1. Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Thursday 5/26 ● Parts of Chapters 13 and 14

2. Evolution Evolution – genetic change in a population or a species over generations. An understanding of evolution informs every field of biology, for example: Agriculture Medicine Biotechnology Conservation biology

3. Darwin made two main points in The Origin of Species: Organisms inhabiting Earth today descended from ancestral species Natural selection was the mechanism for descent with modification Individual variation Overproduction of offspring Observations Natural selection: unequal reproductive success Conclusion Evolution

4. Observing Natural Selection There are many examples of natural selection in action. Galápagos finches change beak size depending upon the size and shape of available seeds.

5. Natural Selection in Action Examples of natural selection include: Pesticide-resistant insects Antibiotic-resistant bacteria Drug-resistant strains of HIV Chromosome with gene conferring resistance to pesticide Reproduction Survivors Insecticide application

6. Evolution Natural selection leads to: A population (a group of individuals of the same species living in the same place at the same time) changing over generations Evolutionary adaptation A Trinidad tree mantid that mimics dead leaves A flower mantid in Malaysia A leaf mantid in Costa Rica

7. Evidence of Evolution –Biological evolution leaves observable signs. –We will examine five of the many lines of evidence in support of evolution: The fossil record Biogeography Comparative anatomy Comparative embryology Molecular biology

8. The Fossil Record –Fossils are: Imprints or remains of organisms that lived in the past Often found in sedimentary rocks Evidence of Evolution

9. Biogeography Common ringtail possum Red kangaroo Common wombat Australia Koala –The study of the geographic distribution of species that first suggested to Darwin that today’s organisms evolved from ancestral forms.

10. Evidence of Evolution Comparative Anatomy Is the comparison of body structure between different species Confirms that evolution is a remodeling process HumanCatWhale Bat

11. Evidence of Evolution Comparative Embryology –Early stages of development in different animal species reveal additional homologous relationships. Post-anal tail Human embryo Chicken embryo Pharyngeal pouches Comparative Embryology

12. Evidence of Evolution Molecular Biology –The hereditary background of an organism is documented in: Its DNA The proteins encoded by the DNA –Evolutionary relationships among species can be determined by comparing: Genes Proteins of different organisms

13. Populations as the Units of Evolution –A population is: A group of individuals of the same species, living in the same place, at the same time The smallest biological unit that can evolve –Gene pool - The total collection of alleles in a population at any one time. –Microevolution - When the relative frequency of alleles changes over a number of generations, (evolution is occurring on its smallest scale).

14. Mechanisms of Evolution –The main causes of evolutionary change are: Genetic drift Gene flow Natural selection

15. –Genetic drift is: A change in the gene pool of a small population Due to chance Only 5 of 10 plants leave offspring RR rr Rr RR Rr RR Rr Only 2 of 10 plants leave offspring RR rr RR Rr rr RR Rr rr RR Mechanisms of Evolution

16. –The bottleneck effect: Is an example of genetic drift Results from a drastic reduction in population size Original population Bottlenecking event Surviving population Mechanisms of Evolution

17. –The founder effect is likely when a few individuals colonize an isolated habitat and represent genetic drift in a new colony. South America Tristan da Cunha Africa Mechanisms of Evolution

18. –Gene flow: Is genetic exchange with another population Tends to reduce genetic differences between populations Mechanisms of Evolution

19. Outcomes of Natural Selection Original population Phenotypes (fur color) Frequency of individuals (a)Directional selection (b) Disruptive selection (c) Stabilizing selection Evolved population Original population

20. ●Sexual dimorphism is: A distinction in appearance between males and females Not directly associated with reproduction or survival ●Sexual selection is a form of natural selection in which inherited characteristics determine mating preferences. Mechanisms of Evolution (a) Sexual dimorphism in a finch species (b) Competing for mates

21. Evolution Macroevolution: Encompasses the major biological changes evident in the fossil record Includes the formation of new species –Speciation: Is the focal point of macroevolution May occur based on two contrasting patterns –In nonbranching evolution: A population transforms but Does not create a new species

22. Evolution and Speciation Speciation: Is the focal point of macroevolution May occur based on two contrasting patterns In nonbranching evolution: A population transforms but Does not create a new species Branching Evolution (results in speciation) Nonbranching Evolution (no new species)

23. Biological Species Concept –Species is a Latin word meaning: “Kind” or “Appearance.” –The biological species concept defines a species as “A group of populations whose members have the potential to interbreed and produce fertile offspring”

24. Reproductive Barriers between Species Postzygotic barriers Gametes Viable, fertile offspring Zygote Prezygotic barriers Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation Gametic isolation –Prezygotic barriers prevent mating or fertilization between species. –Postzygotic barriers operate if: Interspecies mating occurs and Hybrid zygotes form

25. Mechanisms of Speciation Species can form by: Allopatric speciation, due to geographic isolation Sympatric speciation, without geographic isolation Allopatric speciation Simpatric speciation

26. Geographic barrier Populations interbreed Time Populations become allopatric Populations become sympatric Populations cannot interbreed Reproductive isolation: Speciation has occurred Gene pools merge: No speciation Mechanisms of Speciation