science class 3rd

Question

Below is a diagram indicating the limb bones of a crocodile, a bat, a whale, and a bird. Similar bones are highlighted in the same colors.

Crocodiles, bats, whales, and birds have similar limb bones. What do these similarities suggest?

A.

A similar limb structure evolved in each species independently and by chance.

B.

The common ancestor of birds and crocodiles was a whale.

C.

Crocodiles, bats, whales, and birds evolved from a common ancestor.

D.

Bats and crocodiles share an ancestor with whales but not with birds.

Answer 1

This is a question about evolution, where we examine evidence and ask questions about what the evidence can tell us. In general we've learned from a wide range of evolutionary studies that when there are extensive similarities in bone structure (or other anotomical structures) among groups of animals, then they must have a common ancestor. These limbs are quite similar, aren't they? The colors highlight those similarities.

1. We can reject this first answer because it is completely illogical and unreasonable to suggeste from this evidence that all these groups of animals evolved independently. Why should they have any similarity at all if they do not have a common ancestor.
2. All four of these creatures have similar bone structures... there is no evidence presented that specifically would suggest that whales preceded birds and crocodiles or any other combination for that matter.
3. This answer makes the most sense, it describes the common sense conclusion from everything we've learned about evolution and inheritance of similar characteristics. These four groups all have very similar bone structure in their limbs, and this is evidence of a common ancestor.
4. This is similar to #2... there is no evidence presented that suggests one or more groups descended from one of the others, or could not have descended from one of the others.