Define the term 'species' and explain why it can sometimes be difficult to classify an organism into a species.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A species is a group of organisms that can interbreed and produce fertile offspring.
It can be difficult to classify an organism because:
1. Organisms that look very similar may actually be different species, so appearance alone is unreliable.
2. It is not always possible to observe whether two organisms can produce fertile offspring, especially when they are rare or geographically separated.
3. Some organisms reproduce asexually, so the breeding criterion cannot be applied.
It can be difficult to classify an organism because:
1. Organisms that look very similar may actually be different species, so appearance alone is unreliable.
2. It is not always possible to observe whether two organisms can produce fertile offspring, especially when they are rare or geographically separated.
3. Some organisms reproduce asexually, so the breeding criterion cannot be applied.
Examiner tips
- Use the definition first, then give two reasons. Show the breeding criterion and the problem of asexual reproduction. Mention appearance as a misleading clue.
Common mistakes
- Confusing ‘fertile’ with ‘reproduce’. Forgetting to mention asexual reproduction. Using vague phrases like ‘hard to tell’ without explaining why.
Mark scheme (4 marks)
- A species is a group of organisms that can interbreed / reproduce with one another
- to produce fertile offspring
- Some organisms that appear very similar may be classified as different species / it can be hard to tell from appearance alone whether organisms belong to the same species
- It is not always possible to observe whether two organisms can produce fertile offspring / some organisms reproduce asexually so the breeding criterion cannot be applied
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Define and Explain" question →
- Decode the mark scheme abbreviations →
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