Processes of Evolution

1. 15 Processes of Evolution

2. Chapter 15 Processes of Evolution • Key Concepts • 15.1 Evolution Is Both Factual and the Basis of Broader Theory • 15.2 Mutation, Selection, Gene Flow, Genetic Drift, and Nonrandom Mating Result in Evolution • 15.3 Evolution Can Be Measured by Changes in Allele Frequencies • 15.4 Selection Can Be Stabilizing, Directional, or Disruptive

3. Chapter 15 Mechanisms of Evolution • Key Concepts • 15.5 Genomes Reveal Both Neutral and Selective Processes of Evolution • 15.6 Recombination, Lateral Gene Transfer, and Gene Duplication Can Result in New Features • 15.7 Evolutionary Theory Has Practical Applications

4. Chapter 15 Opening Question How do biologists use evolutionary theory to develop better flu vaccines?

5. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • Evolution is the change in genetic composition of populations over time. • Evolutionary change is observed in laboratory experiments, in natural populations, and in the fossil record. • These underlying genetic changes drive the origin and extinction of species and fuel the diversification of life.

6. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • Evolutionary theory is the understanding and application of the processes of evolutionary change to biological problems. • Applications: • Study and treatment of diseases • Development of crops and industrial processes • Understanding the diversification of life • It also allows us to make predictions about the biological world.

7. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • Theory—in everyday speech, an untested hypothesis or a guess • Evolutionary theory is not a single hypothesis • It refers to our understanding of the processes that result in genetic changes in populations over time and to our use of that understanding to interpret changes we observe in natural populations.

8. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • Even before Darwin, biologists had suggested that species had changed over time, but no one had proposed a convincing mechanism for evolution.

9. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory Charles Darwin was interested in geology and natural history.

10. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory In 1831, Darwin began a 5-year voyage around the world on a Navy survey vessel, the HMS Beagle.

11. Figure 15.1 The Voyage of the Beagle

12. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • From the observations and insights made on the voyage and new ideas from geologists on the age of the Earth, Darwin developed an explanatory theory for evolutionary change: • Species change over time • Divergent species share a common ancestor (descent with modification) • The mechanism that produces change is natural selection www.PoL2e.com/at15.1 (15.4) www.PoL2e.com/ap/link15.6 (10 min.) - Bozeman www.Pol2e.com/ap/link15.7 (8min)

13. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • In 1858, Darwin received a paper from Alfred Russel Wallace with an explanation of natural selection nearly identical to Darwin’s. • Both men are credited for the idea of natural selection. • Darwin’s book, The Origin of Species, was published in 1859.

14. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • By 1900, the fact of evolution was established, but the genetic basis of evolution was not yet understood. • Then the work of Gregor Mendel was rediscovered, and during the 20th century, work continued on the genetic basis of evolution. • A “modern synthesis” of genetics and evolution took place 1936–1947. • www.PoL2e.com/at15.1 (#9, - 15.4_

15. Figure 15.2 Milestones in the Development of Evolutionary Theory

16. Concept 15.1 Evolution Is Both Factual and the Basis of Broader Theory • The structure of DNA was established by 1953 by Watson and Crick. • In the 1970s, technology developed for sequencing long stretches of DNA and amino acid sequences in proteins. • Evolutionary biologists now study gene structure and evolutionary change using molecular techniques.

17. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • In biology, “evolution” refers specifically to changes in the genetic makeup of populations over time. • Population—a group of individuals of a single species that live and interbreed in a particular geographic area at the same time. • Individuals do not evolve; populations do. • Name 3 sources for genetic variation (THINK Meiosis)?

18. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • The origin of genetic variation is mutation. • Mutation—any change in nucleotide sequences. • Mutations occur randomly with respect to an organism’s needs; natural selection acts on this random variation and results in adaptation.

19. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Mutations can be deleterious, beneficial, or have no effect (neutral). • Mutation both creates and helps maintain genetic variation in populations. • Mutation rates vary, but even low rates create considerable variation.

20. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Because of mutation, different forms of a gene, or alleles, may exist at a locus. • Gene pool—sum of all copies of all alleles at all loci in a population • Allele frequency—proportion of each allele in the gene pool • Genotype frequency—proportion of each genotype among individuals in the population

21. Figure 15.3 A Gene Pool

22. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • An experiment demonstrates how mutations accumulate in populations: • Lines of E. coli were grown in the laboratory for 20,000 generations, and genomes were sequenced every 5,000 generations. • The lines accumulated about 45 changes to their genomes, and these changes appeared at a fairly constant rate.

23. Figure 15.4 Mutations Accumulate Continuously

24. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • The gene pools of nearly all populations contain variation for many traits. • Selection that favors different traits can lead to many different lineages that descend from the same ancestor. • Artificial selection on different traits in a single species of wild mustard produced many crop plants.

25. Figure 15.5 Many Vegetables from One Species Artificial selection on different traits in a single European species of a wild mustard produced these varieties: Cabbage, cauliflower, Brussel sprouts, broccoli, kohlrabi and Kale

26. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Many of Darwin’s observations of variation and selection came from domesticated plants and animals. • Darwin bred pigeons and recognized similarities between selection by breeders and selection in nature. • In both cases, selection simply increases the frequency of the favored trait from one generation to the next.

27. Figure 15.6 Artificial Selection

28. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Laboratory experiments also demonstrate genetic variation in populations. • Selection for certain traits in the fruit fly Drosophila melanogaster resulted in new combinations of genes that were not present in the original population.

29. Figure 15.7 Artificial Selection Reveals Genetic Variation 35 generations

30. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Natural selection increases the frequency of beneficial mutations in the population. • Far more individuals are born than survive to reproduce. • Offspring tend to resemble their parents but are not identical to their parents or to one another. • Differences among individuals affect their chances of survival and reproduction, which will increase the frequency of favorable traits in the next generation.

31. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Adaptation—a favored trait that evolves through natural selection • Adaptation also describes the process that produces the trait. • Individuals with deleterious mutations are less likely to survive, reproduce, and pass their alleles on to the next generation.

32. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Migration of individuals or movement of gametes (e.g., pollen) between populations results in gene flow, which can change allele frequencies.

33. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Genetic drift—random changes in allele frequencies from one generation to the next • In small populations, it can change allele frequencies. • Harmful alleles may increase in frequency, or rare advantageous alleles may be lost. • Even in large populations, genetic drift can influence frequencies of neutral alleles. • www.PoL2e.com/at15.2

34. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Population bottleneck—an environmental event results in survival of only a few individuals • This can result in genetic drift and changing allele frequencies. • Populations that go through bottlenecks loose much of their genetic variation. This is a problem for small populations of endangered species.

35. Figure 15.8 A Population Bottleneck

36. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Founder effect—genetic drift changes allele frequencies when a few individuals colonize a new area • It is equivalent to a large population reduced by a bottleneck.

37. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Nonrandom mating: • Self-fertilization is common in plants. When individuals prefer others of the same genotype, homozygous genotypes will increase in frequency, and heterozygous genotypes will decrease.

38. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Sexual selection occurs when individuals of one sex mate preferentially with particular individuals of the opposite sex rather than at random. • Some seemingly nonadaptive traits may make an individual more attractive to the opposite sex. • There may be a trade-off between attracting mates (more likely to reproduce) and attracting predators (less likely to survive).

39. Figure 15.9 What Is the Advantage?

40. Figure 15.10 Sexual Selection in Action (Part 1)

41. Figure 15.10 Sexual Selection in Action (Part 2)

42. Concept 15.2 Mutation, Selection, Gene Flow,Genetic Drift, and Nonrandom Mating Result in Evolution • Studies of African long-tailed widowbirds showed that females preferred males with longer tails. • Males with artificially elongated tails attracted four times more females than males with artificially shortened tails. • Thus males with long tails pass on their genes to more offspring, which leads to the evolution of this unusual trait.

43. Concept 15.3 Evolution Can Be Measured by Changes in Allele Frequencies • Evolution can be measured by changes in allele frequencies. • Allele frequency:

44. Concept 15.3 Evolution Can Be Measured by Changes in Allele Frequencies • For two alleles at a locus, A and a, three genotypes are possible: AA, Aa, and aa. • p = frequency of A;q = frequency of a

45. Concept 15.3 Evolution Can Be Measured by Changes in Allele Frequencies • For each population, • p + q = 1, and q = 1 – p.

46. Concept 15.3 Evolution Can Be Measured by Changes in Allele Frequencies www.PoL2e.com/at15.3 • Hardy–Weinberg equilibrium—a model in which allele frequencies do not change across generations; genotype frequencies can be predicted from allele frequencies • For a population to be at Hardy–Weinberg equilibrium, there must be: • random mating • infinite population size • no mutation • no gene flow (no immigration or emigration) • no selection of genotypes.

47. Concept 15.3 Evolution Can Be Measured by Changes in Allele Frequencies • At Hardy–Weinberg equilibrium, allele frequencies do not change. • Genotype frequencies after one generation of random mating: • Genotype: AA Aa aa • Frequency: p2 2pq q2

49. Figure 15.12 One Generation of Random Mating Restores Hardy–Weinberg Equilibrium (Part 1)

50. Figure 15.12 One Generation of Random Mating Restores Hardy–Weinberg Equilibrium (Part 2)