Interaction & Interdependence C.8 Populations & Communities (id: e4a01106d)

本题目来源于试卷: Interaction & Interdependence C.8 Populations & Communities，类别为 IB生物学

[问答题]
Two different mesocosfv4h,te iu;0as / 1gym m; )fsu8-;gr osoj3jy4iv3rg nf*-qa ms were used for a study to understand the population dynamics of two ecosystems, one without fish (C ) and one with 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, prs3u;gv -3qomg4yn;*i)j8-fj o sa f rreyed 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.

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