(D) A dependable supply of water to the Amazon basin and the deep sea has moderated the rate of extinction in both habitats.

(E) The rate of speciation in the Amazon basin is equivalent to the rate of speciation in the deep sea.

16.The author of the passage would most likely agree with which one of the following statements about Haffer's hypothesis?

(A) It provides an intriguing and complete explanation for the high rate of species diversity in the Amazon basin.

(8) It is partially correct in that a number of climatic disturbances account for species diversity in the Amazon basin.

(C) 1t has not yet been verified, but it has had an influential effect on current research on species diversity in the Amazon basin.

(D) It is better than Sanders' theory in accounting for the low rate of species extinction in the Amazon basin.

(E) It provides a compelling explanation for the distribution of species in the Amazon. basin but does not account for the high species diversity.

17. According to the passage, lowlands in the Amazon basin currently differ from uplands in which one of the following respects?

(A) Lowlands are desertlike, whereas uplands are lush.

(B) Lowlands are less vulnerable to glaciation during the ice ages than are uplands.

(C) Uplands support a greater diversity of species than do lowlands.

(D) Uplands are wetter than are lowlands.

(E) Uplands are more densely populated than are lowlands.

18. Which one of the following best describes the organization of the passage?

(A) A hypothesis is discussed, evidence that undercuts that hypothesis is presented and a new hypothesis that may account for the evidence is described.

(B) A recently observed phenomenon is described, an explanation for that phenomenon is discussed, and the explanation is evaluated in light of previous research findings.

(C) Several hypotheses that may account for a puzzling phenomenon are described and discounted. and a more promising hypothesis is presented

(D) A hypothesis and the assumptions on which it is based are described. and evidence is provided to suggest that the hypothesis is only partially correct.

(E) Two alternative explanations for a phenomenon are presented and compared. and experiments designed to test each theory are described.

19. The author of the passage mentions the number of ice ages in the third paragraph most probably in order to

(A) provide proof that cooler and drier temperatures are primarily responsible for the distribution of species in the Amazon

(B) explain how populations of species were protected from extinction in the Amazon basin

(C) explain how most existing species were able to survive periodic climatic disturbances in the Amazon basin

(D) suggest that certain kinds of climatic disturbances cause more species diversity than do other kinds of climatic disturbances

(E) suggest that geographic isolation may have occurred often enough to cause high species diversity in the Amazon basin

20. The passage suggests that which one of the following is true of Sanders' hypothesis?

(A) He underestimated the effects of winter and glaciation in the Amazon basin on the tropical rain forest.

(B) He failed to recognize the similarity in physical conditions of the Amazon lowlands and the Amazon uplands.

(C) He failed to take into a count the relatively high rate of extinction during the ice ages in the Amazon basin.

(Dl He overestimated the length of time that species have survived in the Amazon basin.

(E) He failed to account for the distribution of species in the Amazon basin.

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