Process of Evolution

1. Process of Evolution 1 Entire population is modified Population - All members of a single species Specific area at the same time Population genetics - Gene frequencies & changes Within a population Gene pool - All alleles at all gene loci All individuals Gene frequency - % of gene pool has allele of interest Microevolution - Accumulation of small changes Gene pool

2. Determine gene frequency 2 Calculate % for single allele in the population Given: R = red eyes, r = white eyes Pop. = 200 32% = RR 52% = Rr 16% = rr 64 = RR 104 = Rr 32 = rr Total # alleles = 200 x 2 = 400 # R alleles in population? RR = (2 R x 64) = 128 Rr = (1R x 104) = 104 232 # r alleles? 400 – 232 = 168 Frequency of R? 232/400 = 0.58 58% Frequency of r? 42% 168/400 = 0.42

3. Predict ratio of genotypes next generation 3 Punnett square Parental allele ratios R = 58%, r = 42% Gametes from all members of population Sperm 0.58 R 0.42 r 0.58 R 0.34 RR 0.24 Rr Eggs 0.18 rr 0.42 r 0.24 Rr Genotype frequencies for offspring: Allele frequency? % RR = 34 % 34 x 2 = 68 + 48 = 116/200 = .58 R % Rr = 48 % .42 r 18 x 2 = 36 + 48 = 84/200 = % rr = 18 %

4. Hardy-Weinberg Principle 4 Migration into or out of population Individuals pair by chance Population must remain large 1 genotype is not favored Equilibrium of allele frequencies in a gene pool Remain constant for every generation if: 5 conditions are met: No mutations No gene flow Random mating No genetic drift No selection

5. Hardy-Weinberg Equation p + q = 1 Equilibrium gene pool Calculate genotypic & allele frequencies of population p2 + 2pq + q2 = 1.0 (100%) p2 = % homozygous dominant pq = % heterozygous individuals q2 = % homozygous recessive p = frequency of dominant allele (2 alleles) q = frequency of recessive allele q p pxp p2 p pxq p2 + 2pq + q2 q2 q pxq qxq 5

6. Example: 6 E + e = 1.0 E2 + 2Ee + e2 = 1.0 e = 0.16 16% of Columbia have attached ears E = unattached e = attached p + q = 1.0 p2 + 2pq + q2 = 1.0 Known: e2 = 0.16 Frequency of recessive allele = 0.4 Frequency of dominant allele E = 1.0 – 0.4 = 0.6 % homozygous dominant? E2 = (0.6)2 = 0.36 % are heterozygous? 2Ee = 2(0.6)(0.4) = 0.48

7. Sample problem t = 0.09 Population of pea plants, 9% are short T = tall, t = short p + q = 1 T + t = 1 T2 + 2Tt + t2 = 1 p2 + 2pq = q2 = 1 Frequency of the recessive allele (t)? 30% t2 = 0.09 = 0.3 Frequency of the dominant allele (T)? 70% T = 1.0 – 0.3 = 0.7 What are the genotypic frequencies? tt = 9% T2 = (0.7)2 = 0.49 TT = 49% 2Tt = 2(0.7)(0.3) = 0.42 Tt = 42% 7

8. Microevolution 8 Deviation from Hardy-Weinberg equilibrium Evolution occurred Small changes = evolution Mutation Gene flow Nonrandom mating Genetic drift Natural selection Hardy-Weinberg principle: Change in allele frequencies

9. Microevolution:Industrial melanism 9 Before industrial revolution After Dark > light Light > dark peppered moth Pollutants Dark seen by predators White seen by predators

10. Mutations 10 Environmental conditions Better adaptation Until all best alleles group Permanent change in genetic code Population effects: Genes >2 alleles in gene pool >2 phenotypes No immediate affect phenotype Dormant in population Right allele combinations Most favorable Recombination

11. Gene Flow 11 Gene migration Movement of alleles between populations Migration of breeding individuals Initial gene flow Mutations Novel alleles Both populations Continued gene flow Both populations - similar gene pools Decrease the genetic diversity among populations Prevent speciation

12. Nonrandom mating - Inbreeding Closely related All loci % of heterozygotes % of homozygotes Recessive abnormalities http://www.greendiary.com/entry/rare-white-bengal-tiger-is-not-a-pure-breed-but-crossbred-website-claims Constant allele frequency 12

13. Assortative Mating Same phenotype 13 http://www.snv.jussieu.fr/bmedia/ATP/dros-elv.htm Proportion of homozygotes @ specific loci http://bugguide.net/node/view/9791 Populations subdivides into 2 phenotypic classes

14. Sexual selection 14 http://www.zo.utexas.edu/faculty/sjasper/images/23.16x2.jpg http://sdakotabirds.com/species/ring_necked_pheasant_info.htm http://www.teorekol.lu.se/ekol_inst/mol_ekol/faswww/spurs.jpg Males compete Female selects phenotype

15. Genetic Drift 15 Changes in allele frequencies of a gene pool = Chance! Large pop: = little effect Small pop: Some individuals fail to breed Change in allele frequencies Rare genotype may disappear Other alleles become fixed

16. Bottleneck Effect Near extinction Natural disaster Next generation X http://www.hiren.info/desktop-wallpapers/animals-birds-pictures/posture-cheetah Over hunting Habitat loss Majority genotypes Intense in breeding Extreme genetic similarity Relative infertility 16

17. Founder effect Original colony Lancaster County Rare alleles Higher frequency Isolated from general population Carrier Dwarfism Polydactylism 17

18. Natural Selection – Biotic environment 18 Organisms seeking resources Weather conditions Population adapts - Competition - Predation - Parasitism Abiotic environment - Temperature - Precipitation

19. Evolution by Natural Selection Requirements 19 Variation: Members of populations differ Inheritance: Heritable genetic differences Differential adaptiveness: Affect how well they adapt Differential reproduction: Measure of fitness Reproduce fertile offspring Relative fitness - Fitness 1 phenotype to reproduce compared to another

20. Directional selection Favor extreme phenotype 20 Adapt changing environment Population shifts Hide among trees Low-crowned - browse Grasslands - exposed Strength Intelligence Speed Grinding teeth

21. Stabilizing selection Intermediate phenotype favored Environmental aspects remain constant Extreme selected against Swiss starlings = 4/5 eggs <4/5 = predators >4/5 = nutrients 21

22. Disruptive selection 2 or more extreme phenotypes Forested – dark shelled land snails Thrush fed on light-banded Grass fields – light-banded lands snails Thrush fed on dark 22

23. Speciation 1 species splits into 2 23 Shared gene pool Transformation of 1 species to a new Species Group of populations Members interbreed Reproductively isolated Phylogenetic species concept: DNA/DNA comparison 2 species to separate Must be reproductively isolated No gene flow Reproductive isolating mechanism: Structural Functional Behavioral

24. Pre-zygotic Isolation Before gamete fusion No attempt to reproduce Habitat isolation: Unlikely to meet Temporal isolation: Different mating season Behavioral isolation: Cannot recognize courtship Mechanical isolation: Genitalia are incompatible Gamete isolation: 2 gametes meet don’t fuse Egg has no sperm receptor 24

25. Post-zygotic Isolation After gamete fusion Hybrid offspring Zygote mortality Zygote not viable Different chromosome sets Hybrid sterility Offspring are sterile Tetrads don’t form F2 unfit Offspring are weak 25

26. Modes of Speciation Allopatric speciation 26 Build up Subspecies Prezygotic Geographically isolated No gene flow Directional selection Genetic drift Mutations Postzygotic

27. Sympatric speciation 27 Hyrid 2n = 21 x 2 = 42 Chromosome doubling 2 species w/o geographic isolation Fertile Sterile 14 n + 7 n Polyploidy

28. Adaptive Radiation 21 Several new habitats Genotypic differences Slightly hooked Allopatric speciation 1 ancestral species Subject to founder effect Parrot-like Natural selection Long, down-curved Strong, stubby beaks Goldfinch 28