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Similarities and differences: understanding homology and analogy
by the Understanding Evolution team

In everyday life, people look like one another for different reasons. Two sisters, for example, might look alike because they both inherited brown eyes and black hair from their father. On the other hand, two people attending an Elvis impersonators' convention may look alike because they are both wearing rhinestone studded suits and long sideburns. The similarity between the sisters is inherited, but the similarity between the Elvis impersonators is not.

Elvis impersonators do not inherit their similarities

Biological similarity
It works the same way in biology. Some traits shared by two living things were inherited from their ancestor, and some similarities evolved in other ways. These are called homologies and analogies.

homology
traits inherited by two different organisms from a common ancestor

analogy
similarity due to convergent evolution, not common ancestry

In this module, you'll learn more about homologies and analogies and why they are important. We'll start by playing a game to get you thinking about similarities and differences.


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The tale of the limb


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