Evolution and Natural Selection

Charles Darwin

Proposed the Theory of Natural Selection

Disruptive selection

Type of selection in which the fitness of individuals at the extreme ends higher than that of individuals in the middle

Natural selection

Factors in the environment cause organisms to change over time

Artificial selection

Man selects which traits to breed for the outcome

Fitness

Measure of how suited an organism is for its habitat

Gene pool

All the genes belonging to a species in the same breeding group

Allele frequency

How often an allele for a trait appears in a gene pool

Genetic drift

Altering of allelic frequencies by chance

Founders effect

Gene pool only contains the alleles of the species first to arrive on an island

Bottleneck effect

Dramatic population reduction leaves only some alleles in the gene pool

Gene flow

Affect on allele frequencies based on movement of individuals from one population to another

Variation

Inheritable differences within a species

Adaptive radiation

One species evolves into many species

Divergent evolution

species differ in appearance but are structurally similar

Convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

Co-evolution

Two or more species influence each other's evolution

Punctuated equilibrium

Speciation takes place in short, fast bursts

Homologous structures

Structures that have the same structure but different functions

Analogous structures

Body parts that share a common function but not structure

Vestigial structures

Remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.

Stabilizing selection

Type of selection in which the fitness of individuals in the middle higher than that of individuals at the extreme ends

Directional selection

Type of selection in which the fitness of individuals at one end of the normal distribution curve higher than that of individuals in the middle or at the other end of the curve