Observation

This was the most popular question answered by candidates.
Many candidates were able to answer questions (a), (b) and (c) fairly well. Although, some candidates mistook relationship for association in (c) which made them give poor answers to questions. Some candidates could not draw a typical pyramid of energy with the levels of feeding given and could not also indicate the energy flow with arrow.

The expected answers are:

(a) (i) Ecosystem:
Is a natural unit consisting/made up of living/biotic/organism and non-living/abiotic elements/factors; interacting to produce a stable system.
(ii) Abiotic environment:
The non-living components of the ecosystem; such as light/pH/water/oxygen/wind/temperature etc.

(b) Ecological factors that are specific to:
(i) Aquatic habitat
Salinity; turbidity; tidal movement; dissolved gases; density; substratum; water current.

(ii) Terrestrial habitat
Humidity; soil; topography; wind; altitude; availability of water.
Note: Spellings must be correct to score in b(i) and b(ii)
          
(c) The relationship between grass and rabbit in a given habitat

• Grass (green plants) can photosynthesize/ manufacture its food;
• Rabbit which cannot manufacture its food feeds on grass;
• During respiratory process, rabbit gives out carbon dioxide as a waste product;
• Grass makes use of the carbon dioxide to manufacture its food;
• Grass during photosynthesis gives out oxygen as a by-product which the rabbit uses for respiration;

When a rabbit defecates/ dies, bacteria/fungi cause its decay, which forms manure that is absorbed as soil nutrients by grass.

(d) Pyramid of energy

Direction of energy flow (EF)
Proper shape of pyramid (PP)

Correctly named feeding levels (FL)/Correctly named examples of the feeding levels