BIOLOGY2AP-UNIT7EVOLUTIONVOCABULARY

Adaptation

A heritable trait that increases an organism’s fitness in its environment.

Adaptive radiation

Rapid evolution of many species from a common ancestor when new ecological opportunities arise.

Allele

Alternative form of a gene found at a specific locus

Allopatric

Speciation that occurs when populations are geographically separated.

Anagenesis

Evolution within a single lineage without branching (gradual change).

Analogous structure

Body parts with similar function but different evolutionary origins.

Artificial selection

Human-directed breeding for desired traits.

Background extinction rate

Natural, ongoing rate of extinction over time.

Biogeography

Study of species distribution across geographic regions.

Biological species

Specifically, a group of organisms that can interbreed in nature and produce viable, fertile offspring, but are reproductively isolated from other such groups. This is the most common definition used in evolutionary biology but doesn’t apply well to extinct organisms, asexual species, or bacteria.

Cladogenesis

Evolutionary branching where one lineage splits into two or more.

Coevolution

Reciprocal evolutionary changes between interacting species.

Common ancestor

An ancestral species shared by two or more descendant lineages.

Comparative anatomy

Study of similarities and differences in anatomy to infer evolutionary relationships.

Convergent evolution

Independent evolution of similar traits in unrelated lineages due to similar environments.

Darwin

Proposed natural selection as the primary mechanism of evolution.

Fossil

Preserved remains, traces, or impressions of organisms from the past.

Fossil record

Chronological collection of fossils providing evidence for evolution.

Founder effect

Genetic drift that occurs when a new population is started by a few individuals.

Geologic time scale

Timeline dividing Earth’s history into eons, eras, periods, and epochs.

Geology

Study of Earth’s physical structure, processes, and history.

Gene flow

Movement of alleles between populations via migration and interbreeding.

Gene pool

Total collection of alleles in a population.

Genetic bottleneck

Sharp reduction in population size leading to loss of genetic variation.

Genetic drift

Random changes in allele frequencies, strongest in small populations.

Genetic equilibrium

Condition where allele frequencies remain constant across generations.

Genetic variation

Differences in alleles among individuals in a population.

Genotype

Genetic makeup of an organism (allele combination).

Gradualism (anagenesis)

Evolutionary change occurring slowly and steadily over time.

Hardy-Weinberg equation

Mathematical model predicting allele frequencies under no evolution (p²+2pq+q²=1).

Natural selection

Process where individuals with advantageous traits survive and reproduce more successfully.

Paleontology

Study of fossils and ancient life forms.

Panspermia

Hypothesis that life originated elsewhere in the universe and spread to Earth.

Parallel evolution

Similar evolutionary changes in related lineages adapting to similar environments.

Phenotype

Observable traits of an organism, determined by genotype and environment.

Phylogeny

Evolutionary history and relationships among species or groups.

Polymorphism

Occurrence of two or more distinct traits within a population.

Polyploidy

Condition of having more than two complete sets of chromosomes; common in plants.

Population

Group of individuals of the same species living in the same area.

Postzygotic isolating mechanism

Reproductive barrier after fertilization (e.g., hybrid sterility).

Prezygotic isolating mechanism

Reproductive barrier preventing fertilization (e.g., temporal or mechanical isolation).

Primordial environment

Early Earth conditions that allowed the origin of life.

Radiometric dating

Method of determining absolute age of rocks/fossils using radioactive decay.

Random mating

Assumption in Hardy-Weinberg that all individuals are equally likely to mate.

Differential survival

Principle that individuals with favorable traits survive longer and reproduce more.

Directional selection

Natural selection favoring one extreme phenotype.

Disruptive selection

Natural selection favoring both extremes over intermediate traits.

Divergent evolution

Evolution of differences between closely related species due to different environments.

Endosymbiosis

Theory that mitochondria and chloroplasts originated from engulfed prokaryotes.

Epoch

Smallest division of geologic time, part of periods.

Evo-devo

Field studying how developmental processes influence evolution.

Evolution

Change in allele frequencies in a population over generations.

Evolutionary fitness

An organism’s ability to survive and reproduce relative to others.

Extinction

Permanent loss of all members of a species.

Fixation (of alleles)

When an allele’s frequency reaches 100% in a population.

Homologous structures

Similar structures inherited from a common ancestor, possibly with different functions.

Homology

Similarity due to shared ancestry.

Hybrid

Offspring produced by crossing individuals of different species or populations.

Last Universal Common Ancestor (LUCA)

The most recent ancestor from which all modern life descended.

Mass extinction

Rapid, widespread loss of many species across ecosystems.

Migration

Movement of individuals into or out of populations, changing allele frequencies.

Miller-Urey experiments

Classic experiments that simulated early Earth and produced organic molecules.

Modern synthesis

Integration of Darwin’s theory of natural selection with Mendelian genetics.

Molecular clock

Using DNA/protein mutation rates to estimate divergence times.

Mutation

Random change in DNA sequence creating genetic variation.

Relative dating

Determining fossil/rock age by position in strata (older below, younger above).

Reproductive isolation

Barriers that prevent interbreeding between species.

RNA world

Hypothesis that RNA was the first genetic material.

Rock strata

Layers of sedimentary rock used to study Earth’s history.

Speciation

Formation of new species.

Species

A group of organisms that share common characteristics and are classified together. This is a broader term and can be defined in multiple ways (morphological, ecological, genetic, phylogenetic, etc.). For example, paleontologists may classify species based on fossils and morphology alone.

Stromatolite

Layered fossilized microbial mats, among the earliest life evidence.

Sympatric

Speciation occurring without geographic separation.

Transitional fossil

Fossil showing traits of both ancestral and derived species.

Vestigial organ

Structure reduced in function but retained from ancestors.