Transcript Classification: What`s in a Name

Classification and Beyond
Chapters 19
Why do we name things?
• To distinguish one thing from another
• To communicate with others more
effectively
• It forces us to examine things more closely
and make distinctions
Classical Taxonomy – the Binomial
System
• Carl von Linné (a.k.a.) Carolus Linnaeus
• Binomial nomenclature – each organism
gets two names, a genus name and a
species name. These are always used
together. You cannot use a species name
without the genus name.
If you ordered americanus in a
restaurant ….
• Homarus americanus – lobster
• Ursus americanus – black bear
• Bufo americanus – American toad
3 Domains
• Archaea
• Eubacteria
• Eukarya
• Kings Play Chess On Fine Grained Sand:
Kingdom
Phylum
Class
Order
Family
Genus
Species
Taxon - a group of organisms at any particular
level in this system
Biological Species Concept
• Biological species are groups of actually or
potentially interbreeding populations that
are reproductively isolated from other such
groups.
• Reproductive unit
• Genetic unit
• Ecological unit
Phenetics
• Based on observable characteristics
• Uses “yes or no” questions
• “numerical taxonomists”
– Choice of characteristics is subjective
– Groupings unrelated to evolution
– Environment affects some characteristics
more than others
Cladistics
• Produce evolutionary trees
• Groupings include the ancestral species
and all its descendants – Monophyletic
• Uses physical characteristics, fossil record
and sequences of proteins and genes
• Sometimes it agrees with classical
taxonomy and sometimes it does not
DNA and protein sequencing
• Evolve the same way as other
characteristics – homologous or
analogous?
• Also involves subjective choices
• Noncoding DNA tends to change at a
more constant rate – can be used as a
“molecular clock.”