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(A) the overwintering generation forms two sets of eggs, one exposed to the colder temperatures of winter and one exposed only to the warmer temperatures of spring
(B) the eggs that produce micropterous and macropterous adults are morphologically different
(C) water bugs respond to seasonal changes by making an acclimatory functional adjustment in the wings
(D) water bugs hatching in the spring live out their life spans in ponds and never need to fly
(E) the overwintering generation, which produces eggs developing into the dimorphic generation, spends the winter in the forest and the spring in small ponds
18. It can be inferred from the passage that which one of the following is an example of a regulatory response?
(A) thickening of the plumage of some birds in the autumn
(B) increase in pulse ate during vigorous exercise
(C) gradual darkening of the skin after exposure to sunlight
(D) gradual enlargement of muscles as a result of weight lifting
(E) development of a heavy fat layer in bears before hibernation
19. According to the passage, the generation of water bugs hatching during the summer is likely to
(A) be made up of equal numbers of macropterous and micropterous individuals
(B) lay its eggs during the winter in order to expose them to cold
(C) show a marked inability to fly from one pond to another
(D) exhibit genetically determined differences in wing form from the early spring-hatched generation
(E) contain a much greater proportion of macropterous water bugs than the early spring-hatched generation
20. The author mentions laboratory experiments with adult water bugs (lines 63-66) in order to illustrate which one of the following?
(A) the function of the summer generation’s dimorphism
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