1. Evolution A Scientific Explanation for Similarities and Differences Between Species

2. Evolution Evolution = progressive change in characteristics of organisms as a result of changes in genetic compositionEvolution = progressive change in characteristics of organisms as a result of changes in genetic composition Two important aspectsTwo important aspects –Descent from a common ancestor –Adaptation to the environment Adaptation = characteristic that makes it more likely that an organism will survive and reproduce in its environmentAdaptation = characteristic that makes it more likely that an organism will survive and reproduce in its environment

3. A Flowchart of Evolutionary Reasoning Potential for rapid reproduction Relatively constant resources and population over time Variability in structures and behaviors Some variability is inherited; adaptations increase in future generations (observations) (conclusions) Competition for survival and reproduction (1) NATURAL SELECTION On average, the fittest organisms leave the most offspring (2) EVOLUTION: The genetic makeup of the population changes over time, driven by natural selection (3) Formation of new genotypes leads to phenotypic variation Struggle for existence Survival of the fittest Adaptation

4. Natural Selection As the Mechanism for Evolution An increase in frequency of genotypes that confer a favorable advantage in a given environment.

5. Applying Your Knowledge A.The mechanism for evolution is B.A progressive change in the characteristics of organisms is C.A trait that makes a species survival more likely is called a(n) 1.Adaptation 2.Evolution 3.Natural selection

6. Evidence for Common Descent From the Fossil Record Progressive changes from simpler to more complex organisms can be seen in the fossil record.

7. Biogeographical Evidence for Common Descent Different island species resemble each other. Different island species resemble each other.

8. Biogeographical Evidence for Common Descent Island Populations resemble those on nearby land. The Galapagos finches resembled the grassquit found on the coast of Ecuador.

9. Anatomical Evidence for Common Descent: Homologous Structures Flying Swimming Running Grasping

10. Anatomical Evidence: Vestigial Structures Functional hindlimb in salamander Remnants of hindlimb seen in boa and whale

11. Evidence for Common Descent from Biochemistry

12. Evidence for Evolution from Biochemistry Similarities in sequence measured by ease of separating DNA strands by heat Similarities in sequence measured by ease of separating DNA strands by heat

13. Evidence for Evolution: Genetics Mutation generates diversityMutation generates diversity Meiosis and Fertilization generate new combinations due toMeiosis and Fertilization generate new combinations due to –Crossing Over –Alternate patterns of chromosome segregation –Unique genotype of fertilizing sperm combined with unique genotype of egg

14. Two Types of Evolution MicroevolutionMacroevolution Change within a population or species Change to a new species

15. Microevolution led to an increase in dark- winged Pepper Moths in industrial regions of Britain.

16. Evolution As a Change in Genotypes GenotypePhenotype SS No disease Susceptible to Malaria SS’ Sickle Cell Trait (mild symptoms) Resistant to Malaria S’S’ Sickle Cell Anemia Die from anemia Individuals carrying the S’ allele were more likely to survive when malaria is the selecting agent.

17. Malaria as an Agent of Natural Selection S’S’ S’S’ SS SS SS’ SS’ SS’SSS’S’ Malaria Eliminates SS XX X Anemia Eliminates S’S’ XX X SS’ SS’ SS’RemainingGenotypes

18. Hardy-Weinberg Equilibrium A condition where allele frequencies andA condition where allele frequencies and genotypic frequencies remain constant from generation to generation genotypic frequencies remain constant from generation to generation Changes from equilibrium values are used to determine if natural selection is occurringChanges from equilibrium values are used to determine if natural selection is occurring

19. Hardy-Weinberg Equilibrium Allelic Frequencies p + q = 1 p = frequency of dominant allele (eg. A) q = frequency of recessive allele (eg. a) Genotypic Frequencies p 2 + 2pq + q 2 = 1 p 2 = freq. of homozygous dominants (AA) q 2 = freq. of homozygous recessives (aa) 2pq = frequency of heterozygotes (Aa) Conditions Large population size Random mating No migration No mutation No selection

20. Example Using Hardy-Weinberg Equilibrium If the frequency of albinos in a population is 9%, what is the frequency of AA and Aa genotypes?If the frequency of albinos in a population is 9%, what is the frequency of AA and Aa genotypes? Let A = allele for normal skin pigmentationLet A = allele for normal skin pigmentation Let a = allele for albinismLet a = allele for albinism

21. .7A.3a.7A.3a.49AA.21Aa.09aa

22. Applying Hardy-Weinberg Equilibrium Values to RFLP Analysis

23. Conditions of Hardy-Weinberg Equilibrium Condition Non-equilibrium Condition Large Population Size Genetic Drift: Changes in allele frequency due to small population sizes 1. Founder effect 1. Founder effect 2. Population Bottleneck 2. Population Bottleneck

24. Conditions of Hardy-Weinberg Equilibrium Condition Non-equilibrium Condition Random Mating Non-random mating: Alters genotypic but not allelic frequencies

25. Conditions of Hardy-Weinberg Equilibrium Condition Non-equilibrium Condition No Migration Migration: Can add new alleles, remove alleles or change allele frequency Leads to Gene Flow between populations

26. Conditions of Hardy-Weinberg Equilibrium Condition Non-equilibrium Condition No Mutation Mutation: Alters allele frequency, causes formation of new genotypes

27. Conditions of Hardy-Weinberg Equilibrium Condition Non-equilibrium Condition No Selection Natural Selection: Increases frequency of genotypes with higher fitness

28. Molecular Evolution Two Hypotheses for the Origin of Modern Humans

29. DNA Analyses Related to Human Origins Visit http://www.dnalc.org/ and choose Genetic Origins Mitochondrial Control Region Media and Animations Solving the Mystery of the Neanderthals http://www.dnalc.org/ Other Applications of DNA Analysis can be found at http://dnai.org Choose Applications http://dnai.org

30. Types of Selection Stabilizing: eliminates extremesStabilizing: eliminates extremes

31. Types of Selection Disruptive: increases both extremesDisruptive: increases both extremes

32. Types of Selection Directional: increases one extremeDirectional: increases one extreme

33. Applying Your Knowledge 1.Stabilizing Selection 2.Disruptive Selection 3.Directional Selection Which type of selection has occurred if The background is sandy with dark rocks and snails are found with either dark or light shell colors?The background is sandy with dark rocks and snails are found with either dark or light shell colors? After spraying with malathion, more fruit flies are found to be resistant to this insecticide?After spraying with malathion, more fruit flies are found to be resistant to this insecticide?

34. Species Formation Species = Group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groupsSpecies = Group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups Speciation depends onSpeciation depends on –isolation (lack of gene flow) –genetic divergence

35. Mechanisms for Speciation Allopatric SpeciationAllopatric Speciation –Occurs as a result of geographical isolation –Most common mechanism Sympatric SpeciationSympatric Speciation –Occurs in the same location –Can be due to ecological isolation –Can be due to Polyploidy Occurs for plants that have a sudden change in numbers of chromosome setsOccurs for plants that have a sudden change in numbers of chromosome sets

36. Single species (white mice); homogeneous habitat Geographical barrier (impassable river); isolated populations Genetic drift; genetic divergence; tan vs. white mice Barrier removed (river dries up); Mice mix but don’t interbreed. Allopatric Speciation (a) (b) (c) (d)

37. Summary of Allopatric Speciation One group separates from the population.One group separates from the population. Separate evolutionary pressures cause different genetic changes in both groups.Separate evolutionary pressures cause different genetic changes in both groups. (Is this (1) microevolution or (2) macroevolution?) (Is this (1) microevolution or (2) macroevolution?) Sufficient genetic changes accumulate so that interbreeding cannot occur if groups are rejoined.Sufficient genetic changes accumulate so that interbreeding cannot occur if groups are rejoined. (Is this (1) microevolution or (2) macroevolution?) (Is this (1) microevolution or (2) macroevolution?)

38. Sympatric Speciation Single species (white mice); homogeneous habitat (a) Climate change; two habitats; isolated because don’t mix (b) Environmental pressure to adapt; genetic divergence; tan vs. white mice (c) Sufficient divergence; now different species (d)

39. Speciation by Polyploidy Chromosomes duplicate but do not separate  Tetraploid with two sets of A and B. Diploid with chromosome set A and chromosome set B. Cross between diploid and tetraploid species  Triploid with one each of chromosome sets A, B and D. Chromosomes duplicate but do not separate  Hexaploid with three sets of A, B and D. Modern Wheat

40. Applying Your Knowledge A.Which process involves a sudden, large change in chromosome number? B.Which process requires geographical separation? C.Which process can occur as a result of small differences within the same local environment? 1.Sympatric Speciation 2.Speciation by Polyploidy 3.Allopatric Speciation

41. Patterns of Evolution DivergentDivergent –different phenotypes arise as related species encounter environmental differences

42. Patterns of Evolution ConvergentConvergent –similar phenotypes arise in unrelated species as a result of environmental similarities North American Desert Plants Cactus Euphorbs African

43. Patterns of Evolution Coevolution: species adjust together to maintain relationshipCoevolution: species adjust together to maintain relationship Flowering plants and their Pollinators Predators and their Prey