Does light environment have an influence on the development of color vision? The accompanying data, from Fuller

Question:

Does light environment have an influence on the development of color vision? The accompanying data, from Fuller et al. (2010), are measurements of the relative abilities of bluefin killifish from two wild populations to detect short wavelengths of light (blue light in our own visible color spectrum). One population was from a swamp, whose tea-stained water filters out blue wavelengths, whereas the other population was from a clear-water spring. Fish were crossed and raised in the lab under two light conditions simulating those in the wild: clear and tea-stained. Sensitivity to blue light was measured as the relative expression of the SWS1 opsin gene in the eyes of the fish (as a proportion of total expression of all opsins). Opsin proteins in eyes detect light of specific wavelengths; SWS1 is so named because it is shortwave sensitive. The data are from a single individual from each of 33 families. Because the fish were raised in a common lab environment, population differences are likely to be genetically based, whereas differences between fish under different water clarity conditions are environmentally induced.

Population Water clarity SpringSpring ClearClear 0.160.16 0.110.11, 0.120.12, 0.110.11. 0.080.08. 0.090.09.

a. How many factors are included in this experiment? Identify them.

b. What type of experimental design was used?

c. Draw an interaction plot of the data.

d. Provide a word statement of a full linear model to fit to the data.

e. Examine your graph from part (c), and state which effects are likely to be present in the results. Say how you reached your conclusions. Explain whether the genetic and enviromentally induced effects on SWS1 opsin expression appear to be in the same direction.

f. The ANOVA results of the linear model analysis are shown in the table below. What null hypotheses are tested?

g. Using this table, indicate which main effects were found to be statistically significant. Do the results agree with your assessment in part (e) based on your graph?

TABLE FOR PROBLEM 17 Source PopulationPopulation Water treatment Water treatment Population *water treatment