[填空题]
Mesocosms were used to study the response of freshwater sna1k 7 axvy6 ybh:vch1f+ils and alc bno/u f(wcm/h-p(m2gae to warming in two different systems,pfo2( /cm ub( mw/-nch one with fish present and one without fish. Each mesocosm had the following added to it: two different species of snails Bellamya sp. and Radix sp., and the same (one) species of phytoplankton. The snails feed on 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 at environmental temperature and F is the control with fish at environmental temperature. W is the mesocosm at increased (+4.5 °C) temperature without fish, and WF is the mesocosm at increased temperature with fish. The temperature increase of +4.5 °C was chosen to simulate the possible environmental warming that could happen in this region by the end of the century.
1.State two other variables, other than those given, that need to be controlled in the mesocosms.2
The following graphs show the fluctuations in the density of the two snails against the period of time (x axis) the study took place, along with the treatments.
(C - control, W - warming , F - with fish , WF - warming with fish)
2.Draw a line in graph A to show the peak density value for both the control (C) and warming (W) for the snail Bellamya sp., as shown in graph B for the snail Radix sp.
3.Compare and contrast the effects of warming on each species of snails in the mesocosms (W and WF).
4.State which is the preferred snail for consumption by the fish.
The preferred snail for consumption by the fish is the .
5.Predict the effect of warming in the presence of fish on the biodiversity (of snails) in open ecosystems.
6.The density of phytoplankton, shown in the graph above, was seen to vary in the presence of the fish. Suggest a reason for the increase in phytoplankton density shown in the warmer mesocosm containing fish.
7.Mesocosms have been used to simulate conditions for climate change and other studies. Outline an advantage and a disadvantage of using mesocosms to carry out these investigations.
