Honors Biology: Evolution Summative Study Guide

Vocabulary practice flashcards covering Darwinian principles, evidence of evolution, speciation, patterns of macroevolution, and mechanisms of genetic change from the Honors Biology Evolution study guide.

Adaptive Radiation

A form of divergent evolution where a single ancestral species diversifies into multiple distinct ecological forms, such as an ancestral South American finch diversifying into seed crushers, finchlike insect eaters, and warblerlike insect eaters on the Galápagos Islands.

Radiometric Dating

An absolute fossil dating method that calculates the numerical age of a specimen by measuring the remaining quantity and decay rate of radioactive isotopes, such as Carbon-14.

Half-Life

The fixed period of time required for half of the original mass or fraction of a radioactive parent isotope to decay into a stable daughter product.

Relative Age Dating

A method of sequencing geological events and determining whether a fossil or rock layer is older or younger relative to other strata without assigning a numerical age in years.

Homologous Structures

Anatomical features shared by different species that originate from a common ancestor, possessing a similar underlying skeletal architecture despite adapting to perform diverse functions (e.g., the forelimbs of a whale, frog, horse, lion, human, bat, and bird).

Analogous Structures

Biological structures in different organisms that perform similar functions and exhibit superficial similarities due to convergent evolution, but do not share a common evolutionary origin.

Comparative Genomics

A field of molecular biology that provides evidence for evolution by aligning and comparing DNA and gene sequences across different species (such as mouse and fly genes exhibiting $76.66\%$ sequence similarity).

Comparative Embryology

The study and comparison of early anatomical development across organisms, revealing homologous developmental structures—such as gill slits and tails shared by fish, reptile, bird, and human embryos—that are not necessarily retained in adulthood.

Vestigial Structures

Anatomical remnants inherited from ancestral lineages that have lost all or most of their original physiological utility over evolutionary time, such as the pelvis and hind limb bones found in whales.

Cladogram

A branching diagram used in phylogenetic systematics to show hypothetical evolutionary relationships, shared derived traits, and points of most recent common ancestry among different taxa.

Natural Selection

A fundamental evolutionary mechanism in which individuals possessing heritable traits best suited to their environment experience greater survival and reproductive success, increasing the frequency of those traits in future generations.

Artificial Selection

The selective breeding process conducted by humans to intentionally cultivate and propagate specific desirable phenotypic traits in plants and animals.

Sexual Selection

A specific form of natural selection where certain traits increase an organism's success in attracting mates or competing against rivals for mating opportunities.

Directional Selection

A mode of natural selection that favors individuals at one extreme of a phenotypic range, resulting in a directional shift of the population's trait distribution over time.

Disruptive Selection

A mode of natural selection that simultaneously favors individuals at both extremes of a phenotypic distribution while selecting against intermediate phenotypes.

Stabilizing Selection

A mode of natural selection that favors intermediate phenotypes over extreme variations, reducing phenotypic diversity and maintaining the status quo.

Gene Flow

The movement and exchange of genetic alleles between different populations through migration and interbreeding, which prevents genetic divergence between them.

Speciation

The evolutionary lineage-splitting process that gives rise to two or more distinct, reproductively isolated biological species from an ancestral population.

Geographical Isolation

A physical separation of populations by geographic barriers (such as rivers, canyons, or mountain ranges) that disrupts gene flow and initiates independent evolutionary divergence.

Reproductive Isolation

The existence of biological, behavioral, or physiological barriers that prevent members of two populations from interbreeding and producing fertile, viable offspring.

Allopatric Speciation

The mode of speciation that occurs when a physical geographic barrier divides an ancestral population, stopping gene flow and allowing divergent selection and drift to establish reproductive barriers.

Sympatric Speciation

The evolution of new species from a surviving ancestral population occurring in the same geographic region without physical, geographic barriers.

Gradualism

An evolutionary model proposing that species undergo morphological changes and divergence slowly, steadily, and continuously across extensive geological spans of time.

Punctuated Equilibrium

An evolutionary model postulating that long periods of apparent morphological stasis are interrupted by geologically rapid bursts of speciation and significant anatomical transformation.

Divergent Evolution

The macroevolutionary pattern (represented by model A) where two or more distinct descendant species evolve from a single parent species over time due to differing selective pressures.

Convergent Evolution

The evolutionary pattern (represented by model B) where distantly related or unrelated parent species independently evolve analogous phenotypic adaptations when exposed to similar environmental conditions.

Co-evolution

A reciprocal evolutionary process wherein two or more closely interacting species exert selective pressures on each other, evolving adaptations in tandem.

Genetic Drift

A mechanism of evolution caused by unpredictable, random fluctuations in allele frequencies from generation to generation within a population, independent of natural selection.

Founder Effect

A form of genetic drift resulting from the colonization of a new geographical location by a small sub-sample of a population, creating a new gene pool with reduced genetic variation.

Bottleneck Effect

A severe reduction in population size and genetic diversity caused by an abrupt, non-selective catastrophic event or population crash.

Darwin's Principles of Evolution

The core foundational principles—including overproduction of offspring, inherited phenotypic variation, adaptation to selective pressures, and descent with modification—explaining how populations evolve or face extinction over time.