AP Environmental Science FRQ Question 1 (Set 2)

Answer the questions. Where calculations are required, clearly show how you arrived at your answer. Where explanation or discussion is required, support your answers with relevant information and/or specific examples.

Soil erosion is one of the most serious soil-degrading processes. Each year tons of soil erode from cropland, pastures, forests, and other places.  The amount of erosion varies dramatically among various land-use types. The figure above shows the effects of different agricultural practices and slopes on annual erosion rates. Refer to the graph above for the following.

Identify the scientific question that resulted in the data presented in the first graph.

Identify the agricultural practice that could be used on a 15% slope without leading to a higher than tolerable loss of soil.

Describe the effect of adding a cover crop compared to using the no-till method.

Identify one natural mechanism of soil erosion.

Sediment from erosion can enter streams and affect water quality.  One way sediment can enter a stream is from nearby road construction.  Two methods to reduce sediment run-off in streams are to either put down straw bales or plant grass.  The hypothesis to be tested is that straw bales reduce more sediment run-off than planted grass does.  To test the hypothesis, two plots near a road under construction are measured.  On one plot (A), straw bales are used to cover the soil, while a second plot (B) is planted with grass.  The sediment discharge from each plot is measured after rainfall. 

(i) Identify the dependent variable stated in the hypothesis. 

(ii) Describe one way to add a control to improve the design of the study. 

(iii) Identify one variable that was not discussed that could affect the results of the study. Sediments reaching streams affect water clarity, which is tested by determining turbidity.  Turbidity can be determined by measuring the depth at which a submerged object can no longer be seen from the surface. 

(iv) Based on the data in the table above, make a claim about the stated hypothesis. 

(c) Several fish species lay their eggs in the gravel in the streams under investigation in the study. 

(i) Describe the type of survivorship curve expected for these fish species. 

(ii) Explain why the input of sediment to a stream can negatively affect reproduction of fish that lay their eggs in the gravel of the streambed.