Overview
This topic explains the mechanisms behind evolution and how species arise. It covers natural selection, genetic variation, evidence for evolution, and the processes that lead to the formation of new species over time.
Key Concepts and Structures
- Evolution: The change in genetic makeup of populations over generations. Driven by mechanisms like mutation, natural selection, gene flow, and genetic drift.
- Natural Selection: Individuals with traits better suited to their environment tend to survive and reproduce, passing on those traits. "Survival of the fittest."
- Adaptation: A heritable trait that increases an organism’s fitness in a particular environment.
- Genetic Variation: Comes from mutations, recombination, and sexual reproduction. Essential for evolution to occur.
- Evidence of Evolution: Includes fossil records, comparative anatomy (homologous structures), embryology, molecular similarities, and observed changes.
- Speciation: The formation of new species from existing ones, often through reproductive isolation. Includes allopatric (geographic separation) and sympatric (non-geographic) speciation.
- Reproductive Isolation: Prevents gene flow between populations. Includes prezygotic barriers (e.g., behavioral isolation) and postzygotic barriers (e.g., infertile offspring).
- Genetic Drift: Random changes in allele frequencies, especially in small populations. Includes bottleneck and founder effects.
- Gene Flow: Movement of alleles between populations through migration. Increases genetic diversity.
- Evolutionary Trees: Diagrams (phylogenies) that show evolutionary relationships based on shared traits and common ancestry.
Quick Tip
Focus on the difference between natural selection and genetic drift. Be able to explain how reproductive isolation leads to speciation and how scientists use evidence to support evolutionary theory.