Week 5!! Get ready for entrance quiz

1. Week 5!!Get ready for entrance quiz Labs—Discussions and graphs need work

2. Evolution evidence: Biogeography Geographical distribution of species Examples: Islands vs. Mainland Australia Continents

3. Evolution evidence: The Fossil Record Succession of forms over time Transitional links Vertebrate descent

4. Fossil Record

5. 2006 Fossil Discovery of Early Tetrapod Tiktaalik “missing link” from sea to land animals

6. Evolution evidence: Comparative Anatomy Homologous structures (homology) Descent from a common ancestor

7. Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor

8. Homologous structures spines leaves succulent leaves tendrils needles colored leaves

9. Analogous structures • Separate evolution of structures • similar functions • similar external form • different internal structure & development • different origin • no evolutionary relationship Don’t be fooledby their looks! Solving a similar problem with a similar solution

10. Vestigial organs Modern animals may have structures that serve little or no function remnants of structures that were functional in ancestral species deleterious mutations accumulate in genes for non-critical structures without reducing fitness snakes & whales — remains of pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone

11. Dispatch • Compare analogous to homologous structures • What are 3 pieces of evidence that whales evolved from land mammals? • Give 2 examples of vestigial structures.

12. Evolution evidence: Comparative Embryology Pharyngeal pouches, ‘tails’ as embryos

13. Evolution evidence: Molecular Biology Similarities in DNA, proteins, genes, and gene products Common genetic code • Closely related species have sequences that are more similar than distantly related species • DNA & proteins are a molecular record of evolutionary relationships

14. Building “family” trees Closely related species (branches) share same line of descent until their divergence from a common ancestor

15. Artificial selection Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties” “descendants” of wild mustard “descendants” of the wolf

16. Natural selection in action Insecticide & drug resistance insecticide didn’t kill all individuals resistant survivors reproduce resistance is inherited insecticide becomes less & less effective

17. Final words…... “Absence of evidence is not evidence of absence.”

18. Evolution on a micro level • Looking at alleles • Looking at the DNA • DARWIN DIDN”T KNOW DNA

19. Get a bottle and colored sticks

20. Microevolution, II: type of genetic drift The Bottleneck Effect: type of genetic drift resulting from a reduction in population (natural disaster) such that the surviving population is no longer genetically representative of the original population

21. Microevolution, I A change in the gene pool of a population over a succession of generations 1- Genetic drift: changes in the gene pool of a small population due to chance (usually reduces genetic variability)

22. Chapter 23~ Chapter 23~ The Evolution of Populations

23. Population genetics Population: a localized group of individuals belonging to the same species Species: a group of populations whose individuals have the potential to interbreed and produce fertile offspring Gene pool: the total aggregate of genes in a population at any one time Population genetics: the study of genetic changes in populations Modern synthesis/neo-Darwinism “Individuals are selected, but populations evolve.”

24. Conservation issues Bottlenecking is an important concept in conservation biologyof endangered species loss of alleles from gene pool reduces variation reduces adaptability Peregrine Falcon Breeding programs must consciously outcross Golden Lion Tamarin

25. Microevolution, III type of genetic drift Founder Effect:a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population just by chance some rare alleles may be at high frequency; others may be missing skew the gene poolof new population human populations that started from small group of colonists example:colonization of New World

26. Dispatch 1) Compare and contrast: -founder effect -genetic drift -bottle neck effect 2) Give 3 deadlines for October

27. Microevolution, IV 2- Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations) seed & pollen distribution by wind & insect migration of animals

28. Microevolution, V 3- Mutations: a change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for naturalselection) Mutation creates variation

29. Microevolution, VI 4- Nonrandom mating: Sexual selection inbreeding and assortive mating (both shift frequencies of different genotypes)

30. Sexual selection It’s FEMALE CHOICE, baby!

32. Microevolution, VII 5.NaturalSelection differential success in reproduction; climate change food source availability predators, parasites, diseases toxins only form of microevolution that adapts a population to its environment combinations of allelesthat provide “fitness” increasein the population

33. Natural Selection Selection acts on any trait that affects survival or reproduction predation selection physiological selection sexual selection

34. Variation & natural selection Variation is the raw material for natural selection there have to be differences within population some individuals must be more fit than others

35. Mutation random changes to DNA errors inmitosis& meiosis environmental damage Sex mixing of alleles recombinationof alleles new arrangements in every offspring new combinations = new phenotypes spreads variation offspring inherit traits from parent Where does Variation come from? Wet year Beak depth Dry year Dry year Dry year 1977 1980 1982 1984 11 10 Beak depth of offspring (mm) 9 Medium ground finch 8 8 9 10 11 Mean beak depth of parents (mm)

37. Population variation Polymorphism:coexistence of 2 or more distinct forms of individuals (morphs) within the same population Geographical variation:differences in genetic structure between populations (cline)

38. Variation preservation Prevention of natural selection’s reduction of variation Diploidy 2nd set of chromosomes hides variation in the heterozygote Balanced polymorphism1- heterozygote advantage (hybrid vigor; i.e., malaria/sickle-cell anemia); 2- frequency dependent selection (survival & reproduction of any 1 morph declines if it becomes too common; i.e., parasite/host)

39. Natural selection Fitness: contribution an individual makes to the gene pool of the next generation 3 types: A. Directional B. Diversifying C. Stabilizing

41. Effects of Selection Changes in the average trait of a population DIRECTIONALSELECTION STABILIZINGSELECTION DISRUPTIVESELECTION giraffe neck horse size human birth weight rock pocket mice

42. Sexual selection Sexual dimorphism: secondary sex characteristic distinction Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

43. Any Questions??

44. Hardy-Weinberg Theorem Serves as a model for the genetic structure of a nonevolving population (equilibrium) Evolution = change in allele frequenciesin a population hypothetical: what conditions notwould cause allele frequencies to change? non-evolving population REMOVE all agents of evolutionary change very large population size (no genetic drift) no migration (no gene flowin or out) no mutation(no genetic change) random mating(no sexual selection) no natural selection(everyone is equally fit)

45. Hardy-Weinberg Equation p=frequency of one allele (A); q=frequency of the other allele (a); p+q=1.0(p=1-q & q=1-p) p2=frequency of AA genotype; 2pq=frequency of Aa genotype; q2=frequency of aa genotype; frequencies of all individuals must add to 1 (100%), so: p2 + 2pq + q2 = 1 G.H. Hardy mathematician W. Weinberg physician

46. Using Hardy-Weinberg equation population: 100 cats 84 black, 16 white How many of each genotype? q2 (bb): 16/100 = .16 q (b): √.16 = 0.4 p (B): 1 - 0.4 = 0.6 p2=.36 2pq=.48 q2=.16 BB Bb bb What are the genotype frequencies? Must assume population is in H-W equilibrium!

47. Hardy Problem • Calculate q2 Count the individuals that are homozygous recessive in the illustration above. Calculate the percent of the total population they represent. This is q2. Calculate q Q2=4/16=0.25 Q=0.5 p + q = l. You know q, so what is p, the frequency of the dominant allele? P=0.5 Find 2pq 2pq = 2(0.5) (0.5) = 0.5 , so 50% of the population is heterozygous.

48. Problem 1 • In a certain population of 1000 fruit flies, 640 have red eyes while the remainder have sepia eyes. The sepia eye trait is recessive to red eyes. How many individuals would you expect to be homozygous for red eye color? Hint: The first step is always to calculate q2! Start by determining the number of fruit flies that are homozygous recessive. If you need help doing the calculation, look back at the Hardy-Weinberg equation.

49. Problem 2 • The Hardy-Weinberg equation is useful for predicting the percent of a human population that may be heterozygous carriers of recessive alleles for certain genetic diseases. Phenylketonuria (PKU) is a human metabolic disorder that results in mental retardation if it is untreated in infancy. In the United States, one out of approximately 10,000 babies is born with the disorder. Approximately what percent of the population are heterozygous carriers of the recessive PKU allele?