True or false? Some traits are considered vestigial because they existed long ago.

What observations did Darwin make on the Galápagos Islands that helped convince him that evolution occurs?

a. The existence of animals that did not fit into Linnaeus's classification system

b. The similarities and differences among cacti and tortoises on the different islands

c. The presence of species he had seen on other tropical islands far from the Galápagos

d. The radioactive age of the rocks of the islands

e. Fossils of human ancestors

Which of the following is an observation or inference on which natural selection is based? (A) Individuals do not vary in their heritable characteristics. (B) Only well-adapted individuals produce offspring. (C) Species produce more offspring than the environment can support. (D) Nearly all of each individual's offspring will survive and reproduce.

Which of the following is not an observation or inference on which natural selection is based?

a. There is heritable variation among individuals.

b. Poorly adapted individuals never produce offspring.

c. Species produce more offspring than the environment can support.

d. Only a fraction of an individual's offspring may survive.

What types of drugs have helped reduce the death rate due to tuberculosis infection, and why have they become less effective more recently?

What are three ways monosaccharides differ from one another?

Which of the following observations helped Darwin shape his concept of descent with modification?

a. Species diversity declines farther from the equator.

b. Fewer species live on islands than on the nearest continents.

c. Birds live on islands located farther from the mainland than the birds' maximum nonstop flight distance.

d. South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.