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Natural Selection EQ: How does natural selection lead to evolution? 1. What was Darwin’s reasoning? 1. Plants and animals that arrived on the Galapagos faced environmental factors that were different from the mainland. 2. Species gradually changed over many generations and became better adapted to the new environment. 2. What is evolution? • The gradual change in a species over a long period of time 3. What is a species? • A group of similar organisms that can mate and produce fertile offspring. 4. What is selective breeding? • The practice by which humans select plants or animals for breeding based on desired traits. • Ex: dogs If we could achieve these differences in a few hundred years, what is possible in millions of years? 5. What is natural selection? • The process in which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. • Also known as “survival of the fittest” 6. What factors affect the process of natural selection? 1. Overproduction: (more organisms are born than will survive) 2. Variation: (each individual has its own unique set of traits; similar but not the same) 6. What factors affect the process of natural selection? 3. Competition [or Struggle to survive] (species compete for food, space, and other resources) 4. Selection (organisms that are best suited to their environment will survive) 6. What factors affect the process of natural selection? 5. Survival and Successful Reproduction ( the survivors reproduce and pass along their beneficial traits) 7. Can natural selection lead to change? • YES! Over a long period of time natural selection can lead to change. • Helpful variations increase while harmful variations decrease. • Nature “selects” characteristics. 8. What are environmental factors? • Things in the environment that can affect an organism’s ability to survive. • Ex: predators and food supply 9. What about genetic variation? • Individuals need to be different for natural selection to work, otherwise, all individuals would have an equal chance of survival! • Only traits that are inherited, or controlled by genes, can be acted upon by natural selection. 1. Overproduction • organisms produce more offspring than can survive. • Ex: too many sea turtles! 2. Variation • Each individual has its own unique combination of traits. Similar but not identical. • Ex: some turtles are faster than others 3. Competition (Struggle to Survive) • Some may get caught by predators or starve or get disease. Only some make it to adulthood. • Ex: not enough food + predators 4. Selection • Turtles that are best adapted to their environment are likely to have many offspring that survive. 11. Example of natural selection: • Peppered moth variation: black form and white form environment: trees in England