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the major changes in the history of life


formation of new species

Biological Species Concept

a species concept defining a species as a population or group thereof whose members potentially interbreed and with one another in nature to produce


group of similar organisms that can breed and produce fertile offspring

Prezygotic Barriers

these prevent mating or fertilization between species

Postzygotic Barriers

mechanisms that operate should interspecies mating actually occurs and form hybrid zygotes

Allopatric Speciation

the initial block to gene flow is a geographic barrier that physically isolates the splinter population

Sympatric Speciation

the orgin of new species without geographic isolation

Punctuated Equilibrium

this addresses the nongradual appearance of species


a structure that evolves in one context and later becomes adapted for other functions


the retention into adulthood of features that were solely juvenile in its ancestors

Geologic Time Scale

this reflects a consistent sequence of geolic periods

Radiometric Dating

based on the decay of radioactive isotopes


the study of diversity and relationships or organisms, both past and present


the identification, naming and classification of species


consisting of two names or terms


this is the first part of the binomial that which the species belong


this places similar genera in the same family, puts families in orders, orders into classes, classes into phyla, phyla into kingdoms and kingdoms into domains


the evolutionary history of a species

Phylogenetic Tree

the principle of common descent is reflected in the branches of the tree

Convergent Evolution

species from different evolutionary branches may have certain structures that are superficially similar if natural selection has shaped analogous adaptations


the scientific search for clades


consists of an ancestral species and all its descendants a distinctive branch in the tree of life

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