Explain how the phenotype of an organism is determined by both its genotype and the environment. Use examples in your answer.

WJEC GCSE Biology (Wales) — 2.4.1 Variation · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

The phenotype is the observable physical characteristics of an organism.
The genotype, i.e. the alleles present, determines the potential for those characteristics.
Environmental factors can modify the expression of the genotype, altering the phenotype.
For example, a plant with the same genotype can grow tall in rich soil but remain short in poor soil, showing environmental influence on phenotype.

Examiner tips

  • Use the exact definition of phenotype and genotype. Show the interaction between genotype and environment. Give a clear, relevant example. Keep the answer concise and to the point.

Common mistakes

  • Confusing genotype with phenotype. Giving an example that only involves genetic variation, not environment. Using vague terms like "environment" without specifying a factor.

Mark scheme (4 marks)

  1. The phenotype is the physical characteristics / observable features of an organism
  2. The genotype (the alleles present) influences the phenotype
  3. Environmental factors can also affect the phenotype
  4. A valid, relevant example of environmental influence on phenotype

Key terms in this question

phenotype · genotype · environment

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