# Explain how the continuous nature of evolution presents a challenge to the classification of organisms into discrete taxa, and suggest one approach biologists use to address this challenge.

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

## Mark scheme (4 marks)

1. Evolution is a continuous process, so boundaries between species/taxa are not always clear-cut or distinct.
2. Populations that are diverging may still be able to interbreed, making it difficult to assign them to separate species using the biological species concept.
3. The fossil record and living intermediates reveal ancestral forms that do not fit neatly into any single modern taxon.
4. Biologists address this by using phylogenetic/cladistic classification, grouping organisms by shared derived characters (synapomorphies) and common ancestry rather than by overall similarity, producing clades that reflect evolutionary relationships.

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