Scientists investigated three single-celled organisms, M, N and O, found in rainwater collected from hollows in trees.
The organisms were first classified using their appearance under an early microscope.
| Organism | Appearance under an early microscope | Internal structures seen using an improved microscope |
|---|---|---|
| M | Rounded | Many distinct internal structures |
| N | Rounded | No distinct internal structures |
| O | Long and narrow | Many distinct internal structures |
Scientists later compared the same region of DNA from each pair of organisms.
| Pair of organisms | Percentage of DNA bases that are the same (%) |
|---|---|
| M and N | 71 |
| M and O | 96 |
| N and O | 69 |
Give one observation that could explain why M and N were first placed in the same group.
Explain which two organisms should now be placed in the same small classification group and why the original classification should be revised. Use evidence from both tables.
81 exam-style questions on AQA GCSE Biology 6.4 Classification of living organisms, covering 6.4 Classification of living organisms. Each one has a worked solution and a mark scheme showing where the marks go.