Chapter 17 biology

Genetic Variation

Differences in alleles within a population, caused by mutations, sexual reproduction, and environmental factors.

Independent Assortment

The random distribution of chromosomes during meiosis, leading to genetic variation.

Crossing Over

The exchange of genetic material between homologous chromosomes during meiosis, creating new allele combinations.

Phenotype

The observable traits of an organism, resulting from the interaction of its genotype and environment.

Discontinuous Variation

Phenotypic variation where characteristics fall into distinct categories with no intermediates.

Continuous Variation

Phenotypic variation where characteristics show a range of values without distinct categories.

Polygenic Inheritance

Traits controlled by multiple genes, each contributing a small effect to the phenotype.

Founder Effect

A reduction in genetic variation occurring when a small number of individuals establish a new population.

Bottleneck Effect

A dramatic reduction in population size that decreases genetic diversity, often due to environmental events.

Natural Selection

The process by which individuals with advantageous traits are more likely to survive and reproduce.

Directional Selection

Natural selection that favors individuals at one extreme of a trait distribution.

Stabilizing Selection

Natural selection that favors average traits and reduces variation.

Disruptive Selection

Natural selection that favors individuals at both extremes of a trait distribution.

Gene Flow

The transfer of alleles from one population to another, which can alter allele frequencies.

Mutation

A change in the DNA sequence which may introduce new alleles into a population.

Reproductive Isolation

The inability of different populations to interbreed, leading to speciation.

Allopatric Speciation

Speciation that occurs due to geographical isolation of populations.

Sympatric Speciation

Speciation that occurs without geographical isolation, often through behavioral barriers.

Hardy-Weinberg Principle

A model that describes gene frequencies in a population that is not evolving.

Artificial Selection

The human practice of breeding animals or plants for specific traits.

Genetic Drift

Random changes in allele frequencies in a population, significant in small populations.

Selection Pressure

An environmental factor that influences which traits are favorable for survival and reproduction.

Hybrid Vigor

Increased biological productivity due to a cross between genetically distinct individuals.

Fitness

An organism's ability to survive and reproduce in its environment.