Principle# 1 Genetic Variation: There are 3 types of polar bears thick coasts medium coats and thin coats. DNA originally comes from the brown polar bear 150,000 years ago. Polar bears can breed with brown bears to produce fertile grizzly polar bear.
Principle# 2 Overpopulation & selective pressures: Due to temperatures are dropping rapidly and the polar bears must be kept warm or they will die.
Principle# 3 Differential Survival & Reproduction: Polar bears couples are only together for a week after they separate. The male may then seek out another mate. Males find other females by scent.
Principle # 4 Changes in the Gene Pool: Due to extreme temperature mother polar bears only have one cub left and Thin coats are being selected and thick coats are the better trait.