Describe the roles of producers and primary consumers in a food chain, and explain how energy is transferred between them.

WJEC GCSE Biology (Wales) — 1.6.1 Ecosystems · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

In a woodland ecosystem, oak trees are eaten by caterpillars, which are in turn eaten by blue tits.

Model answer (4 marks)

Producers such as oak trees use light energy to photosynthesise and produce glucose and other organic molecules.
Primary consumers, for example caterpillars, feed on these producers to obtain energy and nutrients.
Energy is transferred along the food chain when one organism eats another.
Only a small fraction of the energy is passed on; most is lost as heat through respiration, or as waste and uneaten material.

Examiner tips

  • Use the exact terms "producers" and "primary consumers". Show the flow of energy from light to glucose to caterpillar. Mention the loss of energy at each step.
  • Include the key point that not all energy is transferred – energy is lost as heat and waste.

Common mistakes

  • Confusing producers with consumers. Forgetting to mention energy loss. Using vague phrases like "food chain" without specifying producers and consumers.

Mark scheme (4 marks)

  1. Producers (oak trees) photosynthesise / use light energy to make glucose / organic molecules
  2. Primary consumers (caterpillars) eat / feed on producers to obtain energy / nutrients
  3. Energy is transferred along the food chain when one organism eats another
  4. Not all energy is transferred / energy is lost at each stage (e.g. as heat through respiration, in waste / uneaten material)

Key terms in this question

producers · primary consumers · food chain

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