PCB 6466: Homework 7 DUE TUE Oct 20 1. A classical, agricultural experiment (the yields.txt data set) grew a variety of wheat with the same fertilizer amounts and water, but in three different soils, where randomlyselected fields were in either sandy, clay, or loam soils. Did soil type significantly affect wheat yield (bushels/acre)? If so, which treatments differed from which other treatments and by how much, on average? 2. Tannins are a complex mix of organic compounds produced by plants. One hypothesis is that they are just waste products. Another is that they combat predators, such as caterpillars. An experiment was conducted by feeding artificial diets dosed with different levels of tannins to caterpillars raised under the same conditions (tannins.txt). The experiment did not have replicates of each tannin level but did have a control. The hypothesis was that more tannin led to less caterpillar growth. Was the hypothesis supported? If so, how much effect did tannin have on growth? 3. Some plant extracts may be anti-cancer agents (or may have no real effect). An experiment was conducted with 3 plant extracts (Drugs A, B, & C) and controls (the same drug that would be used as a placebo. Cultures of cancer cells were dosed with the same concentrations of all drugs and then the percent of dead cells was counted (cancer.txt). Did plant extracts cause significant cancer cell death? If so, which treatment worked best? 4. Competition by exotic species may inhibit success of threatened species. An experiment (competition.txt) first heat-treated soils to kill most seeds, then mixed the soil and seeded random plots with a threatened species by itself (solo), or together with one of three exotic species. All plots had the same initial total number of seeds. At the end of the growing season the biomass (dry weight) of the threatened species was measured. Did exotic species significantly inhibit growth of the threatened species? If so, how would you rank the exotics for their inhibitory effect on the threatened species?