BIOL140 Lectures 6 and 7: Nonadaptive Evolution and Molecular Evolution:

Nonadaptive Evolution: Changes in allele frequencies that do not improve survival or reproduction. Key types include:

• Genetic Drift: Random changes in allele frequencies, especially significant in small populations.

  • Bottleneck Effect: Sudden reduction in population size due to an environmental event, altering genetic diversity.

  • Founder Effect: A new population established by a few individuals from a larger population, leading to reduced genetic variation.

• Migration (Gene Flow): Movement of individuals and their alleles between populations, reducing genetic differences.

• Nonrandom Mating: Preferential mating based on genotype, increasing homozygosity (e.g., inbreeding).

• Mutations: Random changes in DNA, often neutral, but can lead to genetic drift over time.

Examples:

• Northern Elephant Seals: Experienced a bottleneck effect due to hunting, now with low genetic diversity despite population recovery.

• Ellis-van Creveld Syndrome in Amish Communities: A founder effect resulting from a small founding population and inbreeding.

Lecture 7: Molecular Evolution

Molecular Evolution: Studies changes in DNA sequences over time.

• Molecular Clock: Estimates evolutionary time by comparing genetic divergence, calibrated using fossil records.

• Co-evolution: Interactions between species driving mutual evolutionary changes.

• Genetic Divergence: Accumulation of differences in DNA between species over time due to isolation.

Key Concepts:

• Genetic drift can lead to fixation of alleles (frequency = 1).

• Mutations accumulate over generations, contributing to molecular evolution.

• Species concepts used in evolution include biological (interbreeding capability), morphological (appearance), phylogenetic (evolutionary relationships), and ecological (niche occupation).

Case Study – Malaria: Explored human interventions against the Plasmodium parasite through insecticides, drugs, and genetic modification of mosquitos.