Evolution, Selection, and Speciation Vocabulary Flashcards

Vocabulary flashcards covering modes of natural selection, species concepts, mechanisms of speciation, and evolutionary rate models based on the lecture notes.

Directional selection

Selection for one extreme trait and against the other extreme, causing a population trait shift such as moth color shifting from light to dark in sooty environments during nineteenth-century England.

Stabilizing selection

Selection for moderate traits and against both extremes, such as human birth weight survival rates or robins typically laying $4$ eggs to avoid malnourished chicks or unviable offspring.

Disruptive selection

Selection for both extremes of a trait and against moderate traits, such as large and small bird beaks outperforming medium beaks, or gray and Himalayan rabbits blending better in rocky environments than white rabbits.

Species

A group of organisms that actually or potentially inbreed in nature.

Infertility between species

The inability of hybrid offspring (such as sterile mules from horses and donkeys) to reproduce, usually resulting from parents having different numbers of chromosomes, which makes meiosis impossible.

Speciation

The formation of new species through reproductive isolation.

Allopatric speciation

Speciation resulting from physical separation by geographic barriers, such as mountain ranges or rivers, that prevent populations from meeting and interbreeding.

Sympatric speciation

Speciation resulting from ecological separation, where interbreeding is prevented by factors such as feeding at different times or having different mating behaviors.

Gradualism

An evolutionary model proposing that evolution occurs through the slow and steady accumulation of changes over time.

Punctuated equilibrium

An evolutionary model proposing that evolution occurs in rapid bursts after long periods with no morphological change.