AP BIO - unit 7: Natural selection

Biogeography

Study of species distribution across geographic areas

Evolution

Change in genetic makeup of a population over time

Descent with modification

Species change over generations from common ancestors

Natural selection

Process where individuals with favorable traits survive and reproduce

Fitness

Ability of an organism to survive and reproduce

Competition

Struggle between organisms for limited resources

Biotic factors

Living components of an environment

Abiotic factors

Nonliving components of an environment

Selective pressures

Environmental factors that influence survival

Adaptations

Traits that improve survival and reproduction

Phenotype

Observable traits of an organism

Genotype

Genetic makeup of an organism

Mutation

Change in DNA sequence

Population

Group of same species living in an area

Gene pool

All genes in a population

Fixed

When an allele frequency reaches 100% in a population

Genetic drift

Random change in allele frequencies

Bottleneck effect

Reduction in population size leading to loss of variation

Founder effect

New population started by small group with limited variation

Gene flow

Movement of alleles between populations

Directional selection

Favors one extreme phenotype

Stabilizing selection

Favors intermediate phenotypes

Disruptive selection

Favors extreme phenotypes at both ends

Sexual selection

Selection based on mating success

Hardy-Weinberg equilibrium

State where allele frequencies do not change

Comparative morphology

Study of similarities in body structures

Analogous structures

Structures with similar function but different origin

Embryonic homology

Similarities in embryo development

Vestigial structure

Reduced structure with no current function

Molecular homology

Similarities in DNA or protein sequences

Homologous structures

Structures with common ancestry but different function

Common ancestor

Shared ancestor of multiple species

Convergent evolution

Independent evolution of similar traits

Homology

Similarity due to shared ancestry

Fossil

Preserved remains of organisms

Node

Point on a phylogenetic tree representing common ancestor

Cladograms

Diagrams showing evolutionary relationships

Phylogenetic tree

Diagram showing evolutionary history

Systematics

Study of evolutionary relationships

Basal taxon

Lineage that diverged early

Sister taxa

Two groups sharing a recent common ancestor

Monophyletic group

Group containing ancestor and all descendants

Derived characteristic

Trait that evolved recently

Ancestral characteristic

Trait inherited from distant ancestor

Synapomorphy

Shared derived characteristic

Paraphyletic group

Includes ancestor but not all descendants

Polyphyletic group

Group without common recent ancestor

Taxonomy

Classification of organisms

Phylogenetics

Study of evolutionary relationships

Root

Base of a phylogenetic tree

Outgroup

Group used for comparison in a phylogenetic tree

Parsimony

Simplest explanation with fewest changes

Species

Group that can interbreed and produce fertile offspring

Speciation

Formation of new species

Geography

Physical location affecting species distribution

Temporal isolation

Reproduction occurs at different times

Prezygotic barrier

Prevents fertilization

Postzygotic barrier

Occurs after fertilization

Sympatric speciation

Speciation without geographic separation

Behavioral isolation

Differences in mating behaviors

Mechanical isolation

Physical incompatibility of reproductive structures

Reduced hybrid viability

Offspring do not develop properly

Reduced hybrid fertility

Offspring are sterile

Punctuated equilibrium

Rapid bursts of evolution with little change between

Macroevolution

Large-scale evolutionary changes

Hybrid breakdown

Offspring viable but weak or sterile in later generations

Gradualism

Slow and steady evolution over time

Divergent evolution

Species become more different over time

Convergent evolution

Unrelated species develop similar traits

Allopatric speciation

Speciation due to geographic separation

Gametic isolation

Gametes cannot fuse

Microevolution

Small changes in allele frequencies

Adaptive radiation

Rapid diversification into many species

Habitat isolation

Species live in different habitats

Extinction

Loss of a species

RNA world hypothesis

Early life based on RNA as genetic material