as refuse. Question 3 (a) (ii) was poorly answered. They could not give the effects of releasing sewage into a stagnant water body.

Question 3 (b) was not well answered and poorly attempted.

Adaptation was not properly defined too. Candidates could explain ways by which hydrophytes adapt to their habitat but could not explain well for xerophytes.

The expected answers are:

(a) (i) Sewage
Waste matter/faeces, 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 contours; ploughing 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/aerenchyma in roots/leaves; provide support for bouyancy;
-`    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.

(i) 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; to 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.

NOTE:       Structure x1
Function x1; Function alone will not score.
Function must correspond with structure to score.