1. Mechanisms of Evolution How does this all work?

3.  The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)  Charles Darwin (1809-1882) saw three problems in need of a solution.

4. The First Problem  There is change over time in the flora and fauna of the Earth

5. The Second Problem  There is a taxonomic relationship among living things

6. The Third Problem  Adaptation

7. The Solution! Processes that drive evolution  1. Natural Selection  2. Gene Flow  3. Sexual Selection  4. Mutation

8. 1. Natural Selection  * Survival of the fittest.......  What is Fitness ? What is Fitness Physical traits and behaviors that enable organisms to survive and reproduce in their environment

9. How ’ s it work?  1. OVERPRODUCTION  More are born or hatched or whatever, than survive and reproduce

10. How ’ s it work? 2. VARIATION This variation can be inherited Remember, there was NO genetics back then, Chuck knew, he just knew…. Realized that is wasn’t ‘blending

11. How ’ s it Work?  3. Selection Determines which individuals enter the adult breeding population  This selection is done by the environment  Those which are best suited reproduce  They pass these well suited characteristics on to their young

12. How it works?  4. Adaptation * Over time – those traits that improve fitness will become more common.

13. How ’ s it Work?  REPRODUCTION is the key, not merely survival  If you survive to be 128 but have no kids, you are not doing as well as I am  I have reproduced…  Assuming the traits that made me successful will help my kids then I am more fit NOW than the 127 year old guy

14. This lecture keeps evolving …..  So, the answer to the trilogy of problems is:  ‘Descent with modification from a common ancestor, NOT random modification, BUT, modification shaped by natural selection’

15. The Origin of Species How did Darwin say it? “As many more individuals of each species is born than can possibly survive, and consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance for survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”

16. One Year Many Years… 1 2

17. 2. Gene Flow also called migration— is any movement of genes from one population to another.

18. 3. Sexual Selection

19. = random, heritable changes in DNA sequences that introduce new alleles into a gene pool 4. Mutation