2019年6月15日托福阅读真题+题目+答案：Species Competition

2019年6月15日托福阅读真题+题目+答案：Species Competition

Interspecific competition occurs when two or more species seek the same limited resource. In the 1930s, Russian biologist G. F. Gause devised a set of elegant laboratory experiments that provide the basis for our formal understanding of competition. Gause grew two different species of the single-celled Paramecium—P.aurelia and P. caudatum - -separately and together. Populations of both species always increased more rapidly when they were grown alone. When grown together, populations of both species grew more slowly. ⬛Eventually, P. aurelia totally displaced P. caudatum . ⬛The results of his experiments with Paramecium species, along with similar experiments he performed on other organisms, led Gause to form this postulate: two species that directly compete for essential resources cannot coexist; one species will eventually displace the other. ⬛This postulate has come to be known as the competitive exclusion principle.

1.According to paragraph 1, which of the following statements about Gause's experiments with Paramecium is true?

O They were all conducted using various Paramecium species together.

O They were all performed in a laboratory setting.

O They were designed to test the already accepted principle of competitive exdusion.

O They proved that species that grow slowly will not displace each other.

An acre of tropical forest may include over 100 species of trees, all of which depend on the same soil, water, and nutrients. Freshwater lakes may have dozens of species of fish, all of which feed on the planktonic algae and animals suspended in the water. Indeed, two or more species of Paramecium may be found in the same lake. These and many other examples from ecological communities in nature seem to contradict Gause's principle. If two competing species cannot coexist in the laboratory, how are they able to coexist in natural settings? This question has been the basis for hundreds of ecological studies.

2.The author notes that numerous species of trees all "depend on the same soil1" and multiple species offish all " feed on the planktonic algae and animals suspended in the water" in lakes in order to

O provide examples of species that seem to contradict the competitive exclusion principle in natural settings

O point out a way in which these species coexist more easily than Paramecium species do

O draw a contrast between the resources available to fish and those on which trees depend

O indicate that one of each of these species will eventually displace all of the others it competes with

Ecologist G. Evelyn Hutchinson provided one of the most important explanations for the coexistence of competing organisms. He proposed that each species has a fundamental niche , the complete range of environmental conditions, such as requirements for temperature, food, and water, over which the species might possibly exist. Hutchinson noted, however, that few species actually grow and reproduce in all parts of this theoretical range. Rather, species usually exist only where they are able to compete effectively against other species. Hutchinson used the term realized niche to describe the range of conditions where a species actually occurs given the constraints of competition. Species whose fundamental niches overlap significantly are potential competitors. Hutchinson suggested that these potential competitors are able to coexist because they divide up the fundamental niche. Hutchinson called this division of resources niche differentiation.

3.The word "constraints" in the passage is closest in meaning to

O variations

O results

O limitations

O influences

4.What can be inferred from paragraph 3 about organisms and their fundamental niches?

O Most species live in certain parts of their fundamental niche but not in all of it.

O Competing species that share a fundamental niche eventually displace one another.

O Most species compete effectively by growing in one part of their fundamental niche but reproducing in another.

O Most species have multiple fundamental niches.

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