1. CHAPTER 17 Evolution of Populations

2. 17.1 Genes and Variation Genetics Joins Evolutionary Theory
Heritable traits are controlled by genes
Variation is the raw material for natural selection

3. Genotype and Phenotype in Evolution
Alleles: specific forms of a gene
Genotype is the particular combination of alleles
Natural selection acts directly on phenotype, not genotype

4. Populations and Gene Pools
Members of a population interbreed, creating gene pools
Gene pool consists of all genes
Allele frequency: number of times an allele occurs in a gene pool

5. Sources of Genetic Variation
Genetics enable us to understand how heritable variation is published
3 sources of genetic variation: mutation, genetic recombination, lateral gene transfer

6. Mutations Mutation: change in genetic material of a cell
Some mutations may be lethal
Mutations move from generation to generation

7. Genetic Recombination in Sexual Reproduction
Crossing-over is another way genes are recombined
Crossing-over increases the number of genotypes
Mutations aren’t only source of heritable variation

8. Lateral Gene Transfer
Lateral gene transfer: passing genes from organism to organism that isn’t offspring
Can increase genetic variation
Important to evolution of antibiotic resistance in bacteria

9. Single-Gene and Polygenic Traits
Genes control phenotypes in different ways
Number of phenotypes on how many genes control the trait

10. Single-Gene Traits Trait controlled by only one gene
May have just two or three distinct phenotypes
Controlled by dominant and recessive alleles

11. Polygenic Traits Controlled by two or more genes
Often has two or more alleles
Creates a bell-shaped curve

12. 17.2 Evolution as Genetic Change in populations How Natural Selection Works
Passes copies of its genes to its offspring
Genetically controlled traits

13. Natural Selection on Single-Gene Traits
Can lead to changes in allele frequencies
Lead to changes in phenotype frequencies
Mutation will help them survive and adapt

14. Natural Selection on Polygenic Traits
Affect relative fitness of phenotypes
Produce three types of selection
Directional selection, stabilizing selection, disruptive selection

15. Genetic Drift Random change in allele frequency
Natural selection isn’t only source of evolutionary change

16. Genetic Bottlenecks
Change in allele frequency following dramatic reduction in population size
Sharply reduce population’s genetic diversity
Different alleles than original population

17. The Founder Effect Occur when few individuals colonize a new habitat
New gene pool is different than the parent gene pool
Change in allele frequency by migration of small subgroup

18. Evolution Versus Genetic Equilibrium
Allele frequencies don’t change
Population is not evolving

19. Sexual Reproduction and Allele Frequency
Gene shuffling during sexual reproduction produces gene combinations
Meiosis and fertilization don’t change allele frequencies
Populations would remain at genetic equilibrium

20. The Hardy-Weinberg Principle
Allele frequencies should remain constant unless factors cause it to change
Makes predictions like Punnet squares
Predict frequencies of genotypes

21. 17.3 The process of speciation Isolating Mechanisms
Speciation: formation of a new species
Gene pool can split

22. Behavioral Isolation Differences in courtship rituals
Other behavioral differences can occur
Use different song to attract mates (east meadowlark v. west meadowlark)

23. Geographic Isolation Geographic barriers Separate gene pools form
Barriers don’t always guarantee isolation

24. Temporal Isolation Reproduce at different times
Orchids in the same rain forest are examples
Can’t pollinate with each other

25. Speciation in Darwin’s Finches
Occurred by founding of a new population
Galapagos Islands

26. Founders Arrive Caused by founder effect
Allele frequencies differed from parent allele frequencies
New species formed

27. Geographic Isolation
Combination of founder effect, geographic isolation, and natural selection
Group of finches moved to another island
Another gene pool formed on that island

28. Changes in Gene Pools Adapted to its local environments
New phenotypes occur as well
Not only birds, but plants too

29. Behavioral Isolation
Different evolution causes them not to be attracted to each other
Could lead to reproductive isolation
Gene pools remain isolated

30. Competition and Continued Evolution
Compete for food
More specialized birds have less competition
Evolution of species increases over time

31. 17.4 Molecular Evolution Timing Lineage Splits: Molecular Clocks
Molecular clock uses mutation rates in DNA
Compare stretches of DNA to mark evolutionary time

32. Neutral Mutations as “Ticks”
Molecular clock relies on a repeating process
Causes slight changes in sequence of DNA
Under powerful pressure of natural selection

33. Calibrating the Clock Many different clocks
Different “ticks” at different rates
Some genes accumulate faster than others

34. Gene Duplication Genes evolve through duplication
Modern genes descended from smaller number of genes

35. Copying Genes Carry several options of various genes
Can carry two copies of the same gene
An entire genome can be duplicated

36. Duplicate Genes Evolve
Undergo mutations to change their function
Evolve without effecting original gene function
Undergo copies

37. Gene Families Produce hemoglobins Focus on Hox genes
Group of related gene called gene family

38. Developmental Genes and Body Plans
“evo-devo”
Produce evolutionary changes we see in the fossil record

39. Hox Genes and Evolution
Determine which parts of an embryo develop
Control size and shape
Can produce large changes in adults

40. Timing is Everything Starts to grow at certain time
Grows for a specific time
Stops growing at a specific time