Biology Class ONline Evolution Variation of traits in a population is often controlled by genes. Therefore, changes in the genes cause changes in the corressponding traits. Genetic equilibrium is the condition in which allele frequencies in a population do not change from generation to generation. Many populations stay in genetic equlibrium for generations but eventually a population will fall out of genetic equilibrium and that is evolution will occur. Click on genetic equilibrium to learn about the changes in genetic equilibrium that lead to evolution.
Natural selection cause the most significant genetic changes in a population.
However, these changes do not always lead to speciation - the formation of new species. Click on speciation to find out how it occurs. An inherited variation that increases an organism's chance for survival in a particular environment is called an adaptation. An adaptation could spread throughout the entire species over many generations. In this way, according to Darwin, evolution by natural selection would occur.