Observation

 

Many candidates mixed up the examples of biological associations, hence providing wrong answers by fixing the listed biological associations under wrong headings provided on the table.

Some candidates failed to state the adaptive features of parasites. Some that mentioned the features/structures failed to state the function of the features/structures.
The effects of parasites o their hosts was well answered.

In question 3(c), most of the candidates could define saprophytes satisfactorily but failed to give examples of saprophytes and some of those that gave examples could not spell them correctly.

The expected answers are:

3(a) Table

Parasitism	Mutualism	Commensalism
Tapeworm in the gut of human	Lichen	Remora and shark
Mistletoe and cacao plant	Flowers and honeybee Cattle and white egret	Remora and shark

b (i) Adaptive features of parasites
- possession of specialised organs/haustoria/suckers/hooks; for attachment to the surface of the body of the host;
- specialised piercing/sucking mouthparts; for sucking fluids/blood/plant juices;
- hermaphrodite/ability to reproduce rapidly/easily in large numbers/large quantity of eggs are produced; to propagate their lineage/species;
- large surface area; for absorption of digested food;
- possession of special features/structures/cuticle; to withstand harsh environment/conditions/being digested.
Note: Structure ×1 mark
Function x1 mark
Function alone does not score.

(ii) Effects of parasites on their host
Absorption of nutrients from the body of the host can:
- lead to stunted growth;
- lead to low resistance to diseases in the host;
- lead to loss of blood;
- lead to loss of weight;
- lead to septicaemia;
- cause diseases/injuries/harm;
- lead to death;
- de-value the worth of animal skin/hides/ reduce the value of farm animals.

(ci) Saprophytes
are organisms that feed; on dead/decaying/decomposing organic matter.

(di) Examples of saprophytes
Fungi/ Bacteria/
- Mushroom; - Azotobacter;
- Rhizopus; - Clostridium;
- Mucor; - Streptomycetes;
- Toadstool;
- Mold/mould;
- Penicillium;
- Saccharomyces;
- Aspergillus;
- Yeast.

Note:1. Spellings must be correct to score;
2. Mention of Fungi and Bacteria scores 1 mark each;
3. Where candidates mention other examples with Fungi and Bacteria, examples should be scored;
4. Candidates should not score for correctly named example of fungi and bacteria again, if scores had been awarded in 2.