It is now thought that the atmosphere of the primitive Earth was composed largely of carbon dioxide, nitrogen, and water vapor. The composition of certain iron-containing minerals suggests that the carbon dioxide began to be replaced by oxygen about 2 billion years ago.   Which of the following is the best explanation for the change in atmospheric composition?

#Question id: 4647

#Unit 11. Evolution and Behavior

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?

#Question id: 4648

#Unit 11. Evolution and Behavior

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?

#Question id: 4649

#Unit 11. Evolution and Behavior

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

#Question id: 4650

#Unit 11. Evolution and Behavior

DDT was once considered a ʺsilver bulletʺ that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

#Question id: 4651

#Unit 11. Evolution and Behavior

Some members of a photosynthetic plant species are genetically resistant to an herbicide, while other members of the same species are not resistant to the herbicide. Which combination of events should cause the most effective replacement of the non-herbicide-resistant strain of plants by the resistant strain?

1. The presence of the herbicide in the environment

2. The absence of the herbicide from the environment

3. The maintenance of the proper conditions for one generation

4. The maintenance of the proper conditions for many generations

#Question id: 4652

#Unit 11. Evolution and Behavior

The graph depicts four possible patterns for the abundance of 3TC-resistant HIV within an infected human over time. If 3TC resistance is costly for HIV, then which plot (I—IV) best represents the response of a strain of 3TC-resistant HIV over time, if 3TC administration begins at the time indicated by the arrow?