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Question 3 A study investigated the interaction two species of mites, and how the presence of heavy metals in the soil affected their interaction. Mite Species A is herbivorous, and mite species B is carnivorous. The life span of each species is about 14 days. The researchers planted 120 food plants three meters from each other in an empty, newly-tilled field. At the start of the experiment, they placed 75 mites of each species onto each plant, for a total of 150 mites per plant. They tilled copper ions (a heavy metal) into the soil around 60 of the plants, which is taken up by plants through their roots. The treatments were as follows: Treatment 1- mite Species A and B grown together on plants, no heavy metals; Treatment 2- mite Species A and B grown together on plants, heavy metals in the soil. . All plants experienced the same precipitation, temperature, initial copper levels in the soil, relative humidity, and wind. The same concentration of copper ions were tilled into the soil around all relevant plants. The researchers monitored the abundance of each species for 120 days, sampling every 10 days.

Abundance of Two Mite Species Over Time Without Heavy Metals in Soil 120 100 80 Average Abundance (Individuals) Per Plant 40 Mite A-Mite B 20 0 10 20 30 40 50 60 70 80 90 100 110 120 Day of Sampling FIGURE 3. AVERAGE ABUNDANCES OF TWO MITE SPECIES GROWN TOGETHER IN THE ABSENCE OF COPPER IN THE SOIL

Abundance of Two Mite Species Over Time With Heavy Metals in Soil 160 2 140 3 120 100 Average Abundance (individuals) Per Plant o 8 8 8 8 7 7 7 7 3 Mite A Mite 0 10 20 30 80 90 100 110 120 40 50 60 70 Day of Sampling FIGURE 4. AVERAGE ABUNDANCES OF TWO MITE SPECIES GROWN TOGETHER IN THE PRESENCE OF COPPER IN THE SOIL

A. Identify any independent variables in this experiment. Be specific. B. Identify any dependent variables in this experiment. Be specific. C. Of the many types of interactions between organisms that you have learned about this semester, identify the specific type of biological interaction that is most likely occurring between mite Species A and mite Species B in the absence of the copper in the soil. Explain how you know this, with reference to specific data from the graphs in your answer. D. Interpret the effect of the copper on the biological interaction between mite species. You must reference specific data from the graphs in your answer. Do not just describe the data, and do not add any information that isn't in the graphs. E. Describe one realistic, potential reason for the results in Figure 4.