Microevolution and Population Genetics

What is microevolution

small-scale changes in allele frequencies within a population over time

What are the four mechanisms of microevolution

mutation, genetic drift, gene flow, natural selection

How do mutations contribute to microevolution

they introduce new genetic variations, which may affect fitness and be acted upon by natural selection

What is genetic drift

random changes in allele frequencies due to chance, especially significant in small populations

What are two types of genetic drift

bottleneck effect and founder effect

Bottleneck effect

sudden reduction in population size due to environmental events

Founder effect

a small group establishes a new population with different allele frequencies

How does gene flow affect populations

the movement of alleles between populations increases genetic diversity and reduced differences between populations

What is the role of natural selection in microevolution

it increases the frequency of beneficial alleles while reducing harmful ones, leading to adaptation

What are the three modes of natural selection

Directional, Stabilizing, Disruptive

Directional Selection

favors one extreme trait

Stabilizing Selection

favors the average phenotype

Disruptive Selection

favors both extreme traits over the average

What is the Hardy-Weinberg equilibrium

principle stating that allele frequencies remain constant if no evolutionary forces act on a population

What are the five conditions for Hardy-Weinberg equilibrium

no mutations, no natural selection, no gene flow, random mating, large population size (no genetic drift)

What is the Hardy-Weinberg equation

p²+2pq+q²=1

What does p represent in the Hardy-Weinberg equation

dominant allele frequency

What does q represent in the Hardy-Weinberg equation

recessive allele frequency

What does p² represent in the Hardy-Weinberg equation

frequency of homozygous dominant individuals

What does 2pq represent in the Hardy-Weinberg equation

frequency of heterozygous individuals

What does q² represent in the Hardy-Weinberg equation

frequency of homozygous recessive individuals

How is the Hardy-Weinberg equation used in population genetics

it helps estimate allele and genotype frequencies in a population to determine if evolution is occuring

What happens if a population does not meet Hardy-Weinberg conditions

evolution is occurring, and allele frequencies are changing over time

What is heterozygote advantage

have higher fitness (sickle cell trait providing malaria resistance)

How does sexual selection drive microevolution

traits that increase mating success become more common, even if they do not directly improve survival