1. NATURAL SELECTION

2. Darwin observed that – organisms produce more offspring than the environment can support – organisms vary in many characteristics – these variations can be inherited 13.4 Darwin proposed natural selection as the mechanism of evolution DARWIN’S THEORY AND THE MODERN SYNTHESIS

3. *Evolution- Change over time. **Natural Selection- “Survival of the Fittest” A) All species have variety in their population. B) The individuals that have the trait that best allows them to survive will live. C) Individuals with less successful traits will die. (Especially in hard times) D) Individuals that survive will reproduce and pass on the superior trait to their offspring.

4. Adaptation- physical or behavioral trait that enables an organisms to survive. -What adaptations do tigers have? Fitness- the ability of an organism to successfully pass on its genes (reproduce). - Many good adaptations = high fitness

5. Darwin concluded that individuals best suited for a particular environment are more likely to survive and reproduce than those less well adapted Darwin saw natural selection as the basic mechanism of evolution –As a result, the proportion of individuals with favorable characteristics increases –Populations gradually change in response to the environment

6. Darwin also saw that when humans choose organisms with specific characteristics as breeding stock, they are performing the role of the environment –This is called artificial selection –Example of artificial selection in plants: five vegetables derived from wild mustard Figure 13.4A

7. – Example of artificial selection in animals: dog breeding Figure 13.4B German shepherdYorkshire terrier English springer spaniel Mini-dachshundGolden retriever Hundreds to thousands of years of breeding (artificial selection) Ancestral dog

8. These five canine species evolved from a common ancestor through natural selection Figure 13.4C African wild dog CoyoteFoxWolfJackal Thousands to millions of years of natural selection Ancestral canine

9. Natural Selections / Survival of the Fittest The concept developed by Charles Darwin that genes which produce characteristics that are more favorable in a particular environment will be more abundant in the next generation. Natural selection is the process in which some organisms live and reproduce and others die before reproducing. Some life forms survive and reproduce because they are better suited to environmental pressures, ensuring that their genes are perpetuated in the gene pool

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11. Evolutionary adaptations have been observed in populations of birds, insects, and many other organisms – Example: camouflage adaptations of mantids that live in different environments 13.5 Connection: Scientists can observe natural selection in action Figure 13.5A

12. The evolution of insecticide resistance is an example of natural selection in action Figure 13.5B Chromosome with gene conferring resistance to insecticide Additional applications of the same insecticide will be less effective, and the frequency of resistant insects in the population will grow Survivor Insecticide application

13. Natural selection results in the accumulation of traits that adapt a population to its environment – If the environment should change, natural selection would favor traits adapted to the new conditions 13.12 Adaptive change results when natural selection upsets genetic equilibrium