1. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Lectures by Chris C. Romero PowerPoint ® Lectures for Essential Biology, Third Edition – Neil Campbell, Jane Reece, and Eric Simon Essential Biology with Physiology, Second Edition – Neil Campbell, Jane Reece, and Eric Simon CHAPTER 13 How Populations Evolve

5. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings EVOLUTION - a change over time in the genetic composition of a population driven by natural selection. The basic idea of natural selection is that –Organisms can change over generations. –Individuals with certain favorable heritable traits leave more offspring than others.

6. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Evolution trends 1.Convergent evolution – unrelated species evolve in similar ways. Same environmental pressure produces similar adaptation. Exp. Animals that fly. 2.Divergent evolution – population splits into a new species to better suit their environment. 1.Allopatric speciation 2.Sympatric speciation 3.Parallel evolution – species that separated for a very long time but still evolve independently maintaining similar traits 4.Co-evolution – close interactive species (birds & flowers) exert selective pressure so they evolve together

7. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Darwin made two main points in The Origin of Species: –Organisms today came from ancestral species and natural selection was the mechanism for descent with modification.

8. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings A. Evidence 1.Fossils - remnants or impressions left by organisms that lived in the past. 2.The fossil record & sedimentary rock –The fossil record is the ordered sequence of fossils as they appear in rock layers in history.

9. Figure 13.7

10. Figure 13.8

11. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Evidence continues 3.Comparative anatomy – comparing body structure between different species. 4.Homology - similarity in structures due to common ancestry. a)Fore limbs of human, cats, whales, and baths b)Vestigial organs – structures that have no importance to a living organisms but did in the organisms’ ancestor. 5.Comparative embryology is the comparison of structures that appear during the development of different organisms.

12. Figure 13.11

13. Figure 13.12

14. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Evidence Continues 6.Molecular Biology – similarities when comparing DNA and proteins in different organisms.

15. Figure 13.13

16. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Three General Outcomes of Natural Selection 1.Directional selection – favor extreme phenotype. 2. Disruptive selection - Can lead to a balance between two or more contrasting morphs in a population. 3. Stabilizing selection - Maintains variation for a particular trait within a narrow range. 4. Sexual selection – pea cock: look good=good genes

17. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings B. Natural Selection in Action Examples of natural selection include –Pesticide resistance in insects. –The development of antibiotic-resistant bacteria. –Drug-resistant strains of HIV.

18. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings C. Sources of Genetic Variation 1.Mutations - changes in the DNA of an organism. 2.Sexual recombination - Shuffles alleles during meiosis.

19. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings D. Speciation 1.Species – a population of organisms that can interbreed (mate, reproduce) 2.Speciation – the creation of new species 1.Allopatric – new species created due to geographical isolation (mountain ranges, water, etc). 2.Sympatric – no geographic isolation but a new species is created due to random mating and changes in the chromosome set number. 1.2 sets of chromosomes to 3 sets. the 2 organisms can no longer interbreed. Most common in plants. Polyploidy.