bio 117 lecture7
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- Phylogentic species concept
- species are the smallest monophyletic units in a phylogenetic tree
- Linnaean scheme of taxonomy
- classified relationships based on similarity of apperarace
- classical process of taxonomy
- use of taxonomic characters to describe taxonomic units
- Process of defining the phylogenetic species
- a) reconstruct evolutionary history of a group using genetic criteria, b) determine monophyletic goup, each made up of ancestral population characterized by common DNA sequences, c) identify the smallest monophyletic group with just a cluster of different poplations like organisms (problem; one or very few alleles separate two different populations
- some important rules to taxonomy
- a) bionomal species names, b) hierarchial names, c) type specimen
- Temporal problems (in geological time)
- species lineage gradually changes over time, with no overlap in taxonomic characters, at what point do you consider the starting point for characterizing a particular species???
- spatial problems (on a geographic scale)
- species identification in geographic contact zones that show interbreeding, (a single species may show interbreeding between two adjacent subpopulations but not between individuals at two ends of the gradient 'circle species' EX. pacific coast salamanders)
- Darwinian scheme of taxonomy
- a lineage based system with all organisms being derived from a commmon universal prototype
- initial definitions for species concepts
- a] speciation- emergence of new species from pre-existing species, b] species- an evolutionarily independent population or group of populations
- classical taxonomy
- the science in naming and classifying organsims (quest to understand biodiversity through classification)
- morphological species concept
- species must have different structural taxonomic characteristics (problem; some species look the same but dont interbreed in nature)
- what are criteria of good taxonomic characters
- a) interspecific character community, b) intraspecific character consistency, c) characters resistant to environmental change
- biological species concept
- species must be reproductively isolated or do not mate with each other, or because matings do not result in fertile offspring (problem; some species can breed in the lab but dont have the opportunity to breed in nature, is this a fair test?)
- other difficulties in identifying a seprate species
- spatial problems (geographic scale) and temporal problems( geological time)
- modern definition of taxonomy
- naming and placement of each type of organism in a hierachy showing phylogenetic relationshis and giving each organism a unique name