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This lesson brings together all the key concepts from Topic 4: Natural Selection and Genetic Modification. Use it to consolidate your knowledge, practise extended-response questions and check your understanding of how the different topics link together.
An evolutionary tree (also called a phylogenetic tree) is a diagram that shows the evolutionary relationships between organisms. It represents how species have diverged from common ancestors over time.
Common ancestor
│
┌──────────┴──────────┐
│ │
Ancestor A Ancestor B
│ │
┌────┴────┐ ┌────┴────┐
│ │ │ │
Species 1 Species 2 Species 3 Species 4
| Feature | What It Means |
|---|---|
| Branch point (node) | A common ancestor where two lineages diverged |
| Branch length | Sometimes represents time or amount of genetic change |
| Tips (ends) | Modern-day species (or extinct species if labelled) |
| Closer branches | Species that share a more recent common ancestor are more closely related |
Classification is not static — it is constantly updated as new evidence emerges:
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