Principios de Taxonomia

234j Scientific Terms
Monophylum A cladistic group of taxa that includes all of the descendants of a most
recent common ancestor (Figure 7.5) (see paraphylum).
Morph Diagnostically distinct group of organisms within a species at the same
location that interbreed without producing viable phenotypic intermediates. The best
example of this is males and females (sexual dimorphism). Morphs must have
different genotypes, and are thus distinguished from phenotypically different
developmental stages, such as larvae in contrast to adults or seasonal di- or
polymorphisms (see race).
Morpho-species A formal species concept that combines all organisms into a group
that possess equal or similar morphological traits.
Natural kind A class of objects sharing equivalent traits of which at least one trait is
essential, meaning that it is necessary and sufficient for class membership. If this
essential trait is missing in a particular object, this object cannot member of the class,
and if there is any object in the world that possesses this essential trait, this object
must by definition belong to the group. Natural kinds are considered to actually exist
in nature, in contrast to artificial classes, which are combinations of objects produced
by human sorting efforts. The best example of natural kinds is the chemical elements,
whose group affiliation is based on atomic number. In contrast, biological species are
not natural kinds because there are no traits that are necessary and sufficient for
species membership.
Neutral DNA sequence A DNA sequence that is not the target of selection.
Orthologous and paralogous genes Orthologs are alleles (alloforms) of a particular
gene that arise during mitotic replication of the genome during mitosis. Paralogs
(isoforms) of a particular gene are the result of gene duplication. All orthologous
genes occupy the same chromosomal locus within the genomes of all organisms in a
population, whereas paralogous genes occupy different loci in the genome. If
homologous DNA sequences are aligned between different organisms, it is
important to distinguish between orthologous homology and paralogous homology.
Paraphylum A cladistic group of taxa that includes only a subset of the descendants
of a most recent common ancestor. Evolutionarily younger branches are excluded and
classified as separate groups with the same rank as the rest of the cladistic group
(Figure 7.5). The best-known example of a paraphylum is the class of reptiles, from
which the subgroup of birds has been removed and designated as a separate class
(Figure 7.6) (see monophylum).
Parthenogenesis Production of offspring from an unfertilized egg.
Parthenogenetic reproduction is reproduction without a father. In contrast to
vegetative reproduction, however, it is a type of sexual reproduction because the
offspring arises from a germ cell.
Partially migratory birds A polymorphic population of birds in which the migratory
and sedentary morphs of a bird species live together in an overlapping transitory
region. One subset of the birds leaves the breeding habitat in fall and returns again in