The similarity in skin color among different human populations appears to be primarily the result of:
a. Natural selection
b. Convergent evolution
c. Which biological race they belong to
d. A and B are correct
e. A, B, and C are correct

Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?

a. HIV can change its surface proteins and resist vaccines.

b. The patient must have become reinfected with a resistant virus.

c. A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.

d. HIV began making drug-resistant versions of its enzymes in response to the drug.

Evaluate this statement: Evolution is said to occur when new traits accumulate over time, increasing complexity.

Galactosemia is a potentially fatal disease that occurs in humans who lack the enzyme that converts galactose to glucose. If you were a physician treating a person with this disease, which of the following would you have them exclude from their diet?

a. Maltose

b. Starch

c. Mannose

d. Lactose

A species of crayfish that lives in caves produces eyestalks like its above-ground relatives, but has no eyes. Eyestalks in cave-dwelling crayfish are thus ________.

a. An evolutionary error

b. A dominant mutation

c. Biogeographical evidence of evolution

d. A vestigial trait

e. Evidence that evolutionary theory may be incorrect

When H₂ and CO₂ react, acetic acid can be formed spontaneously while the production of formaldehyde requires an input of energy. Which of these conclusions can be drawn from this observation?

a. More heat is released when formaldehyde is produced compared to the production of acetic acid.

b. Compared to the reactants that it is formed from, formaldehyde has more potential energy than does acetic acid.

c. Entropy decreases when acetic acid is produced and increases when formaldehyde is produced.

d. Only acetic acid could be produced under conditions that existed in early Earth.

Which of the following taxonomic levels contains organisms that share the most recent common ancestor?

a. Family

b. Order

c. Phylum

d. Genus

e. Class

The geneticist James Crow wrote that successful scientific theories have the following characteristics: (1) They explain otherwise puzzling observations; (2) they provide connections between otherwise disparate observations; (3) they make predictions that can be tested; and (4) they are heuristic, meaning that they open up new avenues of theory and experimentation. Crow added two other elements of scientific theories that he considered important on a personal, emotional level: (5) They should be elegant, in the sense of being simple and powerful; and (6) they should have an element of surprise. How well does the theory of evolution by natural selection fulfill these six criteria?