Observation

 

This question was compulsory. Question 6(a) was poorly answered as most candidates could not describe the adaptive behaviours and some candidates mixed both up. Instead of treating colour blending with the environment, some candidates wrote ‘odour blending’. Some candidates could not also spell the examples correctly.
In 6(b), most candidates could not state the structural features of a cockroach with their functions. They merely stated the structures e.g. antennae, wings. In 6(c), although most candidates supplied wonderful answers to this question, some others wrote wrong answers.
In 6(d), this question was well answered by many candidates but some candidates could not spell correctly and some wrote some methods of cooking. In 6(e), many candidates could not list the applications of variation in a human society. In 6(f), many candidates could answer this question correctly.
In 6(g), the term succession was poorly defined by some candidates, although many candidates had the idea but could not write it out properly. In 6(h), candidates answered the questions correctly.

The expected answers are:

(a) Adaptive behaviours

(i) Mimicry: resemblance of an organism to another different organism; as a means of enhancing its chances of survival in its habitat.

Examples:

- Swallow-tail butterfly mimicking a distasteful one;

- stick insect like a dead twig;

- katydid and grasshopper like leaf;

- large spaded giant arum lily mimics poisonous hooded cobra;

- orchid flower mimics female flies;

- cuckoo bee;

- yellow jacket;

- any other correctly named example.

(ii)Camouflage: concealing coloration; that enables an organism to blend with its background; making/rendering it less visible to predators.

Examples:

- Chameleon;

- Octopus;

- Squid;

- Snake;

- Grasshopper;

- Stone fish;

- Zebra;

- Tiger;

- Giraffe;

- Leopard;

- Toad;

- any other correctly named example.

Note: Spellings of examples in (a) (i) and (ii) must be correct to score.

(b) Adaptive features of cockroach to its habitat

- Dorso-ventrally flattened body; for easy movement through crevices and cracks;

- Fore wings are hardened; to protect the delicate hind wings;

- Brown/dark-brown colour; blends with the darkness to prevent detection in its dark habitat;

- hard hind wings; modified for flight to escape from predators;

- long antennae; for feeling/sensation;

- powerful mouth parts/mandibles/maxillae; for chewing;

- large and powerful hind limbs; for fast movement;

- freezing/low temperature/refrigeration

- presence of plantulae, claws and arolia; to hold fast on surfaces

Note: Structure must correspond to function to score. Structure x 1 mark; function x 1 mark. Function alone does not score; Structure alone scores

 

(c)Effects of pests on plants

- They cause mottling of leaves,

- curling and wrinkling of leaves;

- stunted growth and death;

- seeds are covered with spots;

- wilting;

- red or brown pods

- rusty stripes;

- reduced yield;

- damages and destroys the plants;

- causes diseases in plants.

 

(d) Methods of preserving food

- pasteurization;

- refrigeration/freezing/chilling;

- smoking;

- Oil spillage;

- sun drying/dehydration;

- irradiation;

- canning;

- salting;

- fermentation;

- chemical preservation e.g. vinegar.

Note: Spellings must be correct to score.

 

(e) Applications of variation in a human society

- Crime detection through fingerprinting/DNA analysis;

- blood transfusion through blood groups;

- determination of paternity e.g. DNA analysis;

- marriage counselling e.g. genotypes

- identity- DNA analysis, finger prints.

 

(f) Factors leading to competition in a plant population

- Inadequate space/plant density/overcrowding;

- low rainfall/inadequate water;

- inadequate soil nutrients;

- insufficient light/sunlight.

 

(g) Succession

- is a gradual orderly/progressive process;

- that lasts for a period of time;

- in which a community replaces another;

- until a climax/stable community/equilibrium is attained.

 

(d) Disadvantages of burning vegetation before cropping

- Humus/organic matter is destroyed from the soil/reduces soil fertility;

- destruction of mineral elements/carbon/ nitrogen/phosphorus/sulphur;

- it leads to water loss from the soil by evaporation;

- killing important soil organisms/fauna;

- the bare soil could be eroded/exposed to erosion;

- destroys timber/young trees;

- destroys seeds on the floor of the soil;

- migration of animals/other organisms.