# Explain how the reclassification of organisms using molecular evidence has changed our understanding of evolutionary relationships, using one named example.

> IB DP Biology Standard Level (2023 syllabus) — A3.1 Diversity of organisms · Explain · 4 marks

## Mark scheme (4 marks)

1. Traditional classification was based on morphology / observable physical characteristics, which could lead to grouping organisms that appear similar but are not closely related
2. Molecular evidence such as DNA base sequences / gene sequences / amino acid sequences can reveal true evolutionary relationships / degree of common ancestry
3. Molecular evidence has led to reclassification, with some organisms moved to different taxa / groups previously thought to be related separated / groups previously thought to be unrelated united
4. Named example correctly used — e.g. giant pandas reclassified from Procyonidae (raccoon family) to Ursidae (bear family) based on molecular data; OR fungi reclassified from Plantae to their own kingdom Fungi based on molecular/biochemical evidence; OR whales shown by molecular evidence to be most closely related to hippos / artiodactyls; OR birds reclassified as a clade within reptiles (Reptilia) based on molecular and phylogenetic evidence

## Key terms

- [reclassification](https://www.gradenine.co.uk/glossary/reclassification)
- [molecular evidence](https://www.gradenine.co.uk/glossary/molecular-evidence)
- [evolutionary relationships](https://www.gradenine.co.uk/glossary/evolutionary-relationships)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-reclassification-of-organisms-2a3fb27e) · Published by Druglandscape Ltd.