Other important evolution theory and facts….

Darwin’s theory of gradualism.. Darwin believed that seldom are their drastic changes in species from one generation to the next, but they are usually small continuous changes that accumulate over thousands of years. Population gradualism says that new traits happen by increasing their frequency through generations. Initially the trait is a only in a small fraction of a population and then over time it becomes a frequent trait.

Gradualism continued.. Phenotypic gradualism – New traits ONLY evolve in small incremental steps. This is still VERY controversial. Punctuated Equilibrium – Contradicts the above theory. It says there are large changes over small periods, followed by long periods of no change.

Adaptations Adaptations: All developmental, physiological, anatomical and behavioral changes to help organisms survive and reproduce in their environments.

Polar Bear Physical Adaptations Polar Bears can survive in temperatures as low as -150 degrees F. Two layers of fur provide the bears with such good insulation that they experience almost no heat loss. In addition, they are protected with a layer of blubber that can measure 11.5 cm (4.5 inches) thick. Compact ears and a small tail also prevent heat loss. Other adaptations include small bumps called papillae that keep their feet from slipping on ice; strong, powerful claws that enable them to catch seals; and a nose powerful enough to detect prey that is miles away.

Polar Bear Swimming Adaptations Polar bears are strong swimmers. They can swim for several hours at a time over long distances. They've been tracked swimming continuously for 62 mi. A thick layer of blubber, up to 4.3 inches thick, keeps the polar bear warm while swimming in cold water. A polar bear's nostrils close when under water diving. They have been seen diving to depths of over 20 feet.

Behavioral Adaptations Polar Bear’s main source of food is the ringed seal. They wait at breathe holes for the seals to pop up and grab them by their head. They will cover their black nose with snow so they are more camouflaged when preying upon the seal.

Sorting…and genetic drift Sorting is the different survival and reproduction rates among various individuals. Genetic Drift is the chance fluctuation in allelic frequency from one generation to the next; or in English the chance that your parents traits or relatives traits will be passed to you and your offspring.

Relative fitness The ability of a trait (a genotype of certain gene) to survive from one generation to the next. If a genotype has a higher relative fitness it will be passed down from one generation to the next.

Macro vs. Micro Macro – Large scale events in evolutions. Drastic changes… Micro – Small scale changes that cause small changes in species.

Mass Extinctions Events, which cause large number of species to go extinct simultaneously. The causes are uncertain, perhaps huge geologic events, meteor strikes, drought, etc. Currently species are going extinct at rate over 100 greater than the last mass extinction.