- Some Animals Are More Equal Than Others Trophic Cascades And Keystone Species Mean Leaf Area Per Plant Over 18 Months W 1 (35.49 KiB) Viewed 42 times
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Some Animals Are More Equal than Others: Trophic Cascades and Keystone Species Mean Leaf Area per Plant Over 18 Months without beetle with beetle Leaf Area per Plant (cm²) 2400 2200 2000 1800 1600 1400 1200 1000 800 02 T 6 T 8 10 12 14 Months After Start of Experiment 4 T 16 18 Refer to the figure to answer questions 12 through 17. Student Handout Figure 2. Mean leaf area per tree. Initial measurements were taken before (0 to 2 months) and after (7 to 18 months) beetles were added to 40 of 80 plants. The light gray round markers represent measurements taken of the control plots, to which beetles were not added. The black square markers represent measurements taken of the experimental plots, to which beetles were added. Measurements were made on all leaves to calculate the mean leaf area per plant. Error bars represent standard error of the mean.
Some Animals Are More Equal than Others: Trophic Cascades and Keystone Species 15. Describe the impact of adding the beetles on each species in the food chain above. Student Handout 16. Which statement do Letourneau and Dyer's results support? a. Adding beetles reduced ant numbers and triggered a trophic cascade that increased the mean leaf area left on plants. b. Adding beetles had little effect on this ecosystem, showing that it is primarily regulated from the bottom up. c. Adding beetles reduced ant numbers and triggered a trophic cascade that decreased the mean leaf area left on plants. d. Adding beetles reduced ant numbers and increased the caterpillar population size, proving that the caterpillars are a keystone species in this habitat. 17. Do the results of the Letourneau and Dyer experiment support or refute the green world hypothesis? Explain your answer.
14. Draw two diagrams that show the food chains for both the experimental and control plots. Include interactions among predatory beetles (if present), ants, caterpillars, and piper plants. Control Experimental