Key Concepts in Evolution and Natural Selection

What is evolution?

Changes in allele frequencies in populations, species, or groups over time, driven by natural selection.

What are the two main types of evolution?

Microevolution and macroevolution.

What is microevolution?

Changes in allele frequencies that occur within a population.

What is macroevolution?

Patterns of changes in groups of related species over broad periods of geologic time.

What are the requirements for natural selection?

1. Heritable variation among individuals 2. Competition for resources 3. Accumulation of favorable traits.

What is fitness in the context of evolution?

The ability of an individual to survive and produce fertile offspring.

What is the Hardy-Weinberg equation?

p² + 2pq + q² = 1, used to determine allele frequencies in a population at genetic equilibrium.

What are the five requirements for genetic equilibrium?

1. No mutations 2. No natural selection 3. No gene flow 4. Large population 5. Random mating.

What is genetic drift?

A random increase or decrease of an allele in a population.

What is the founder effect?

A reduction in genetic diversity that occurs when a population is established by a small number of individuals.

What is the bottleneck effect?

A sharp reduction in the size of a population due to environmental events, leading to a loss of genetic diversity.

What are homologous structures?

Body parts that resemble one another between different species that descended from a common ancestor.

What are analogous structures?

Body parts that resemble one another between different species that evolved independently.

What is balanced polymorphism?

The maintenance of different phenotypes in a population.

What is heterozygote advantage?

When heterozygotes have a higher fitness than either homozygous condition.

What is divergent evolution?

The formation of two or more species that descend from a common ancestry and become increasingly different.

What is convergent evolution?

When two unrelated species independently evolve similar traits due to adapting to similar environments.

What is parallel evolution?

When two related species develop similar adaptations after diverging from a common ancestor.

What is coevolution?

When two or more species evolve together in response to new adaptations that appear in another species.

What is speciation?

The formation of a new species, beginning when gene flow ceases between two sections of a population.

What are prezygotic barriers?

Factors that prevent mating or fertilization between species, including habitat, temporal, behavioral, mechanical, and gametic isolation.

What are postzygotic barriers?

Factors that occur after fertilization, including hybrid inviability, hybrid sterility, and hybrid breakdown.

What is allopatric speciation?

Speciation that occurs when a population is divided by a geographic barrier.

What is sympatric speciation?

Speciation that occurs without the presence of a geographic barrier, often through mechanisms like polyploidy or habitat differentiation.