Principios de Taxonomia

232j Scientific Terms
Gene-flow community A group of organisms that are cohesively connected via
sexual gene flow. This means that the organisms or their descendants exchange genes
through occasional sexual contact with each other, and their genomes recombine
(Figure 2.7). Sexual lateral gene flow disturbs a dichotomous phylogenetic tree by
replacing it through a network of bypasses between branches (Figure 6.1).
Uniparentally reproducing organisms do not exhibit lateral gene exchange and
therefore cannot form gene flow communities. The term gene-flow community
must be distinguished from the term reproductive community (see reproductive
community). Gene-flow community is considered to be synonymous to species.
Gene transfer (or gene flow), lateral (or horizontal) Sexual gene transfer; the
transfer of genes via temporary or permanent fusion of two cells. This term
includes the fusion of sperm and egg as well as conjugation in ciliates or gene
transfer in bacteria or viruses.
Gene transfer (or gene flow), vertical (or genealogical) Gene transfer via
reproduction; the transfer of genes from the P generation to the F generations.
Genetic drift Disappearance or increase of allelic variants without conferring any
selective disadvantage or advantage. Mutation of neutral alleles is not recognized by
selection because it confers no disadvantage or advantage. Nevertheless, these alleles
can disappear in a population or be replaced by other alleles by chance alone.
Genotype The total set of genes of an organism (see phenotype).
Homeostatic property cluster A class of objects with traits that resemble each other.
In contrast to a natural kind (see natural kind), however, the traits do not need to be
present in each of the members of the class; they are not essential because they are not
necessary and sufficient for class membership. It is only necessary that the traits,
which lead to class membership, are sufficiently stable to be present in the members
of the class with a predictable probability. The term homeostatic property class is
similar to the term family resemblance.
Heterogametic and homogametic sex The heterogametic sex is the sex that
possesses an X/Y, X/0 or Z/W constitution. Therefore, the heterogametic sex
produces two different sorts of mature gametes during meiotic division: half are
X or Z gametes, and the other half are Y, 0 or W gametes. The homogametic sex is the
opposite: it produces only one type of mature gametes, X or Z gametes.
Homologous objects The descendants of replicating objects, having a recent
common ancestor. Composed structures, such as complex proteins or entire
organs or organisms, cannot be homologous because they are not replicating
objects and do not have a common ancestor. They are assembled from
components of different origins, and only some of their components can be
homologous. Furthermore, the concept of homology cannot be applied to objects
whose common ancestor traces far back in evolution. The term homology loses its
explanatory power when applied to these objects because all life on earth ultimately
has a common ancestor.