1. Define ecosystem.
2. Identify with examples two main components of the ecosystem.
3. Describe the interdependence between the two main components identified in 8(b) above.
4. In what two ways can environmental balance be achieved?

      This question was very popular among the candidates and they performed well in parts (a) and (b), but the interdependence between the two main components of the ecosystem and the ways of achieving environmental balance was not properly answered by some of the candidates.

     The interdependence between the biotic and abiotic components of the ecosystem are:

• plants depend on soil for support and nutrients;
• all human activities are mainly carried out in the land;
• soil, air and water provide habitat for living organisms;
• food produced from the use of sunlight, water and other gases are consumed by animals;
• some gases such as oxygen and carbon-dioxide are returned to nature through respiration and photosynthesis;
• dead plants and animals are broken down to form soil by bacterial during decomposition.

      The ways of a achieving environmental balance include:

• Hydrological cycle (water cycle)
• Carbon cycle
• Mineral / nutrient cycle
• Nitrogen cycle
• Food chain and food web
• Reforestation.