AP Bio Unit 7 Natural Selection

Evolution

Change in the genetic makeup of a population over time

Natural Selection

Process where individuals with advantageous traits survive and reproduce more

Adaptation

Heritable trait that increases fitness

Fitness

Ability to survive and produce fertile offspring

Selective Pressure

Environmental factor that influences survival and reproduction

Artificial Selection

Human-directed breeding for desired traits

Population

Group of interbreeding individuals of the same species

Gene Pool

Total genetic makeup of a population

Allele Frequency

Proportion of a specific allele in a population

Microevolution

Small-scale changes in allele frequencies

Mutation

Primary source of genetic variation

Genetic Drift

Random change in allele frequencies

Bottleneck Effect

Sharp reduction in population size causing loss of variation (e.g. due to natural disasters)

Founder Effect

New population established by a small group of individuals

Gene Flow

Movement of alleles between populations

Directional Selection

Selection favoring one extreme phenotype

Stabilizing Selection

Selection favoring the average phenotype

Disruptive Selection

Selection favoring extreme phenotypes

Sexual Selection

Selection based on mating success

Hardy-Weinberg Equilibrium

Model describing non-evolving populations

Hardy-Weinberg Conditions

No mutation, random mating, no selection, large population, no gene flow

p + q = 1

Equation representing allele frequencies

p² + 2pq + q² = 1

Equation representing genotype frequencies

Fossil Record

Preserved remains or traces of past life

Homologous Structures

Structures with shared ancestry but different functions

Analogous Structures

Structures with similar function but different ancestry

Vestigial Structures

Reduced structures with little or no function

Convergent Evolution

Independent evolution of similar traits

Divergent Evolution

Accumulation of differences from a common ancestor

Biogeography

Study of species distribution

Phylogeny

Evolutionary history of a species

Cladogram

Diagram showing evolutionary relationships

Node

Branch point representing a common ancestor

Clade

Group consisting of a common ancestor and all descendants

Synapomorphy

Shared derived trait

Outgroup

Species used for comparison outside the study group

Speciation

Formation of a new species

Reproductive Isolation

Prevention of gene flow between populations

Prezygotic Barriers

Prevent mating or fertilization

Postzygotic Barriers

Prevent hybrid viability or fertility

Allopatric Speciation

Speciation caused by geographic isolation

Sympatric Speciation

Speciation without geographic isolation

Punctuated Equilibrium

Rapid evolution following long periods of stasis

Gradualism

Slow, continuous evolutionary change

Extinction

Elimination of a species