Evolution and Natural Selection Overview

Darwin's Observations and Evolution

• English naturalist Charles Darwin conducted research in the Galapagos Islands, focusing on biogeography.
• He observed that organisms from South America had colonized the Galapagos, evolving into new species.
• Darwin proposed "descent with modification," fundamentally defining evolution as a change in a population's genetic makeup over time.

Evolution and Natural Selection

• Evolution involves hereditary traits passed between generations, changing across generations.
• Natural selection is the process where organisms with beneficial traits are more likely to survive and reproduce.
• Traits are favored because they improve an organism's fitness (ability to survive and reproduce) in their environment.
• The environment exerts selective pressure, influencing reproductive success.
• Examples of selective pressures are environmental shifts like climate change.

Natural Selection Principles

• Heritability: Traits are passed from parents to offspring, driving adaptations.
• Overproduction: More offspring are produced than can survive, creating competition for resources.
• Differential survival: Environmental pressures lead to varied survival rates among individuals.
• Environmental changes affect organism survival rates.

Artificial Selection

• This involves selective breeding in domesticated plants and animals to encourage beneficial traits.

Natural Selection vs. Artificial Selection

• Natural selection is driven by environmental pressures, while artificial selection is directed by human choices.

Population Genetics

• A population is a group of the same species interacting in the same area.
• The gene pool encompasses all genetic variation in a population.
• Fixed alleles indicate lower genetic diversity.

Drivers of Evolution (Microevolution)

• Mutations: Changes in genes that introduce diversity and new alleles. They occur faster in prokaryotes compared to eukaryotes (plants and animals).
• Genetic Drift: Random variations in allele frequencies between generations, significant in small populations.
• Bottleneck effect: Population reduction due to a disaster.
• Founder effect: A new population derived from a small, isolated group.
• Gene Flow: Allele transfer between populations, like pollen transfer.
• Natural Selection: Three types – directional, stabilizing, and disruptive.
• Sexual selection: explains unique traits chosen by mate preference.

Hardy-Weinberg Equilibrium

• It's a model used to assess evolution in populations.
• It describes the genetic makeup of a non-evolving population.
• Five conditions need to be met for the equilibrium to apply: No mutations, random mating, no selection, unlimited population size, and no gene transfer.
• If any condition is violated, microevolution occurs.
• The formula is p + q = 1 and p² + 2pq + q² = 1.