Evolutionary Processes

Natural Selection

Certain alleles increase in frequency because they improve survival or reproduction.

Genetic Drift

Random changes in allele frequencies, especially significant in small populations

Gene Flow

Movement of alleles between populations due to migration, introducing new genetic material.

Mutation

New alleles arise from random changes in DNA, providing raw material for evolution.

Non-random mating

Individuals select mates based on traits, affecting which alleles get passed on

Directional Selection

Favors one extreme phenotype, shifting the population’s traits in one direction (e.g., antibiotic resistance).

Stabilizing Selection

Favors intermediate phenotypes and reduces variation (e.g., human birth weights).

Disruptive Selection

Favors both extreme phenotypes over intermediates, potentially leading to two distinct groups (e.g., beak sizes in birds where medium-sized beaks are less advantageous)

outline process of speciation

1. Isolation: A population becomes split (geographically or reproductively).

2. Genetic Divergence: Different selective pressures, mutations, or genetic drift cause genetic differences to build up between the isolated groups.

3. Reproductive Isolation: Over time, the groups can no longer interbreed even if they come back together.

4. Speciation: New distinct species are formed.

Allopatric Speciation

Geographic speciation

Sympatric Speciation

New species arise within the same geographic area, often through behavioral or genetic changes