Biology Notes Biology: Dr. Hensley / Mrs. Ingram 2016 Genetic Equilibrium – Allele frequencies remain constant. (this doesn’t really happen in nature, just used as a comparison to see how populations change. Hardy-Weinberg Equilibrium – There will be genetic equilibrium if of the following conditions are true: ALL Random Mating Large Population No Migration (leaving an area) and No Immigration (entering an area) No Mutations No Natural Selection Species – Organisms that can reproduce and produce fertile offspring. Speciation – Making new species Reproductive Isolation - Preventing species that could mate from doing Caused by the following: so. Behavioral – When behavior changes (usually in animals) causing absence of mating. Example: Mating songs changed between the Eastern and Western Meadowlark preventing mating from taking place. Geographic – Physical barrier comes between individuals and preventing mating such as mountains, oceans, rivers, canyons, etc. Temporal – When timing is off for mating such as the season (spring, summer, fall, winter) or time of day (daytime, night time) the organisms like to mate.