Biology 3466B Lecture Notes - Lecture 9: Crataegus, Species Complex, Zygote
25 Aug 2013
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Document Summary
When examining different species of the globe, each should: Reflect morphological distinctiveness (have different or unique phenotypic qualities). Reflect evolutionary independence (be able to survive successfully). Be testable (in the field of its natural setting). Be applicable to sexual and asexual forms, cryptic species (morphologically similar), fossils, etc. It is quite difficult to accurately define the parameters for a species, but three concepts exist to alleviate this difficulty: Morphological species concept (msc): groups of populations with distinct morphological differences; incredibly identifiable in the field. Biological species concept (bsc): groups of potentially or actively interbreeding natural populations which are reproductively isolated from other groups. Phylogenetic species concept (psc): the smallest group whose members descend from a common ancestor and who possess defining (derived) characteristics that distinguish them from other groups; shows the evolutionary relationships among different species. Isolating barrier: geographic/allopatric (different place) or reproductive/sympatric (same place). Divergence: mutation, genetic drift or selection; describes the evolutionary portion of separation.
