Speciation and Macroevolution Flashcards
Biological species concept
A species consists of one or more populations whose members interbreed in nature to produce fertile offspring and do not interbreed with members of different species. However, it only applies to sexually reproducing organisms. And some species may occasionally successfully interbreed.
Prezygotic barriers
They are reproductive isolating mechanisms that prevent fertilization from taking place. Temporal isolation occurs when two species reproduce at different times of the day, season or year. Habitat isolation when two closely related species live and breed in different habitats in the same geographic area. Behavioral isolation distinctive behaviors prevent mating. Mechanical isolation is due to incompatible structural differences in the reproductive organs. Gametic isolation, gametes from different species are incompatible because of molecular and chemical differences.
Postzygotic barriers
They are reproductive isolating mechanisms that prevent gene flow after fertilization has taken place. Hybrid inviability is the death of interspecific embryos during development. Hybrid sterility as it sounds. And Hybrid breakdown prevents the offspring of hybrids from succesfully reproduce.
Speciation
It is the evolution of a new species from an ancestral population.
Allopatric speciation
It occurs when one population becomes geographically isolated from the rest of the species and subsequently diverges.
Sympratric speciation
It does not require geographic isolation. In plants it can occur when a polyploid individual is an allopolyploid hybrid derived from two species.
Punctuated equilibrium
Short periods of active speciation are interspersed with long periods of stasis.
Phyletic gradualism
Populations slowly diverge from one another by the accumulation of adaptive characteristics within a population.
Macroevolution
It concerns large-scale phenotypic changes in populations that typically warrant the placement of the populations in taxonomic groups at the species level and higher, that is, new species, genera, families, orders, classes, and even phyla, kingdoms, and domains.
Evolutionary novelties may be caused by
Changes during development. Changes in regulatory genes.
Preadaptations: structures that originally fulfilled one role but changed in a way that was adaptive for a different role.
Allometric growth
Varied rates of growth for different parts of the body.
Paedomorphosis
The retention of juvenile characteristics in the adult, occurs because of changes in the timing of development.
Adaptive radiation
It is the process of diversification of an ancestral species into many new species. Adaptive zone are new ecological opportunities that were not exploited by an ancestral organism.
Extinction
It is the death of a species. Background extinction is the continuous, low-level extinction of species. Mass extinction is the extinction of numerous species and higher taxonomic groups.
