The diagram shows an evolutionary tree in which present-day species branch from a shared common ancestor. A pupil suggests that two organisms with a very si...
Question 1 Report
The diagram shows an evolutionary tree in which present-day species branch from a shared common ancestor.
A pupil suggests that two organisms with a very similar sequence of DNA bases are likely to share a recent common ancestor. Which finding would best support this suggestion?
Answer Details
Since DNA base sequences are inherited, closely related organisms that branched apart recently have had little time to accumulate changes, so their matching genes show only a small number of base differences. Finding few differences between corresponding genes is therefore the direct evidence that two organisms share a recent common ancestor. The other observations are irrelevant to ancestry: differences in the number of legs concern outward form, and where or in which year the organisms were collected tells you nothing about how similar their DNA is.
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