Biological clocks. Many plants and animals have "biological clocks" that coordinate activities with the time of day. When researchers looked at the length of the biological cycle in the plant Arabidopsis by measuring leaf movements, they found that the length of the cycle is not always 24 hours. Further study discovered that cycle length changes systematically with north-south location. Table 3.3 contains cycle lengths for 149 locations around the world.39 Describe the distribution of cycle lengths with a histogram and numerical summaries. In particular, how much variation is there among locations?
