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Item ID019016: Changes in a population in a food web (large fish) can affect the population of its prey (tadpoles).

The diagram below shows the feeding relationships between populations of plants and animals in and around a pond. The arrows point from the organisms being eaten to the organisms that eat them.

More people than usual go fishing at the pond this year and take a lot of the large fish out of the pond. Using only the relationships between the plants and animals shown in the diagram, which of the following could happen and why?

  1. The number of tadpoles is likely to increase because there are fewer large fish to eat the tadpoles.
  2. The number of large birds is likely to stay the same because large fish and large birds are not connected by an arrow in the diagram.
  3. The number of small fish is likely to decrease because with fewer large fish for the large birds to eat, the large birds would have to eat more small fish.
  4. Only the number of large fish is likely to change because only large fish were taken out of the pond.
Distribution of Responses
Chart showing distrubtion of responses for Item IE019016
Students Responding Correctly
Group Correct Total Percent
Overall 903 1399 65%
  6–8 480 790 61%
  9–12 421 607 69%
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