M12 BIO

Evolution

Change in heritable traits over generations.

Sources of Variation

Mutations, sexual reproduction, gene flow, and genetic drift contribute to variations within populations.

Mutations

Random DNA changes that can be beneficial, neutral, or harmful.

Sexual Reproduction

The process that shuffles genes to create genetic variation in offspring.

Gene Flow

The movement of alleles between populations.

Genetic Drift

Random changes in allele frequency that have a larger effect in small populations.

Key Idea of Evolution

Evolution is not goal-directed and complexity does not equal evolutionary advantage.

Evidence for Evolution

Includes DNA analysis, fossil records, homologous structures, and vestigial structures.

Homologous Structures

Structures that have the same origin but different functions, such as limbs of different species.

Vestigial Structures

Leftover traits from ancestors that are no longer used, like the human appendix.

Species

A group of organisms that can interbreed and produce fertile offspring.

Speciation

The formation of new species through genetic isolation and divergence.

Allopatric Speciation

Speciation that occurs due to geographic separation.

Sympatric Speciation

Speciation that occurs without physical barriers, often due to polyploidy or behavioral shifts.

Adaptive Radiation

Rapid speciation to fill different ecological niches.

Prezygotic Barriers

Barriers that occur before fertilization, including temporal, habitat, behavioral, mechanical, and gametic barriers.

Postzygotic Barriers

Barriers that occur after fertilization, such as hybrid inviability, hybrid sterility, and hybrid breakdown.

Hybrid Zones

Regions where different species meet and interact, leading to reinforcement, fusion, or stability.

Speciation Models

Gradualism refers to slow, steady changes, while punctuated equilibrium involves rapid changes followed by long periods of stability.