2 - BIO 94 NOTES (1/7/09) tree of life o the cell theory...

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BIO 94 NOTES (1/7/09) tree of life o the cell theory and the theory of evolution by natural selection imply that all species come from preexisting species and that all species, past and present, trace their ancestry back to a single common ancestor o speciation – divergence process in which natural selection has caused populations of one species to diverge to form new species (change over time) o tree of life – family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base taxonomy – the effort to name and classify organisms o Linnaeus’ taxonomic system for classifying organisms, each organism is given a unique two-part scientific name consisting of the genus and the species A genus is made up of a closely related group of species (inter- mate and have offspring) A species is made up of individuals that regularly breed together or have characteristics that are distances from those of other species o Taxonomic levels Linnaeus’ system is hierarchical with nested taxa . The taxonomic levels from least to most specific are as follows: kingdom (animalia) phylum (chordate) class (mammalian) order (primates) family (hominidae) genus (homo) species (homosapiens) origin of the phylogenic tree of life o Carl Woese and colleagues studied small subunit rRNA, as a means fro understanding the evolutionary relationships among organism rRNA sequences should be very similar in closely related organisms but less similar in organism that are less closely related phylogenic tree reflects these relationships among species. Branches that are closely to one another represent species that are
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2 - BIO 94 NOTES (1/7/09) tree of life o the cell theory...

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