Question 6
(i) Name the two types of competition in an ecosystem.
(ii) List four factors that bring about competition among organisms.
(iii)Explain briefly the role of competition in the process of succession.
- State three ways by which water is lost from living organisms to the atmosphere.
- Name two organisms each which are:
- Fluid feeders:
- Filter feeders.
- State two functions each of the following parts of the mammalian skin:
- Cornified layer;
- Hair erector muscle;
- Sebaceous gland.
- State four factors that can result in overcrowding in a habitat.
- State five benefits of family planning.
Observation
Questions (a) (i) and (ii) were well answered but (a) (iii) was either poorly answered or not attempted. Question 6 (b) was well treated but some candidates wrote translocation, wetting the farm, adding fertilizer, as some of their answers. Some candidates wrote virus, nematodes, bacteria, cockroach, termites as filter feeders while some candidates interchanged the answers for fluid feeders and filter feeders. Question 6 (d) was well treated tool but the functions of sebaceous, gland were fairly treated. Many candidates only wrote what family planning is, without stating the functions.
The expected answers are:
(a) (i) Types of competition in an ecosystem
Interspecific/interspecies; intraspecific/intraspecies competition.
NOTE: Spellings must be correct to score.
(ii) Factors affecting competition
Food/nutrient shortage; overcrowding/space; scarcity of water; inadequate light; temperature variation; inadequate number of mating partners.
- Roles of competition in succession.
Competition leads to death/elimination/emigration of weak organisms; changes are brought about by the replacement of this old species by new ones; new species adapt better than old ones; it gives rise to succession.
OR
Competition for scarce resources; leads to the death of weak organisms; the stronger organisms become more abundant; causing a shift in the make-up of the community; this brings about succession.
(b) Ways by which water is lost from living organisms to the atmosphere
Evaporation; respiration; transpiration; sweating/perspiration; guttation; urination/excretion; defaecation.
NOTE: Spellings must be correct to score.
(c) Examples of
(i) fluid feeders
Mosquito; butterfly; housefly; tsetse fly; moth; aphid; bees; hummingbird; bedbug/bug; tick/any correctly named example.
(ii) filter feeders
Tilapia, tadpole, mosquito larva; whale; shrimp; bivalve-molluscs; sponges; clams; copepod; crayfish/lobster/oyster/ any correctly named example.
NOTE: Spellings must be correct to score.
(d) Functions of parts of mammalian skin
(i) Cornified layer
- Prevents excessive loss of water by evaporation/water proof;
- prevents germs from entering the body;
- prevents mechanical injury/damage to the underlying layer.
(ii) Hair erector muscle
- Causes hair to stand erect/bend;
- aids temperature regulation;
- squeezes the sebaceous gland to produce ebum.
(iii) Sebaceous gland
- Produces sebum which lubricates the hair;
- Keeps the skin soft/smooth;
- Prevents skin dehydration/cracking;
- Prevents bacterial growth.
(e) Factors resulting in Overcrowding
- limited space;
- increase in birth rate/natality;
- decrease in death rate/mortality;
- more immigration;
- less emigration;
- increase in survival rate;
- abundant food/water/resources;
- lack of predation/predators.
(f) Benefits of family planning
- To prevent unwanted pregnancy;
- It prevents population explosion in both family and nation;
- It reduces maternal death rate;
- It ensures good healthcare of the children; and qualitative education for the children;
- It eliminates child dumping;
- It helps the Government to provide adequate social amenities;
- it ensures adequate nutritional care of the children;