Natural Variation Even within a species individuals vary from each other Discussion Question These are the same species of moth. The two are naturally occurring variations. Describe situations where the coloration would be an advantage for the moth. How We Use Variation Artificial selection nature provides the variation and humans select the variations they find useful Evolution by Natural Selection Natural Selection the traits being selected (which therefore increase over time) contribute to an organisms fitness in its environment Natural Selection The struggle for existence Survival of the fittest Descent with modification Struggle for Existence Members of each species compete regularly to obtain food, living space, and other necessities of life Run fast, behavioral tactics, camouflage Survival of the Fittest Individuals better designed for the environment where they live will survive and reproduce most successfully Fitness is the result of successful adaptations Survival of the Fittest Fitness the ability to survive and reproduce in a specific environment Adaptation an inherited characteristic that increases an organisms chance of survival Discussion Question Give three examples of animals with designs that help their survival. Tale of the Peacock Online Video Clip ators/course/session4/explain_a.htmlators/course/session4/explain_a.html Or: Why Sex? (PBS Evolution Series) minutes 17:00 28:00 KEY CONCEPT Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness in its environment. Common Descent Evidence for Evolution 1) Fossil record 2) Animals with similar selection pressures evolve similar features 3) Homologous structures 4) Similarities in early development Genetic Toolkit Online Video Clip ators/course/session4/engage_a.htmlators/course/session4/engage_a.html (5 min) similar habitats & similar structures homologous structures similarities in embryology