# Explain why scientists now use DNA base sequences, rather than physical characteristics alone, to classify organisms into groups.

> Cambridge International IGCSE Biology (0610) — 1.2 Concept and use of a classification system · Explain · 4 marks

## Mark scheme (4 marks)

1. DNA base sequences provide a more accurate measure of evolutionary relationship / relatedness between organisms
2. The more similar the DNA base sequences, the more closely related the organisms
3. Different species living in the same habitat may evolve similar physical characteristics / morphology (but not be closely related)
4. DNA codes for the amino acid sequence in proteins, so protein structure can also be used as evidence of evolutionary relationships

## Key terms

- [DNA base sequence](https://www.gradenine.co.uk/glossary/dna-base-sequence)
- [physical characteristics](https://www.gradenine.co.uk/glossary/physical-characteristics)

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-scientists-now-use-dna-1e48d370) · Published by Druglandscape Ltd.