Question

Whales, humans, lizards, and birds each have forelimbs that are adapted for different functions, including swimming, using tools, walking, and flying. While different in function, these forelimbs share a similar skeletal structure of the humerus, radius, and ulna. How does a comparison of the forelimbs of these organisms provide evidence for evolution?
A. These homologous structures indicate that these four organisms all share a common ancestor.
B. These analogous structures indicate that whales are descended from organisms that lived on land.
C. These analogous structures indicate that these four organisms all experienced convergent evolution.
D. These homologous structures indicate that humans, whales, and birds all evolved from a lineage of lizards.

Answer 1

Answer:

A. These homologous structures indicate that these four organisms all share a common ancestor.

Explanation:

Homologous structures mean the organs will have similar structure, but not necessarily function (human arm vs whale's flipper). While analogous structures are similar in function but not structure (wings of an airplane vs wings of a bird). Since the question states that they are similar in skeletal structure, we know they must be homologous structures, thereby eliminating B and C. D is not a choice because the question does not provide anything about the order of evolution. Therefore the answer is A. These homologous structures indicate that these four organisms all share a common ancestor.