BIO 112 Exam 3 Speciation

biological species concept

species defined by reproductive isolation

morphospecies concept

species identified by differences in morphological (physical) features; assumes unique features arise if populations are genetically independent

phylogenetic species concept

species defined as the smallest monophyletic group on the tree of life, identified by synapomorphies (shared derived traits)

prezygotic isolation

barriers that prevent mating or fertilization from occurring

postzygotic isolation

barriers where zygotes are produced but offspring do not survive or are sterile

temporal isolation

populations are isolated because they breed at different times

habitat isolation

Populations are isolated because they occupy different habitats

behavioral isolation

Populations do not interbreed due to differences in courtship behaviors

mechanical isolation

Mating fails because male and female reproductive structures are incompatible

gametic isolation

Mating fails because sperm and egg are incompatible

hybrid inviability

Hybrid offspring do not develop normally and die early

hybrid sterility

Hybrid offspring survive but are sterile as adults

allopatric speciation

Speciation that occurs when populations are geographically separated, preventing gene flow

dispersal

Individuals move to a new area, become isolated, and diverge

vicariance

A physical barrier separates a population, leading to genetic isolation and divergence

sympatric speciation

Speciation that occurs without geographic isolation; populations become isolated within the same area

disruptive selection

Natural selection that favors individuals at both extremes, increasing differences between populations

niche (ecological niche)

The range of ecological resources or conditions a species can use or tolerate

fusion

Two populations freely interbreed and merge into one population

extinction

One population is outcompeted and eliminated

reinforcement

Natural selection increases reproductive isolation because hybrid offspring have low fitness

hybrid zone

A geographic area where hybridization occurs between populations

hybrid speciation

Hybrid offspring occupy a distinct habitat or use novel resources and form a new species