Populations

Population

A group of organisms of the same species living in the same area at the same time that can interbreed

Gene pool

The total number of alleles present in a population

Allele frequency

The proportion of a specific allele in a gene pool expressed as a decimal or percentage

Hardy-Weinberg principle

Used to estimate allele frequencies and determine if they change over time

Purpose of Hardy-Weinberg

To identify whether evolution is occurring in a population

Hardy-Weinberg assumption

No mutations occur to create new alleles

Hardy-Weinberg assumption

No natural selection so all alleles have equal chance of being passed on

Hardy-Weinberg assumption

No migration into or out of the population

Hardy-Weinberg assumption

The population is large

Hardy-Weinberg assumption

Mating is random

Hardy-Weinberg equation p + q

p + q = 1

Hardy-Weinberg genotype equation

p² + 2pq + q² = 1

p

Frequency of the dominant allele

q

Frequency of the recessive allele

p²

Frequency of homozygous dominant genotype

2pq

Frequency of heterozygous genotype

q²

Frequency of homozygous recessive genotype

Genetic variation

Differences in alleles between individuals of the same species

Random fertilisation

Gametes carrying different alleles fuse randomly

Meiosis

Creates genetic variation by random assortment of alleles

Mutation

Changes in DNA that can create new alleles

Environmental variation

Differences in phenotype caused by environmental factors

Example of environmental influence

Soil mineral availability affecting flower colour

Continuous variation

Phenotypic variation showing a range of values

Continuous variation example

Human height

Distribution of continuous variation

Normal distribution curve