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Test your understanding
In this module, you learned that homologies are traits that different lineages
inherited from their common ancestor. Homologies are evidence that different
species shared a common ancestor. Analogies, on the other hand, are similar
traits that were not inherited from a common ancestor but that evolved separately.
Analogies often exist because two different lineages became adapted for similar
lifestyles.
Sugar gliders and flying squirrels look amazingly similar. They are both furry
animals of about the same size, with big eyes and a white belly. And they both
glide from treetops using a thin piece of skin that is stretched between their
legs. This piece of skin helps keep them stable while gliding.
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| Flying squirrel |
Sugar glider |
However, these animals also have some key differences:
- Sugar gliders live in Australia, and flying squirrels live in North America.
- Sugar gliders have a pouch (like a kangaroo does), which provides shelter and safety for their tiny babies — at birth, a baby sugar glider is smaller than a peanut! Flying squirrels, on the other hand, have much larger babies and no pouch.
By studying their genes and other traits, biologists have figured out that sugar
gliders and flying squirrels are probably not very closely related. Sugar gliders
are marsupial mammals and flying squirrels are placental mammals.
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