Biology 8th Edition by Kenneth Mason ,Jonathan Losos,Susan Singer,Peter Raven,George Johnson

Exercise 6

From the chapter on evolution of development it would seem that the generation of new developmental patterns would be fairly easy and fast, leading to the ability of organisms to adapt quickly to environmental changes. Construct an explanation for why it can take millions of years, typically, for many of the traits examined to evolve. (Hint: Consider the differences in Eda allele frequency in marine and freshwater threespine stickleback fish.)