Key Concepts in Evolution and Natural Selection

Evolution

Any change over time in the genes of a population.

Populations and Individuals

Populations evolve over time; individual organisms do not.

Natural Selection

Process where individuals with favorable traits survive and reproduce more ('survival of the fittest').

Gene Pool

All the genes present in a population.

Allele Frequency

The number of times a particular allele occurs in a gene pool.

Genetic Drift

Random changes in allele frequency in a population.

Bottleneck Effect

Genetic drift caused by a drastic reduction in population size.

Founder Effect

Genetic drift caused when a small group starts a new population with different allele frequencies.

Gene Flow

Gain or loss of alleles due to individuals moving in or out of a population.

Natural Selection vs Genetic Drift and Gene Flow

Natural selection is based on fitness; genetic drift and gene flow are based on chance.

Speciation

The process where one species splits into two or more new species.

Species Definition

A group of organisms that can breed and produce fertile offspring.

Reproductive Isolation

Occurs when two populations cannot interbreed and produce fertile offspring.

Mechanisms of Reproductive Isolation

Geographic, ecological, temporal, behavioral, and mechanical isolation.

Geographic Isolation

Physical barriers separate populations.

Ecological Isolation

Populations live in different habitats in the same area.

Temporal Isolation

Species reproduce at different times.

Behavioral Isolation

Differences in mating behaviors prevent reproduction.

Mechanical Isolation

Physical differences prevent mating.

Gradualism

Slow, constant evolutionary change.

Punctuated Equilibrium

Rapid evolution followed by long periods of no change.

Carl Linnaeus

Swedish botanist who developed binomial nomenclature and hierarchical classification.

Binomial Nomenclature

Scientific naming system with genus and species names (e.g., Homo sapiens).

Levels of Classification

Species, genus, family, order, class, phylum, kingdom.

Dichotomous Key

A tool used to identify organisms based on a series of choices.

Phylogeny

The study of evolutionary relationships between organisms.

Cladogram

A diagram showing evolutionary relationships via branching lines.

Biogeography

The study of the distribution of organisms now and in the past.

Fossil Record

They show a historical sequence of organism appearance and changes over time.

Homologous Structures

Similar structures in different species inherited from a common ancestor.

Divergent Evolution

When related species evolve different traits due to different environments.

Analogous Structures

Structures with similar functions but different ancestry.

Convergent Evolution

When unrelated species evolve similar traits due to similar environments.

Vestigial Structures

Remnants of structures that were important in ancestors.

Comparative Embryology

Similar embryonic development patterns show common ancestry.

Molecular Biology

Similarities in genetic code show shared ancestry among organisms.