Explain5 marksChallenge
In a population of snails, shell banding pattern is a discontinuous character: shells are either banded or unbanded. A survey recorded 320 banded and 80 unbanded individuals.
A student also measured shell width (a continuous character) in 30 banded snails and 30 unbanded snails. The mean shell width of banded snails was 14.2 mm with a standard deviation of 1.1 mm; the mean for unbanded snails was 13.5 mm with a standard deviation of 1.0 mm.
Explain how the genetic basis of discontinuous variation (such as shell banding) differs from that of continuous variation (such as shell width). In your answer, discuss the role of environmental factors and describe how a t-test could be used to compare the mean shell widths of the two groups.