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Biology Ch 24

The Origin of Species

Side 1Side 2
speciation The process by which one species splits into two or more species
reproductive isolation The existence of biological factors (barriers) the impede members of two species from producing viable, fertile offspring
allopolyploid A fertile individual that has more than two chromosomes sets as a result of two different species interbreeding and combining their chromosomes
hybrid Offspring that results from the mating of individuals from two different varieties of the same species
reinforcement A process in which natural selection strengthens prezygotic barriers to reproduction, thus reducing the chances of hybrid formation. Such a process is likely to occur only if hybrid offspring are less fit than members of the parent species
microevolution Evolutionary change below the species level; change in the allele frequencies in a population over generations
fusion A process in which gene flow between two species that can form hybrids offspring weakens barriers to reproduction between the species. This process causes genepools to become increasingly alike and can cause the two species to fuse into a single species.
punctuated equilibria In the fossil record, long periods of apparent stasis, in which a species undergoes little or now morphological change, interrupted by relatively brief periods of sudden change.
biological species concept Definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not produce viable, fertile offspring of members of other such groups.
macroevolution Evolutionary change above the species level. Examples: the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery.
morphological species concept Definition of a species in terms of measurable anatomical criteria.
postzygotic barrier A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults.
hybrid zone A geographic region in which members of a different species meet and mate, producing at least some offspring of mixed ancestry
autopolyploid An individual that has more than two chromosomes sets that are all derived from a single species
sympatric speciation The formation of new species in populations that live in the same geographic are.
allopatric speciation The formation of new species in populations that are geographically isolated from one another
ecological species concept Definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.
prezygotic barrier A reproductive barrier that impedes mating between species of hinders fertilization if interspecific mating is attempted
polyploidy A chromosomal alteration in which the organism posses more than two complete chromosome sets. It is the result of an accident of cell division.
habitat differentiation A form of sympatric speciation in which a subpopulation exploits a habitat or resource not used by the parent population.
stability A hybrid zone that continues to produce hybrids.
paleontological speciation concept Definition of species in terms of morphology known only from the fossil record.
phylogenetic species concept Definition of species in terms of shared ancestors using morphological and molecular characteristics.
Created by: jabflat