Facts Of Evolution: Speciation And Extinction

Facts Of Evolution (Part 4): Speciation And Extinction. --- Please subscribe to Science & Reason: • • • --- EVOLUTION: 1. Does The Evidence Support Evolution? 2. Vitamin C And Common Ancestry More..F2N2l... 3. Are We Descended From Viruses? 4. Does The Fossil Record Support Evolution? 5. Where Are The Transitional Forms? --- SPECIATION is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages. Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are geographically isolated from one another: allopatric, peripatric, parapatric, and sympatric. Speciation may also be induced artificially, through animal husbandry or laboratory experiments. Observed examples of each kind of speciation are provided throughout. • --- In biology and ecology, EXTINCTION is the end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "re-appears" (typically in...

Channel: LiveLeak Video Length: 0s Date Found: Wed, Jul 28 2010 12:33 AM Category: Educational Date Produced: Tue, Mar 02 2010 12:00 AM View Count: 0