GRE Reading Comprehension

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Source: BOOST

While it is true that living organisms are profoundly affected by their environment, it is equally important to remember that many organisms are also capable of altering their habitat significantly, sometimes limiting their own growth. The influence of the biological component of an ecosystem is often greater in fresh waters than that in marine or terrestrial systems, because of the small size of many freshwater bodies. Many of the important effects of organisms are related to their physiology, especially growth and respiration. By their growth many species can deplete essential nutrients within the system, thus Limiting their own growth or that of other species. Lund has demonstrated that in Lake Windermere the alga Asterionella is unable to grow in conditions that it itself has created. Once a year, in the spring, this plant starts to grow rapidly in the lake, using up so much silica from the water that by late spring there is no longer enough to maintain its own growth. The population decreases dramatically as a result.

Question List: 1 2 3 4

The primary topic of the passage is the way in which

  • A organisms are affected by the amount of nutrients available
  • B organisms can change their own surroundings
  • C elements of freshwater habitats impede the growth of small organisms
  • D the reproduction of organisms is controlled by factors in the environment
  • E plant matter in a given locale can increase up to a limit

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