The Evolution of Populations and Hardy-Weinberg Principle

Darwin's Theory

Evolution based on genetic variation.

Mendelian Genetics

Supports Darwin's theory of evolution.

Discrete Characters

Classified on an either-or basis.

Quantitative Characters

Vary along a continuum within populations.

Microevolution

Change in allele frequencies over generations.

Point Mutations

Changes in one DNA base.

Chromosomal Mutations

Alterations in chromosome structure.

Sexual Recombination

Main contributor to genetic variation.

Crossing Over

Exchange of genetic material during meiosis.

Independent Assortment

Random distribution of chromosomes during meiosis.

Gene Pool

All alleles for all genes in a population.

Diploid Species

Have two alleles for each gene.

Fixed Allele

Only one allele present in a population.

Hardy-Weinberg Principle

Allele frequencies remain constant without evolution.

Equilibrium

Constant allele and genotype frequencies.

Hardy-Weinberg Conditions

No mutations, random mating, no selection.

Allele Frequencies

Proportions of alleles in a population.

Genotypic Frequencies

Proportions of different genotypes in a population.

p

Frequency of dominant allele.

q

Frequency of recessive allele.

p²

Frequency of homozygous dominant genotype.

2pq

Frequency of heterozygous genotype.

q²

Frequency of homozygous recessive genotype.

Calculating q

Square root of homozygous recessive individuals.

Founder Effect

Small group isolated from larger population.

Bottleneck Effect

Population size drastically reduced by environmental change.

Gene Flow

Movement of individuals between populations.

Natural Selection

Survival of individuals with favorable traits.

Directional Selection

One extreme phenotype favored.

Disruptive Selection

Both extreme phenotypes favored.

Stabilizing Selection

Intermediate phenotype favored.

Sexual Selection

Individuals with certain traits more likely to mate.

Sexual Dimorphism

Differences in appearance between sexes.

Intrasexual Selection

Competition within the same sex.

Intersexual Selection

Mate choice by the opposite sex.

Diploidy

Hides recessive alleles in heterozygotes.

Heterozygote Advantage

Higher fitness than homozygous individuals.

Historical Constraints

Evolution limited by past adaptations.

Genetic Variation Preservation

Maintaining diversity in a population.

Sickle Cell Disease

Example of heterozygote advantage.

Genotype Frequencies Calculation

Using p and q to find frequencies.

Phenotypic Variation

Differences in observable traits among individuals.

Evolutionary Compromises

Adaptations often involve trade-offs.

Sample Problem

Determine allele and genotype frequencies.

Scarlet Moth Example

Calculate frequencies in a population of moths.

Albinism in Squirrels

Example of calculating allele frequencies.

Mice Population Example

Calculate genotype frequencies from given data.