Natural Selection

• Process where organisms better adapted to environment survive & produce more offspring than competitor • Leads to evolution

Development of life into current diversity of organisms

• Random assortment of paternal & maternal chromosomes in meiosis • Crossing over of segments of homologous chromosomes • Random fusion of male & female gametes • Mutations

• Environmental factor affecting survival & reproduction of organisms • Biotic/abiotic

Organism’s ability to pass genetic material to offspring

• Selection made by preference of one sex for certain characteristics in indivduals of other sex • Can cause sexual dimorphism

All genes (& their alleles) present in a breeding population

Directional: population shifts → extreme phenotype Stabilizing: favors intermediate phenotype Disruptive: favours both extremes

Proportion of specific allele in population’s gene pool

Selective breeding of organisms by humans for desired traits

Inherited characteristic increasing organism’s survival & reproductive success in specific environment

Organisms overproduce offspring → Limited resources → competition → survival of the fittest → natural selection

Traits → fitness → reproductive success → allele frequency change → evolution

Random change in allele frequencies in a population (no natural selection)