Principios de Taxonomia

Allopatric speciation proceeds without selective pressure and requires no pre- or
postzygotic mating barriers, and therefore it is the result of pure coincidence
Speciation, sympatric Speciation under conditions in which individuals encounter
each other regularly during the process of speciation. As sympatric speciation is the
origination of two new species at the same location; this process requires prezygotic
mating barriers to arise that are supported by selection.
Speciation gene A gene that is responsible for keeping two groups of organism
separate from each other via preventing successful cross-breeding. Speciation genes
encode the traits that are responsible for pre- or postzygotic barriers.
Species A group of organisms separated from another group of organisms via
external or internal barriers that interrupt gene flow between the organisms. External
barriers are usually geographic barriers (allopatry). Internal barriers are prezygotic or
postzygotic incompatibilities. Phylogenetic distance alone cannot define a species
because a species definition requires that the cohesive connection between the
members of two species is broken.
Species, cryptic Two or more different species with (almost) identical traits.
Species, polytypic A species consisting of different morphs.
Species definition The ontological definition of a species. The criteria determining
how two species can be distinguished from each other are not sufficient to act as a
species definition.
Species identification The procedure for distinguishing two species from each
other on the basis of particular identification traits. Species identification is a
diagnostic procedure and is not the same as species definition.
Stem species A species in the cladistic tree prior to its division into two daughter
species.
Subspecies Synonymous with race.
Sympatry/sympatric distribution The occurrence of two populations that
encounter each other regularly at the same location. Sympatric distribution is
only possible if the individuals of the two populations possess mating barriers
that prevent hybrid formation (see pre- and postzygotic barriers). Allopatric
distribution is the opposite.
Taxon A group of organisms that is useful for taxonomic classification.
Taxonomy The science of combining organisms into groups.
Scientific Terms j237
Transcription factor A protein that regulates the time and intensity of the
expression of a corresponding gene by binding to an enhancer (see enhancer).
Uniparental reproduction The production of offspring from only one parent. This
can occur via self-fertilization, parthenogenesis or vegetative reproduction. There is
no sexual contact between males and females under this scenario.