[问答题]
Two different mesocos
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a6fhqf.e5v )nh fish (F). Each mesocosm had the following added to it: two different species of snails and the same (one) species of phytoplankton. The snails feed on the phytoplankton and are, in turn, preyed upon by the fish.
The following diagrams show the mesocosms used for the study. C is the control without fish, and F is the experimental mesocosm with one fish added. Both mesocosms were maintained at the same temperature and light conditions.
After a period of time, as shown in the graph below, the density of phytoplankton was seen to vary in the two mesocosms used in the study.
1.Outline a reason for the variation seen in the density of the phytoplankton in the two mesocosms, as shown above.
2.Explain whether this is indicative of a top-down or bottom–up control of the simulated ecosystem.
