托福阅读真题+题目+答案：Circadian and Circannian Rhythms

托福阅读真题+题目+答案：Circadian and Circannian Rhythms

Certain mammalian behaviors serve to promote the survival of the individual. One striking aspect of animal behavior is the rhythmic, or cyclic. pattern of activity. Some species are active at night (nocturnal) and some during the day (diurnal); others are active primarily at dawn and dusk. The activity periods tend to be at regular intervals. The time of emergence of a particular species of bat may differ by no more than two or three minutes night after night. Animals also exhibit other kinds of cyclic behavior. The timing of reproduction is cyclic, and in some mammals, such as some rodents and bats, daily or seasonal shifts occur between highly active and torpid states. Migratory movements are also cyclic. Daily activity rhythms, those based on a 24-hour cycle, are termed circadian rhythms and are better understood than other types of rhythms.

1.Why does the author provide the information that "The time of emergence of a particular species of bat may differ by no more than two or three minutes night after night"?

A.To support the idea that animals have very consistent activity patterns.

B.To suggest that nocturnal animals exhibit more regular activity patterns than diurnal animals do.

C.To provide an example of an animal that generally exhibits an unusual type of cyclic behavior.

D.To emphasize that nocturnal animals are almost never active during the day.

2.In paragraph 1. all of the following are mentioned as types of cyclic behavior EXCEPT

A.patterns of animal migration

B.the seasonal shift from nocturnal activity to diurnal activity

C.the time when reproduction occurs

D.changes in activity level that occur daily or seasonally

Circadian rhythms differ markedly from one species to another.Most mammals are nocturnal, but even in two nocturnal species there are contrasts between the patterns of activity. In general, small mammals that are especially vulnerable to predation, such as rodents. tend to be nocturnal. whereas less vulnerable species, such as many ungulates (mammals with hooves), may be active during the day. The activity cycles of carnivores seem to be geared to the circadian cycles of their prey or to the period when hunting is most rewarding.

3.Paragraph 2 suggests which of the following about small mammals, such as rodents, that are vulnerable to predation?

A.They are less vulnerable to predation than are ungulates.

B.Their circadian rhythm is different from the circadian rhythms of their predators.

C.Their primary predators are larger animals called ungulates.

D.They are better able to avoid predators at night than during the day.

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