Lecture 9 E volution:

1. Lecture 9 Evolution: Now Playing: Snog “The Human Germ”

2. Goals: 1. Define truth, geological record, phylogeny, cladistics 2. Review naïve inductivism, understand concepts of truth, materialism, naturalism, replication, saltation, punctuated equilibrium, missing links, thermodynamics, speciation,predictability, natural selection, chance 3. Relate topics to life, science, health and agriculture Assignment: Read: Chapter 16, 17, 18 Websites: http://www.religioustolerance.org/abs_true.htmhttp://earth.ics.uci.edu/ http://www.cs.colorado.edu/~lindsay/creation/index.html http://lrc.geo.umn.edu/people/teed/papers/macroev.html http://www.intellectualcapital.com/issues/issue178/item1315.asp http://www.religioustolerance.org/evolutio.htm http://www.mun.ca/biology/scarr/3900_Fossils.htm http://www.fossilnews.com/1996/cladistics.html

3. Microevolution Vs Macroevolution: Definitions Variation Selection Survival Reproduction

4. Variation Mutations- new alleles Natural Selection Genetic Drift Gene Flow Selection Directional Selection Stabilizing Selection Disruptive Selection Survival Selective forces Abiotic- weather, nature Biotic- diseases Competition Reproduction Advantageous traits must be passed to progeny Ability to pass on the genotype to the next generation is the measure of success Mechanism of Evolution

5. Microevolution Changes with in species Well defined mechanism Easily observed Based on selection Macroevolution Change from one species to another Undefined mechanism Interpretation of: Cladistics Fossil record Geological data Biological Change Over Time

6. Microevolutionary Processes • Drive a population away from genetic equilibrium • Small-scale changes in allele frequencies brought about by: • Natural selection • Gene flow • Genetic drift

7. Genetics Microevolution changes a population not individuals Traits in a population vary among individuals Microevolution is change in frequency of traits Natural Selection Reproductive success for winning phenotypes Acts directly on phenotypes and indirectly on genotypes The first changed individual has no advantage Microevolution

8. The Gene Pool All of the genes in the population Genetic resource that is shared (in theory) by all members of population Phenotype Variation Two copies of each gene (2 alleles) Inherit different allele combinations Different combinations= different phenotypes Inherit genotype, NOT phenotypes Variation is inherited

9. Genotypes, Phenotypes and Environmental Effects Himalayan rabbit experiment • Pluck hare • Grow hair with cold pack Rabbits share genotype but phenotype is dependent on environmental conditions Fig. 10.18, p. 166

10. 5 Rules for Equilibrium No mutation No immigration/ emigration Gene doesn’t affect survival or reproduction Large population Random mating Interpreted No Variation No Variation No selection No selection No selection Genetic EquilibriumAllele frequencies at a locus are not changing

11. What happens when the rules are broken?

12. Rule #1 No Mutation • Biological information changes • Each gene has own mutation rate • What determines rates? • Effect of mutations on selection • Lethal • Neutral • Advantageous

13. Reorganizing Information Changing Information Variation in the gene pool? • Recombination • Crossing over at meiosis I • Independent assortment • Meiosis II (haploid germ cells) • Fertilization • Haploid + haploid = diploid • Changes in chromosome number or structure • Mutations

14. Variation Eastern bluebird Western bluebird Mountain bluebird

15. Rule #2 No Immigration • Immigration from a separate, segregated populations • New variation • Alleles • Mutations • Effects of immigration • Shifts allele frequency • Introduces new mutations through breeding

16. Gene Flow • Physical flow of alleles into a population • Tends to keep the gene pools of populations similar • Counters the differences between two populations that result from mutation, natural selection, and genetic drift

17. Rule #3 Survival or Reproductive Advantage What does selection do for a population? Survival advantage or Reproductive advantage

18. Pillars of Natural Selection • Individuals of all populations have the capacity to produce more offspring than the environment is able to support, so individuals must compete for resources. • Individuals of a population vary in size, form, and other traits. The variant forms of a trait may be more or less adaptive under prevailing conditions. • When a form of a trait is adaptive under prevailing conditions, and when it has a heritable basis, its bearers tend to survive and reproduce more frequently than individuals with less adaptive forms of the trait. Over generations, the adaptive version becomes more common in the population. • Natural selection is the result of differences in survival and reproduction among individuals of a population that differ from one another in one or more traits. • Natural selection results in modifications of traits within a line of descent. Over time, it may bring about the evolution of a new species, with an array of traits uniquely its own.

19. Basics of Natural SelectionCapacity and Competition • All populations have the capacity to increase in numbers • No population can increase indefinitely • Eventually, the individuals of a population will end up competing for resources

20. Basics of Natural SelectionCapacity and Competition • The alleles that produce the most successful phenotypes will increase in the population • Less successful alleles will become less common • Change leads to increased fitness • Increased adaptation to a specific environment

21. Results of Natural Selection Three possible outcomes: • Directional selection • Decreases variation in favor of an extreme. • Stabilizing selection • Selects most average/ common form of a trait • Disruptive selection • Selects against intermediate forms

22. Directional Selection Number of individuals in the population • Allele frequencies shift in one direction Range of values for the trait at time 1 Number of individuals in the population Range of values for the trait at time 2 Number of individuals in the population Range of values for the trait at time 3

23. Microevolution: Any change below the level of species: • change in the base pair sequence of DNA or RNA • A gene frequency within a population or a species • allelic effects on the form, or phenotype, of organisms that make up that population or species. Industrial Melanism

24. Stabilizing Selection Number of individuals in the population • Intermediate forms are favored and extremes are eliminated Range of values for the trait at time 1 Range of values for the trait at time 2 Range of values for the trait at time 3

25. Antibiotic Resistance Bacteria Antiviral Resistance HIV Pesticide Resistance Insects Chemical kills susceptible individuals Resistant individuals survive If resistance is heritable, following generations exhibit the same trait. Resistance

26. Example: Pesticide Resistance Evolution in Action The DDT Paradigm

27. Pre-adapted to survive 99% Non-resistant die Spray Pesticide 100% resistant survive

28. Spray with an Insecticide Second generation Second generation survivors

29. Spray with an Insecticide Third generation Third generation survivors

30. Mutation rate = 1 x 10-4 or 1 in 10,000 100 butterflies

31. 1 million butterflies Beneficial mutation = 1 x 10-9 or 1 in 1,000,000,000

32. Insects Evolve at a High Rate Breeding “super-bugs” in the home?

33. -Antibiotic resistance -Food safety -Bioterrorism -GMO foods

34. Disruptive Selection Number of individuals in the population • Forms at both ends of the range of variation are favored • Intermediate forms are selected against Range of values for the trait at time 1 Number of individuals in the population Range of values for the trait at time 2 Number of individuals in the population Range of values for the trait at time 3

35. Balanced Polymorphism • Polymorphism - “having many forms” • Occurs when two or more alleles are maintained at frequencies greater than 1 percent

36. Sexual Selection • Selection favors certain secondary sexual characteristics • Through nonrandom mating, alleles for preferred traits increase • Leads to increased sexual dimorphism

37. Sickle-Cell Trait: Heterozygote Advantage • Allele HbS causes sickle-cell anemia when heterozygous • Heterozygotes are more resistant to malaria than homozygotes Malaria case Sickle cell trait less than 1 in 1,600 1 in 400-1,600 1 in 180-400 1 in 100-180 1 in 64-100 more than 1 in 64

38. Rule #4 Large Population What happens if the population or allele frequency gets wacked?

39. Genetic Drift • Random change in allele frequencies • Most pronounced in small populations • Sampling error - Fewer times an event occurs, greater the variance in outcome • Fixation: one allele is established in a population

40. Founder Effect Small number of individuals start a new population Low probability that allele frequencies are the same as original population Effect is pronounced on isolated islands Bottleneck A severe reduction in population size Causes pronounced drift Results All progeny will be very similar. Gene pool very shallow

41. Rule #5 Random Mating

42. Inbreeding • Nonrandom mating between related individuals • Leads to increased homozygosity • Can lower fitness when deleterious recessive alleles are expressed

43. 5 Rules for Equilibrium No mutation No immigration/ emigration Gene doesn’t affect survival or reproduction Large population Random mating Interpreted No Variation No Variation No selection No selection No selection Genetic EquilibriumAllele frequencies at a locus are not changing

44. Macroevolution and Speciation • Biological evolution is the theory that all living things are modified descendants of a common ancestor that lived in the distant past, or “descent with modification.” • Evolution simply means change over time. Descent with modification occurs because all organisms within a single species are related through descent with modification

45. Biological Species Concept “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” Ernst Mayr

46. Morphology & Species • Morphological traits may not be useful in distinguishing species • Members of same species may appear different because of environmental conditions • Morphology can vary with age and sex • Different species can appear identical

47. Variable Morphology Grown in water Grown on land

48. Reproductive Isolation Cornerstone of the biological species concept Speciation is the attainment of reproductive isolation Reproductive isolation arises as a by-product of genetic change Genetic Divergence Gradual accumulation of differences in the gene pools of populations Natural selection, genetic drift, and mutation can contribute to divergence Gene flow counters divergence Isolation and Divergence

49. Prezygotic Isolation Ecological Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Mortality Postzygotic Isolation Zygotic mortality Hybrid inviability Hybrid sterility Reproductive IsolationCan’t allow gene flow Zygote is a fertilized egg

50. Speciation Allopatric Different lands, (physical barrier) Sympatric Same lands (no physical or ecological barrier Parapatric Same border (small hybrid zone)