Biology - Chapter 20: Emergence of New Species

speciation

Formation of new species

microevolution

Change in allele frequencies in a population over generations.

macroevolution

Evolutionary change above the species level.

species

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

morphology

Physical traits of an organism

reproductive isolation

Identifies species based on the ability to breed with one another

reproductive isolating mechanisms

Pre and Postzygotic barriers to reproductive success

habitat isolation

(Prezygotic) Unable to reproduce due to differences in habitats

temporal isolation

prezygotic barrier; when different species reproduce at different times

behavioral isolation

prezygotic barrier; the species have differences in mating rituals

mechanical isolation

prezygotic barrier; the species are physically unable to reproduce

gametic isolation

prezygotic barrier; gametes of both parents cannot create a fertilized zygote

hybrid inviability

A postzygotic barrier in which hybrid zygotes fail to develop or to reach sexual maturity

hybrid sterility

postzygotic barrier; the hybrid is infertile

hybrid breakdown

postzygotic barrier; the first-generation hybrids are viable and fertile, but when they mate the offspring are feeble and sterile

interspecies hybrid

when two different species do produce offspring

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

hybrid zones

zones where two different populations can interbreed

reinforcement

Hybrids in the zone are less fit and both breeding populations diverge until no hybrids are produced

fusion

Hybrids are fit and are able to fuse into a single population

stability

Hybrids are produced and reproductive isolation is maintained

sympatric speciation

The formation of new species in populations that live in the same geographic area (Species not split apart)

polyploidy

A chromosomal alteration in which the organism possesses more than two complete chromosome sets.

heterochrony

Evolutionary change in the timing or rate of an organism's development.