Mechanisms of Evolution

This section explores the fundamental mechanisms driving evolutionary change, including sexual selection, artificial selection, and natural selection. These processes work together to create adaptations that help organisms survive in their environments.

Vocabulary: Adaptation - A change that makes an organism better suited to survive and reproduce in its environment.

Example: Sexual selection occurs through male-male competition and female choice, where certain traits are selected based on mating preferences.

Highlight: Natural selection requires existing variation in a population and environmental pressures to drive evolutionary change.

Effects of Natural Selection on Populations

Natural selection can affect population phenotypes in three main patterns: directional selection, stabilizing selection, and disruptive selection. Each pattern leads to different distributions of traits within populations.

Definition: Phenotype refers to the observable characteristics of an organism resulting from the interaction of its genotype with the environment.

Example: Directional selection shifts the entire population toward one extreme of a trait, such as longer beaks in finches during drought conditions.

Tenets of Evolution by Natural Selection

The five fundamental tenets of evolution - variation, inheritance, struggle for survival, time, and adaptation - work together to drive evolutionary change in populations.

Definition: Variation refers to the differences among individuals in a population, which arise from genetic mutations and sexual reproduction.

Highlight: Evolution only works on heritable traits that can be passed between generations through genetic inheritance.