Describe what is meant by excretion and explain why excretion is necessary for living organisms.

Cambridge International IGCSE Biology (0610) — 1.1 Characteristics of living organisms · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

Excretion is the removal of waste products of metabolism from the body.
It also removes substances that are in excess of the organism’s needs.
Metabolic waste or toxic substances must be eliminated to prevent damage to cells and the organism.
For example, carbon dioxide produced during respiration is a waste product that must be excreted.

Examiner tips

Use the term "excretion" and state it removes metabolic waste and excess substances. Mention a specific waste product such as CO₂. Show understanding of why removal is necessary – to prevent harm to cells.

Common mistakes

Confusing excretion with digestion. Failing to give a specific waste product. Using vague language like "getting rid of stuff" instead of "removal of waste products".

Mark scheme (4 marks)

Excretion is the removal of waste products of metabolism (from the body)
Excretion also involves removal of substances in excess of requirements
Metabolic waste / toxic substances must be removed to prevent harm to the organism / cells
Named example of a metabolic waste product that must be excreted, e.g. carbon dioxide from respiration

Key terms in this question

excretion