Answer
a. Body parts of organisms that perform specific functions are called organs. Examples include the heart, lungs, and liver in humans.
b. If species have homologous structures, it indicates that they share a common ancestor.
c. The more similar two structures are, the more likely it is that the species have evolved from a recent common ancestor.
d. Analogous structures are body parts that perform similar functions but differ in structure. The wings of flies and birds are examples.
e. The existence of analogous structures indicates that species are not closely related.
3. Body parts that have lost their original function through evolution are called vestigial structures. The appendix in humans is an example.
a. The best explanation for vestigial structures is that they were once functional in ancestral species but have become unnecessary over time.
b. Whales have a tiny pelvic bone, which is a vestigial structure for walking on land, as they have evolved to live exclusively in water.