Bio Chpt 18

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

During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement is most likely to be helpful in correcting this student's misconception?

Characteristics acquired during an organism's life are generally not passed on through genes

Of the following anatomical structures, which is homologous to the wing of a bird

Flipper of a cetacean

Darwin's claim that all life descended from a common ancestor is best supported by

Molecular biology

In the deserts of the southwestern United States, rock formations made from lava flows are found scattered across the sand. The rock pocket mouse, which has dark fur, lives on the black lava rocks. The Apache pocket mouse, which has light fur, lives on the tan sand. Which of the following statements best explains how these two types of mice could have evolved from a common ancestor?

Natural selection favored different fur colors in the different habitats

Which of the following is/are true about natural selection

On average, it favors the survival of more young with adaptive characteristics

The percent of DNA that species A has in common with other species is shown below.Which statement is a valid conclusion that can be drawn from this graph?

Species A and E have the most recent common ancestor, since the bar is highest

Which of the following statements is an inference of natural selection

Subsequent generations of a population should have greater proportions of individuals that possess traits better suited for success

Which of the following cannot be directly acted on by natural selection?

The genotype of an organism

To observe natural selection's effects on a population, which of these must be true?

The population must contain genetic variation

A species that lacks the variation necessary to adapt to a changing environment is more likely to

become extinct over time

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are

examples of convergent evolution and adaptations to a common environment

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that

humans and chimpanzees share a relatively recent common ancestor

Natural selection is based on all of the following except

individuals adapt to their environments and, thereby, evolve

The shape and height of a tortoise's shell influence how high the tortoise can raise its head. A tortoise with a high shell that leaves a large gap can raise its head higher than a tortoise with a lower shell and a smaller gap. In a population of herbivorous tortoises, a shift in the frequency of different shell heights is observed over time. A set of graphs representing the change in frequency of the different shell heights is shown below.Which of the following selection pressures most likelyproduced the shift in frequency

lack of vegetation at ground level