1. Evolution Chapters 16,17,19.2 1

2. Voyage of the Beagle- (1831-1836) Charles Darwin (1809 - 1882)  While ship was docked, Darwin would make observations about the plant and animal life  Kept a journal of his observations.  Noted 3 distinctive patterns of Biological Diversity:  1. Species vary globally  2. Species vary locally  3. Species vary over time  The Galapagos Islands – close together, but had different environments and different animals and plants  tortoise shell and finch beak 2

3. Charles Darwin Observations Finch Beak Tortoise Shell 3

4. Voyage of the Beagle- (1831-1836) Charles Darwin (1809 - 1882)  Living Organisms and Fossils  Darwin collected fossils, once living organisms, and noted that some fossils of extinct animals were similar to some living species, while others were different. 4

5. Contributions to Theories of Evolution Evolution – a change over a long period of time. Theory – a well supported, testable explanation of phenomena Geology and Fossils  Lyell (1785) & Hutton (1833) helped shape Darwin’s research  Helped scientists recognize that earth is millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present  Uniformitarianism:  Processes that change Earth in past are same as today 5

6. Contributions to Theories of Evolution Living Organisms Change  Lamarck (1809)  Proposed that organisms could change during their lifetime by selectively using or not using various parts of their bodies.  Also suggested that individuals could pass these acquired traits on to their offspring, enabling species to change over time.  Stated organisms have an inborn drive to become perfect.  Lamarck incorrect:  Organisms do not have a tendency towards perfection  Acquired traits can not be passed on to offspring 6

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8. Contributions to Theories of Evolution Population Growth  Malthus (1798)  If the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.  More births than deaths.  Applied to plants and animals more than to humans  Human populations limited by:  Limited resources  Adverse conditions  Artificial Selection 8

9. Charles Darwin “On The Origin of Species”  Prompted to publish by Alfred Russel Wallace  Published a short essay in 1958  Darwin published in 1859  Proposed the mechanism for evolution  Evolution has been taking place for millions of years- and continues in all living things 9

10. Inherited Variation and Artificial Selection  In artificial selection, nature provides the variation, and humans select those variations that they found useful  Selectively breeding only the largest hogs, fastest horses, or cows that produce most milk. 10

11. Evolution by Natural Selection 1. The struggle for existence  Members of each species compete regularly to obtain food, living space and other necessities of life. 2. Variation and Adaptation  Result of adaptations- inherited characteristic that increases an organism’s chance of survival 3. Survival of the fittest – how well you can survive and reproduce. 4. Natural selection  Over time, natural selection results in changes in inherited characteristics of a population 5. Descent with modification  Todays organisms look different than their ancestors because the changes are inherited. 11

12. Adaptations 12

13. Natural Selection 13

14. Evidence of Evolution 1. Fossil Record  Remains of ancient life  Different layers of rock formed at different times  Trilobite 2. Biogeography = Geographic Distribution of living species  Existence of similar but unrelated living organisms.  Island Finches- descendants with modifications from common mainland ancestor. 14

15. Evidence of Evolution 3. Homologous body structures  Structures that are shared by related species and that have been inherited from a common ancestor.  Structures that develop from same embryonic tissue.  Same structure but different function! 15

16. 4. Analogous structures – Body parts that share a common function, but not structure. 16 Evidence of Evolution

17. 5. Vestigial Structures – inherited from ancestors but have lost much or all of their original function due to different selection pressures acting on the descendant. 17 Evidence of Evolution

18. 6. Embryology – Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor. 18

19. Summary of Darwin  There is variation in organisms (which is heritable).  Organisms produce more offspring than can survive.  There is competition for limited resources.  Natural selection is always taking place.(Those that are most “fit” survive to reproduce, and those that are not, die.  Species living today are descended, with modification, from ancestor species. 19

20. Chapter 17 Evolution of Populations 20

21. Evolution of Populations  Combined the work of Mendel and Charles Darwin in the 1930’s  Populations, not individual organisms, evolve.  Fitness is an organism’s success in passing genes to next generation. 21

22. Evolution is a change in the relative frequency in a gene pool.  Gene pool : all genes including the different alleles that are present in a population  Allele frequency : Number of times that the allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene. 22

23. Sources of genetic Variation 1. Mutations  Any change in the sequence of DNA of a cell.  Could be a gene change or a chromosomal change.  Most mutations are neutral. 2. Genetic Recombination in Sexual Reproduction  Individuals are not exact copies of parents.  Crossing over and independent assortment during meiosis occurs creating more variety among gametes. 23

24. Single and Polygenic Genes  Single gene trait- Controlled by one gene that has two alleles  Polygenic trait- controlled by two or more genes  Height  Skin color  Eye color 24

25. Natural Selection on Single Gene Traits  Lead to changes in allele frequency and thus changes in phenotypic frequencies hence evolution.  A brown lizard experiences a mutation that produces red and black forms  What would happen?  Why did the back lizard grow in population size? 25

26. Natural Selection on Polygenic traits.  More complex then single-gene traits  Phenotypes can be affected in three ways:  1. Directional selection  Individuals at one end of the curve have higher fitness  Some individuals fail to survive/reproduce  Bell curve will shift in either direction depending on the favorite. 26

27. Natural Selection on Polygenic traits.  2. Stabilizing selection  Individuals near the center of the curve have higher fitness  Bell curve doesn’t move, but narrows  Birth Weight 27

28.  3. Disruptive selection  When individuals at both ends of the curve are fitter than individuals in the middle.  Bell curve dips in the center, acts against the intermediate type.  Bird Seed 28 Natural Selection on Polygenic traits.

29. 29 Natural Selection on Polygenic traits.

30. Genetic Drift  Natural selection is not the only source of evolution  Genetic Drift- changes in the allele frequency due to a random event or by chance.  Only in small populations  2 types 1. Bottleneck effect – a natural disaster or disease can dramatically reduce the size of a population 2. Founder effect – the allele frequencies change as a result of the migration of a small subgroup of a population. - Colonizing a new habitat 30

31. Hardy-Weinberg equilibrium  Genetic Equilibrium - allele frequencies in its gene pool do not change.  If allele frequency remains same: population won’t evolve  Hardy-Weinberg predicts 5 Conditions that can disturb genetic equilibrium and cause evolution to occur:  1. Small population size - genetic drift occurs, a small population will be impacted over a large population.  2. Non-Random mating - selection of mates regardless of their traits.  3. Mutations – introduce new alleles into the gene pool.  4. Immigration or emigration – introduce new alleles or remove alleles from a population.  5. Natural selection – different genotypes and phenotypes have a different fitness. 31 5 fingers of evolution video

32. Formation of Species: Speciation  Species – can interbreed and produce fertile offspring.  When the members of two populations cannot interbreed and produce fertile offspring  Example: Mule  Horse + Donkey  Speciation – the formation of a new species  Reproductive Isolation – A population has split into two groups, and the changes in one of those gene pools cannot spread to the other and the two groups can no longer breed. 3 Mechanisms for Reproductive Isolation to occur: 1. Behavioral Isolation - Can interbreed, but have developed different mating rituals 2. Geographic isolation - Separated by geographic barriers such as rivers, mountains, lakes, etc. 3. Temporal Isolation - Reproduce at different times 32

33. Speciation in Darwin’s Finches 1. Founders Effect  Birds arrive to islands from mainland 2. Geographic Isolation  On different islands 3. Changes in gene pool  Overtime, each finch became adapted to local environment 4. Behavioral reproductive isolation  Don’t have desirable traits or courtship rituals to other finches. 5. Competition & Continued Evolution  Natural selection 33

34. Ch 19.2 Patterns of Evolution 1. Extinction  99% of all species are extinct. Why? 2. Gradualism  A slow, steady change in a particular line of descent. 3. Punctuated Equilibrium  Involves stable periods interrupted by rapid changes. 34

35. Patterns of Evolution 3. Adaptive Radiation  The process by which a single species or a small group of species evolve over a short time into several different forms that live in different ways. 4. Convergent Evolution  Evolution produces similar structures and characteristics in distantly related organisms.  Unrelated organisms resemble each other  Examples: Penguin (Bird), Dolphin (Mammal), Shark (Fish). 35

36. Patterns of evolution 5. Coevolution  Two specifies evolve together in response to changes in each other over time.  The evolution of organisms that are ecologically connected to each other and can’t survive without each other.  As one evolves, the other will evolve with it  Acacia tree and fire ants  Bees Pollinate the flowers 36