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Definition
| An evolutionary process in which one species splits into two or more species. |
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Definition
| Evolutionary change below the species level; change in the allele frequencies in population over generations. |
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Term
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Definition
| evolutionary change above the species level, including the origin of a new group of organisms or a shift in the broad pattern of evolutionary change over a long period of time. Examples of macroevolutionary change include the appearance of major new features of organisms and the impact of mass extinctions on he diversity of life and its subsequent recover. |
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Term
| Biological Species Concept |
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Definition
| Definition of a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups. |
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Definition
| The existence of biological factors (barriers) that impede members of two species from producing viable fertile offspring. |
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Definition
| Offspring that results from the mating of individuals from two different species or two true-breeding varieties of the same species. |
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Definition
| A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted. |
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Definition
| A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults. |
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| Morphological Species Concept |
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Definition
| A definition of species in terms of measurable anatomical criteria. |
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Term
| Ecological Species Concept |
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Definition
| A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment. |
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| Phylogentic Species Concept |
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Definition
| A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life. |
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Definition
| The formation of new species in populations that are geographically isolated from one another. |
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Definition
| The formation of new species in populations that live in the same geographic area. |
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Definition
| A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division. |
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Definition
| An individual that has more than two chromosome sets that are all derived from a single species. |
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Term
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Definition
| A fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combing their chromosomes. |
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Definition
| A geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry. |
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Definition
| A process in which natural selection strengthens prezygotic barriers to reproduction, thus reducing the chances of hybrid formation. such a process is likely to occur only in hybrid offspring are less fit than members of the parent species. |
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Term
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Definition
| In the fossil record, long periods of apparent stasis, in which a species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change. |
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