Energy Flow and Nutrient Cycles

Syllabus tag: KCSE | Biology | Form 3 | Topic 2 Ecology

Lesson objectives

By the end of this topic, you should be able to:

• Construct and interpret food chains and food webs.
• Explain trophic levels and construct ecological pyramids.
• Explain energy flow and the loss of energy between levels.
• Describe the carbon and nitrogen cycles.

Summary

Energy enters an ecosystem through producers and passes along a food chain. Only about 10 per cent transfers between levels, the rest being lost as heat, respiration and undigested matter — which is why chains are short and pyramids taper. Energy flows through an ecosystem and is lost, but nutrients cycle and are used again.