Theory of Natural Selection Power Notes Mrs. Riordan What is your definition of Evolution? The slow change in organisms that occurs over many generations. Natural Selection is: The process by which organisms change over time, as those best suited to their environment survive to pass on their genes to the next generation. Population: All Members of a species living in a given area at a given time. Key insights that led Darwin to the theory of evolution: Artificial selection- Darwin noticed a lot of variation of traits in domesticated animals and plants. Humans can increase the chances of certain traits being passed down. Heritability – Natural Selection can only act on traits that already exist. Traits must be heritable in order to be passed down Struggle for survival – There is only so much food and resources available so only the most “fit” survive. 4 main principles of natural selection Principle Sexual 1: Variation: reproduction and mutations contribute to variation within a gene pool. Principle 2: Overproduction Individuals tend to produce more offspring than the environment can support. (over-population / competition). Principle 3 : Adaptation An adaptation is a change in an individual in order to fill a niche or survive in its environment. Adaptations add up over time to drive Natural Selection. Principle 4: Inheritance of traits Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring than those individuals less suited to the environment (Inheritable characteristics). Fitness Is a measure of survivability and the ability to produce offspring Survival of the Fittest Another word for natural selection. Organisms that are best adapted to the environment survive to pass on their genes to the next generation.