D. Deviations from HWE 1. mutation 2. migration 3. Non-random Mating 4. Finite Population Sizes: Genetic Drift The organisms that actually reproduce in a population may not be representative of the genetics structure of the population; they may vary just due to sampling error

D. Deviations from HWE 1. mutation 2. migration 3. Non-random Mating 4. Finite Population Sizes: Genetic Drift 1 - small pops will differ more, just by chance, from the original population

2 - small pops will vary more from one another than large D. Deviations from HWE 1. mutation 2. migration 3. Non-random Mating 4. Finite Population Sizes: Genetic Drift 1 - small pops will differ more, just by chance, from the original population 2 - small pops will vary more from one another than large

- “Founder Effect” D. Deviations from HWE 1. mutation 2. migration 3. Non-random Mating 4. Finite Population Sizes: Genetic Drift - “Founder Effect” The Amish, a very small, close-knit group decended from an initial population of founders, has a high incidence of genetic abnormalities such as polydactyly

- “Founder Effect” and Huntington’s Chorea HC is a neurodegenerative disorder caused by an autosomal lethal dominant allele. The fishing villages around Lake Maracaibo in Venezuela have the highest incidence of Huntington’s Chorea in the world, approaching 50% in some communities. The gene was mapped to chromosome 4, and the HC allele was caused by a repeated sequence of over 35 “CAG’s”. Dr. Nancy Wexler found homozygotes in Maracaibo and described it as the first truly dominant human disease (most are incompletely dominant and cause death in the homozygous condition).

- “Founder Effect” and Huntington’s Chorea HC is a neurodegenerative disorder caused by an autosomal lethal dominant allele. The fishing villages around Lake Maracaibo in Venezuela have the highest incidence of Huntington’s Chorea in the world, approaching 50% in some communities. By comparing pedigrees, she traced the incidence to a single woman who lived 200 years ago. When the population was small, she had 10 children who survived and reproduced. Folks with HC now trace their ancestry to this lineage.

- “Genetic Bottleneck” If a population crashes (perhaps as the result of a plague) there will be both selection and drift. There will be selection for those resistant to the disease (and correlated selection for genes close to the genes conferring resistance), but there will also be drift at other loci simply by reducing the size of the breeding population. Cheetah have very low genetic diversity, suggesting a severe bottleneck in the past. They can even exchange skin grafts without rejection… European Bison, hunted to 12 individuals, now number over 1000. Elephant seals fell to 100’s in the 1800s, now in the 100,000’s

Modern Evolutionary Biology I. Population Genetics A. Overview B. The Genetic Structure of a Population C. The Hardy-Weinberg Equilibrium Model D. Deviations From HWE:  1. Mutation 2. Migration 3. Non-Random Mating: 4. Populations of Finite Size and Sampling Error - "Genetic Drift" 5. Natural Selection: “differential reproductive success” we measure reproductive success as ‘fitness’ 1. Fitness Components:

D. Deviations From HWE:  5. Natural Selection Fitness Components: Fitness = The mean number of reproducing offspring / genotype - probability of surviving to reproductive age - number of offspring - probability that offspring survive to reproductive age

D. Deviations From HWE:  5. Natural Selection Fitness Components: Fitness = The mean number of reproducing offspring / genotype - probability of surviving to reproductive age - number of offspring - probability that offspring survive to reproductive age 2. Constraints: i. finite energy budgets and necessary trade-offs:

GROWTH METABOLISM REPRODUCTION D. Deviations From HWE: 5. Natural Selection Fitness Components: Fitness = The mean number of reproducing offspring / genotype - probability of surviving to reproductive age - number of offspring - probability that offspring survive to reproductive age 2. Constraints: i. finite energy budgets and necessary trade-offs: GROWTH METABOLISM REPRODUCTION

Maximize probability of survival D. Deviations From HWE:  5. Natural Selection Fitness Components: 2. Constraints: finite energy budgets and necessary trade-offs: TRADE OFF #1: Survival vs. Reproduction Maximize probability of survival GROWTH METABOLISM REPRODUCTION Maximize reproduction

Lots of small, low prob of survival A few large, high prob of survival D. Deviations From HWE:  5. Natural Selection Fitness Components: 2. Constraints: finite energy budgets and necessary trade-offs: TRADE OFF #1: Survival vs. Reproduction TRADE OFF #2: Lots of small offspring vs. few large offspring METABOLISM REPRODUCTION Lots of small, low prob of survival A few large, high prob of survival METABOLISM

Photosynthetic potential D. Deviations From HWE:  5. Natural Selection Fitness Components: 2. Constraints: finite energy budgets and necessary trade-offs: Contradictory selective pressures: Leaf Size Photosynthetic potential Water Retention

Photosynthetic potential D. Deviations From HWE:  5. Natural Selection Fitness Components: 2. Constraints: finite energy budgets and necessary trade-offs: Contradictory selective pressures: Leaf Size Photosynthetic potential Water Retention Rainforest understory – dark, wet Big leaves adaptive

Photosynthetic potential D. Deviations From HWE:  5. Natural Selection Fitness Components: 2. Constraints: finite energy budgets and necessary trade-offs: Contradictory selective pressures: Leaf Size Photosynthetic potential Water Retention Desert – sunny, dry Small leaves adaptive

prob. of survival (fitness) 0.8 0.4 0.2 D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: a. Calculating relative fitness p = 0.4, q = 0.6 AA Aa aa Parental "zygotes" 0.16 0.48 0.36 = 1.00 prob. of survival (fitness) 0.8 0.4 0.2 Relative Fitness 0.8/0.8=1 0.4/0.8 = 0.5 0.2/0.8=0.25 Calculate relative fitness by dividing all fitness values by the LARGEST value.

prob. of survival (fitness) 0.8 0.4 0.2 D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: a. Calculating relative fitness b. Modeling Selection p = 0.4, q = 0.6 AA Aa aa Parental "zygotes" 0.16 0.48 0.36 = 1.00 prob. of survival (fitness) 0.8 0.4 0.2 Relative Fitness 1 0.5 0.25 Survival to Reproduction 0.24 0.09 = 0.49 Multiply the initial genotypic frequency by relative fitness. Of course, not all organisms have survived, so these new frequencies do not sum to 1 any more.

prob. of survival (fitness) 0.8 0.4 0.2 D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: a. Calculating relative fitness b. Modeling Selection p = 0.4, q = 0.6 AA Aa aa Parental "zygotes" 0.16 0.48 0.36 = 1.00 prob. of survival (fitness) 0.8 0.4 0.2 Relative Fitness 1 0.5 0.25 Survival to Reproduction 0.24 0.09 = 0.49 Freq’s in Breeding Adults 0.16/0.49 = 0.33 0.24/0.49 = 0.49 0.09/0.49 = 0.18 But we need to know what FRACTION of these SURVIVORS has each genotype. So, divide each frequency by the total. THESE are the genotypic frequencies in the survivors that have reached reproductive age and will breed.

prob. of survival (fitness) 0.8 0.4 0.2 D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: a. Calculating relative fitness b. Modeling Selection p = 0.4, q = 0.6 AA Aa aa Parental "zygotes" 0.16 0.48 0.36 = 1.00 prob. of survival (fitness) 0.8 0.4 0.2 Relative Fitness 1 0.5 0.25 Survival to Reproduction 0.24 0.09 = 0.49 Freq’s in Breeding Adults 0.16/0.49 = 0.33 0.24/0.49 = 0.49 0.09/0.49 = 0.18 Gene Frequencies F(A) = 0.575 F(a) = 0.425 Freq’s in F1 (p2, 2pq, q2) 0.33 0.49 0.18 Calculate the gene frequencies, and compute genotypes in offspring (assuming all other HWE conditions are met, like random mating.)

D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: 4. Types of Selection

Intrasexual – competition within a sex for access to mates. D. Deviations From HWE:  5. Natural Selection Fitness Components: Constraints: Modeling Selection: 4. Types of Selection Sexual Selection Some traits that decrease survival may be selected for because they have a direct and disproportional benefit on probability of mating. Intrasexual – competition within a sex for access to mates. Intersexual – mates are chosen by the opposite sex.

Sources of Variation Agents of Change Mutation Natural Selection Modern Evolutionary Biology I. Population Genetics A. Overview B. The Genetic Structure of a Population C. The Hardy-Weinberg Equilibrium Model D. Deviations From HWE E. Summary; The Modern Synthetic Theory of Evolution Sources of Variation Agents of Change Mutation Natural Selection Recombination Genetic Drift - crossing over Migration - independent assortment Mutation Non-random Mating VARIATION