Microevolution is evolution on a small scale within a single population. That means narrowing our focus to one branch of the tree of life. One area at a time.
Imagine that you go to the mountaintop this year, sample these beetles, and determine that 80% of the genes in the population are for green coloration and 20% of them are for brown coloration. You go back the next year, repeat the procedure, and find a new ratio: 60% green genes to 40% brown genes.
