Core Concepts
The ultimate source of all new alleles.
Mutation
The type of trait that helps an organism's survival and reproduction.
Adaptation
The sum of all alleles in a population.
Gene Pool
Structures that share a common ancestral form but may have different functions, like a human arm and a cat's leg.
Homologous Structures
The term for the formation of a new species.
Speciation
The type of evolution that involves changes in allele frequency within a population.
Microevolution
The selection type that favors one extreme phenotype in a population.
Directional selection
The name for the condition where allele and genotype frequencies remain constant.
Hardy-Weinberg Equilibrium
A trait that evolved in the common ancestor of a specific group and is unique to that group.
Shared Derived Character or Synapomorphy
Speciation that occurs due to a geographic barrier.
Allopatric Speciation
The geological principle proposed by Lyell that states the same natural processes acted in the past as act now.
Uniformitarianism
The three conditions required for adaptive evolution to occur.
Heritable variation, differential success, consistent pressure
The term for the movement of alleles between populations.
Gene Flow or Migration
The two main lines of evidence scientists use to make evolutionary connections and construct phylogenies.
Morphologic and Genetic
The post-zygotic barrier where a hybrid is born but cannot reproduce.
Hybrid Sterility
The two criteria that define a group of organisms as a single species.
Interbreed and produce fertile offspring
The selection type that maintains variation by selecting against the most common phenotype.
Frequency-Dependent Selection
The type of genetic drift that occurs when a random event like a natural disaster drastically reduces population size.
Bottleneck Effect
The guiding principle for constructing the most probable phylogenetic tree, favoring the simplest path.
Maximum Parsimony
The model of speciation rate characterized by long periods of stasis interrupted by brief periods of rapid change.
Punctuated Equilibrium
The process by which two symbiotic prokaryotic species merge into one, leading to mitochondria and chloroplasts
Genome Fusion
The hypothesis, often associated with elaborate male traits, that suggests an ornament proves the male has "good genes" for survival.
Good Genes Hypothesis
The two mathematical equations used to describe allele and genotype frequencies under Hardy-Weinberg equilibrium.
p+q=1 and p^2+2pq+q^2=1
An evolutionary event that the Web of Life Model and Ring of Life Model explains many shared features of modern organisms in different domains.
Horizontal Gene Transfer or HGT
The two main types of pre-zygotic barriers that prevent fertilization based on timing or location.
Habitat and Temporal Isolation