- 2017年12月07日16:59 来源：小站整理
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Many prehistoric people subsisted as hunters and gatherers. Undoubtedly, game animals,
including some very large species, provided major components of human diets. An important
controversy centering on the question of human effects on prehistoric wildlife concerns the sudden
disappearance of so many species of large animals at or near the end of the Pleistocene epoch.
Most paleontologists suspect that abrupt changes in climate led to the mass extinctions. Others,
however, have concluded that prehistoric people drove many of those species to extinction
through overhunting. In their "Pleistocene overkill hypothesis," they cite what seems to be a
remarkable coincidence between the arrival of prehistoric peoples in North and South America
and the time during which mammoths, giant ground sloths, the giant bison, and numerous other
large mammals became extinct.
Perhaps the human species was driving others to extinction long before the dawn of history.
Hunter-gatherers may have contributed to Pleistocene extinctions in more indirect ways. Besides
overhunting, at least three other kinds of effects have been suggested: direct competition,
imbalances between competing species of game animals, and early agricultural practices. Direct
competition may have brought about the demise of large carnivores such as the saber-toothed cats.
These animals simply may have been unable to compete with the increasingly sophisticated
hunting skills of Pleistocene people.
Human hunters could have caused imbalances among game animals, leading to the extinctions
of species less able to compete. When other predators such as the gray wolf prey upon large
mammals, they generally take high proportions of each year's crop of young. Some human hunters,
in contrast, tend to take the various age-groups of large animals in proportion to their actual
occurrence. If such hunters first competed with the larger predators and then replaced them, they
may have allowed more young to survive each year, gradually increasing the populations of
favored species. As these populations expanded, they in turn may have competed with other game
species for the same environmental niche, forcing the less hunted species into extinction. This
theory, suggests that human hunters played an indirect role in Pleistocene extinctions by hunting
one species more than another.
1. What does the passage mainly discuss?
(A) The effects of human activities on prehistoric wildlife
(B) The origins of the hunter-gatherer way of life
(C) The diets of large animals of the Pleistocene epoch
(D) The change in climate at the end of the Pleistocene epoch
2. The word "Undoubtedly" in line 1 is closest in meaning to
3. The word "components" in line 2 is closest in meaning to
4. Which of the following is mentioned as supporting the Pleistocene overkill hypothesis?
(A) Many of the animals that became extinct were quite large.
(B) Humans migrated into certain regions around the time that major extinctions occurred.
(C) There is evidence that new species were arriving in areas inhabited by humans.
(D) Humans began to keep and care for certain animals.
5. The word "Besides" in line 14 is closest in meaning to
(A) caused by
(C) in addition to
(D) in favor of
6. The author mentions saber-toothed cats in line 17 as an example of a carnivore that
(A) became extinct before the Pleistocene epoch
(B) was unusually large for its time
(C) was not able to compete with humans
(D) caused the extinction of several species
7. The word "they" in line 22 refers to
(A) human hunters
(B) game animals
(C) other predators
(D) large mammals
8. According to the passage , what is one difference between the hunting done by some humans
and the hunting done by gray wolves?
(A) Some humans hunt more frequently than gray wolves.
(B) Gray wolves hunt in larger groups than some humans.
(C) Some humans can hunt larger animals than gray wolves can hunt.
(D) Some humans prey on animals of all ages, but gray wolves concentrate their efforts on young
9. The word "favored" in line 26 is closest in meaning to
10.According to the passage , the imbalances discussed in paragraph 3 may have resulted from
(A) the effect of climate changes on large game animals
(B) large animals moving into a new environment
(C) humans hunting some species more than others
(D) older animals not being able to compete with younger animals