Observation

Many candidates attempted this question and were able to define ‘habitat’. They were able to state the keywords that made them score all the marks allocated to the question. However, some candidates wrote that a habitat is an environment.

In question 3(a)(ii), some candidates wrote that decomposers bring about decay of organisms instead of decay of dead organisms. Majority of the candidates could not relate the role of decomposers to the release of offensive gases/odour.

Majority of the candidates that did not get the marks in question 3(b) failed to write that the sun is the source of energy.

The performance of candidates in questions 3(c)(i) and (ii) was average.                                        

 

The expected answers are:

 

• (a) (i) Habitat

The natural dwelling place; of an organism. OR

A place/locality where an organism lives successfully.            

 

                  (ii) Role of a decomposer in an ecosystem

Decomposers are organisms which bring about the decay of dead parts/whole of plants/animals; to produce manure/humus; they release nutrients in them into the soil; which are absorbed by roots of plants; and are used to build up new plant tissues; they thus help in nutrient recycling; also release offensive gases/odour which pollute the air.                         

            (b) Energy flow in a freshwater habitat

Common aquatic plants/ Pistia/Spirogyra/any correctly named aquatic plant; using energy from the sun; photosynthesize/produce food; the food is eaten by primary consumers/animals; small aquatic animals would be eaten by bigger aquatic animals/ secondary consumers; tertiary consumer/a much bigger fish/any correctly named fish

will feed on secondary consumer; in the process of feeding energy flows from one trophic level to another; decreases progressively; dead animals/plants decompose;

energy is lost. 

NB: If the energy does not come from the sun, there is no energy flow.                  

 

            (c) (i) Harmful effects of microorganisms to plants

• - They cause diseases;
• - They can cause undesirable qualities in plants/plant products;
• - They cause spoilage;
• - They lead to wastage;
• - Reduction in yield.

 

     (ii) Beneficial effects of microorganisms to humans

• - Bacteria/decomposers help to decay/decompose dead organisms to release nutrients;
• - Bacteria is used in cleaning/mopping up oil spillage;
• - Used in the fermentation of foods/cocoa beans/garri/locust beans/kenkey production;
• - Used to make vinegar;
• - Used in making alcoholic beverages/wine/beer/spirit;
• - Used in making some antibiotics/penicillin;
• - Used in the manufacture of insulin;
• - Used in making cheese/yoghurt/bread/ Single Cell Proteins;
• - Used in making flax/tanning of leather;
• - Production of some vitamins;
• - Sewage treatment.