Chapter 13: How Populations Evolve (Honors Biology Grasso)

Strata

Layers of sedimentary rock formed by compression over time that entomb fossils and establish historical chronological order.

Homology

Similarity in anatomical or molecular characteristics between different species resulting from shared common ancestry.

Homologous Structures

Anatomical features that have different functions in different organisms but share an underlying structural framework inherited from a common ancestor.

Vestigial Structures

Remnants of anatomical features that served important functions in ancestral organisms but have little to no utility in modern descendants.

Natural Selection

An evolutionary mechanism where individuals with specific heritable traits survive and reproduce at higher rates than others, increasing the frequency of adaptive traits over generations.

Artificial Selection

The intentional selective breeding of domesticated animals and plants by humans to enhance desirable phenotypic traits.

Microevolution

A change in the frequencies of alleles within a population gene pool over generations.

Gene Pool

The total aggregate of every allele at every locus across all individuals in a population.

Five conditions of Hardy-Weinberg equilibrium

A very large population size, absence of gene flow, no net mutations, random mating, and no natural selection.

Hardy-Weinberg equations

p²+2pq+q²=1, where p² represents homozygous dominants, 2pq represents heterozygotes, and q² represents homozygous recessives.

Genetic Drift

Unpredictable fluctuations in allele frequencies from generation to generation driven by chance events, impacting small populations most severely.

Bottleneck Effect

A drastic reduction in population size caused by environmental catastrophes or human activity that leaves a surviving gene pool with altered allele frequencies.

Founder Effect

A form of genetic drift resulting from a small group establishing an isolated colony, leading to allele frequencies distinct from the source population.

Gene Flow

The movement of fertile individuals or gametes into or out of a population, reducing genetic divergence between populations.

Relative Fitness

The proportional contribution an individual makes to the gene pool of the subsequent generation compared to other members.

Directional Selection

A mode of natural selection that shifts phenotypic distribution by favoring one extreme variation over others.

Stabilizing Selection

A mode of natural selection that favors intermediate variants by acting against extreme phenotypes.

Disruptive Selection

A mode of natural selection favoring organisms at both ends of the phenotypic spectrum while selecting against intermediate traits.

Sexual Dimorphism

Marked differences in secondary sexual characteristics, such as size or ornamentation, between males and females of the same species.

Hetrozygote Advantage

A form of balancing selection where heterozygous individuals experience higher reproductive success than either homozygote, maintaining multiple alleles.

Sexual Evolution

Type of natural selection where organisms with specific traits have a better chance of finding a mate, causing males and females to look different and eventually splitting them into new species.

Phenotypic Plasticity

An organism changes its body, behavior, or how it works to survive in a new environment, without changing its DNA.

Intersexual Selection

Competition between members of the same sex (usually males) for access to the opposite sex

Intrasexual Selection

Members of one sex (usually females) choosing partners based on specific attractive traits or displays.

Cetacean

A group of seawater mammals such as dolphins and whales.

Fossils

Imprint or remain of an organism that lived in the past

Evolutionary Tree

Diagram representing patterns of descent from common ancestors

Variation

Individuals within a population differ in their traits.

Heritability

Traits are passed from parents to offspring.