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Unit 8: Natural Selection (1) Genetic Variation & Diversity • There must be variety / diversity for evolution. • Genetic Variation / Diversity Individuals in a population have all inherited a unique combination of traits, giving each unique skills/strengths/weaknesses/appearances. • Genetic Variation allows for some individuals to succeed during “rough times” / changes AND THIS ALLOWS THE POPULATION TO SURVIVE! (2) What About Mutations? • Organisms CANNOT mutate whole, fully functioning body parts. • Organisms can pass on small body mutations, over thousands of years, leading to the development of a new body part. • Mutations can either hurt, or provide an advantage to individuals during times of change. – Both = Evolution (3) What is Natural Selection? • As the environment changes, certain characteristics amongst living things will help them to survive (Survival of the Fittest). • If you don’t have these characteristics, you will most likely die. • Example: The Flu – 1000’s of people die each year from the flu. – Those with a strong enough immune system live. – Those who have weak immunity, die. (4) Struggle for Existence • Living things are always competing to stay alive AND pass on their genes: – Limited food – Limited water – Limited shelter – Changes in climate, disease transmission, etc. • Those who can survive and reproduce during tough times are best suited/adapted to their environment. (5) What does it mean to Adapt? • Evolutionary Adaptation: Having the traits necessary to remain living and sexually attractive during times of change. • It does NOT mean: To change/grow body parts so that you can (6) The End Result of Natural Selection • There will be a change in the allele frequencies in the population. • Example: – Start with a population of large lizards. – Decrease in climate oxygen and available food + water. – Larger lizards do not survive during the change. – End with a population of smaller lizards. Now Let’s Watch This Video… Natural Selection video Hummingbirds YouTube Video