Mechanism of Evolutionary Change

"MECHANISM OF

EVOLUTIONARY CHANGE"

NATURAL SELECTION

Survival of the fittest

Related to the principle of descent with modification

Concept of fitness is the central process of evolution

DISRUPTIVE SELECTION

DIRECTIONAL SELECTION

STABILIZING SELECTION

- occurs when selective pressures are working in favor of the two extremes and against the intermediate trait.

- occurs when there are selective pressures working against two extremes of a trait and therefore the intermediate or “middle” trait is selected for frequency.

- occurs when selective pressures are working in favor of one extreme of a trait.

ARTIFICIAL SELECTION

Selective breeding

Artificial selection is the identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations

GENETIC DRIFT

Occurs in all populations of non-infinite size, but its effects are strongest in small populations

Change in allele frequencies in a population from generation to generation that occurs due to chance events

POPULATION BOTTLENECK

FOUNDER EFFECT

- a sharp reduction in the size of a population due to environmental events (flooding, earthquake, etc.)

- occurs when a small group of individuals breaks off from a larger population to establish a colony.

MUTATION

Any change in a sequence of DNA caused by mistakes during replication or environmental factors

Can be beneficial, harmful, or harmless

DUPLICATION

TRANSLOCATION

DELETION

- occurs when a section of a chromosome is added from its homologous partner.

- is where a section of a chromosome is added to another chromosome that is not its homologous partner.

- is where a section of a chromosome is removed.

RECOMBINATION

Rearrangement of genes

A process by which pieces of DNA are broken and recombined to produce new combinations of alleles.

Naturally occurs during the crossing over stage in meiosis