TLS Online TPP Program

#Question id: 4703


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

#Section 2: Evolution
  1. HIV can change its surface proteins and resist vaccines.

  2. The patient must have become reinfected with 3TC-resistant viruses.

  3. HIV began making drug-resistant versions of reverse transcriptase in response to the drug.

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

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TLS Online TPP Program

#Question id: 4644

#Section 2: Evolution

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

According to this tree, what percent of the species seem to be extant (i.e., not extinct)?

TLS Online TPP Program

#Question id: 4645

#Section 2: Evolution

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

Which of the five common ancestors, labeled V—Z, has given rise to the greatest number of species, both extant and extinct?

TLS Online TPP Program

#Question id: 4646

#Section 2: Evolution

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

Which of the five common ancestors, labeled V—Z, has been least successful in terms of the percent of its derived species that are extant?

TLS Online TPP Program

#Question id: 4647

#Section 2: Evolution

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. Which of the five common ancestors, labeled V—Z, has been most successful in terms of the percent of its derived species that are extant?

TLS Online TPP Program

#Question id: 4648

#Section 2: Evolution

In a hypothetical environment, fishes called pike-cichlids are visual predators of algae-eating fish (i.e., they locate their prey by sight). If a population of algae-eaters experiences predation pressure from pike-cichlids, which of the following should least likely be observed in the algae-eater population over the course of many generations?

TLS Online TPP Program

#Question id: 4649

#Section 2: Evolution

Which statement best describes the evolution of pesticide resistance in a population of insects?