Explain how the fossil record provides evidence for the theory of evolution by natural selection.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Fossils show that organisms that lived in the past were different from organisms alive today, indicating that species have changed over time.
Fossils found in successive rock strata show a sequential change in form, demonstrating gradual change in lineages over geological time.
Transitional fossils show intermediate characteristics between ancestral and descendant groups, providing evidence that one group evolved from another.
The pattern of increasing diversity in the fossil record over time is consistent with populations diverging through natural selection acting on heritable variation.
Fossils found in successive rock strata show a sequential change in form, demonstrating gradual change in lineages over geological time.
Transitional fossils show intermediate characteristics between ancestral and descendant groups, providing evidence that one group evolved from another.
The pattern of increasing diversity in the fossil record over time is consistent with populations diverging through natural selection acting on heritable variation.
Examiner tips
- Use the exact wording from the mark scheme to hit each point. Show the logical sequence: change → stratigraphy → transitional forms → diversity. Keep each point concise and separate with line breaks or bullet numbers.
Common mistakes
- Confusing the fossil record with living species only. Failing to mention the sequential nature of strata. Over‑generalising without citing transitional fossils. Using vague terms like "evolution" without linking to natural selection.
Mark scheme (4 marks)
- Fossils show that organisms that lived in the past were different from organisms alive today, indicating that species have changed over time.
- Fossils found in successive rock strata show a sequential change in form, demonstrating gradual change in lineages over geological time.
- Transitional fossils show intermediate characteristics between ancestral and descendant groups, providing evidence that one group evolved from another.
- The pattern of increasing diversity in the fossil record over time is consistent with populations diverging through natural selection acting on heritable variation.
Key terms in this question
fossil record · natural selection
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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