Microevolution is a change in gene frequency in a population. Suppose you sample a beetle population this year, 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. You have detected a microevolutionary pattern: a change in gene frequency. A change in gene frequency over time means that the population has evolved.
Image use policy: For non-commercial, educational purposes, this image may be used with a Creative Commons CC BY-NC-SA 4.0 license. Please credit as follows: © University of California Museum of Paleontology, Understanding Evolution, www.understandingevolution.org