Classical Taxonomy& Molecular Phylogeny

[17.1-17.3]

SPI 5 Apply evidence from the fossil record, comparative anatomy, amino acid sequences, and DNA structure that support modern classification systems.SPI 6 Infer relatedness among different organisms using modern classification systems.

Classical Taxonomy

Taxonomy: identifying, naming, and classifying species based on natural relationships.

•Carl Linnaeus:– First formal system of taxonomic

organization– Organized into tiered groups

determined by shared characteristics and behaviors

• Species- individual species

• Genus- a group of species that share similar specific attributes

• Each step up shares increasingly broad general attributes

• Ex. American Black Bear– Eukarya, Animalia, Chordata,

Mammalia, Carnivora, Ursidae, Ursus, americanus

– U.americanus

• 3 Domains– Bacteria

– Archaea

– Eukarya

• 6 Kingdoms– Bacteria

– Archaea

– Protists

– Fungi

– Plantae

– Animalia

• Binomial nomenclature is where the organism is given a two part name– 1st part: genus name– 2nd part: specific/species name– Example:

• Full name: Escherichia coli• Abbreviated: E. coli

– Example:• Ursus americanus• U. americanus

• Scientists are moving away from classical taxonomy as the primary classification method for organisms.

• Why? What problems can you see as a result of classifying organisms on appearance and structure alone?

Molecular Phylogeny• Phylogeny is:

– the evolutionary history of a species– a classification of organisms according to the

order that they diverged from a common ancestor.

• It is based on genetic evidence of a pattern of ancestry and descent.

Species are grouped based on the relatedness of their genome

Cladograms• A cladogram is a branching diagram that

represents the proposed evolutionary history of a species. The group it represents is called a clade.

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The outgroup is the ancestral species that every other species on the cladogram is descended from / shares features with.

• The cladogram is constructed by ordering the members in the sequence that new traits appear.

• Each member shares its traits with every member that comes before it on the cladogram

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• Each branch represents divergence from a common ancestor as new traits appear in a population of the ancestor species

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Group Activity Instructions1. Examine the photos of the 16 species of anole

lizards.2. Sort the photos according to how they appear into as

many groups as you want. (i.e. color, legs, body shape, tail length, size, habitat, etc.)

3. Be prepared to explain your rationale for how you grouped the lizards.

4. Watch the short film – Lizards in an Evolutionary Tree

5. Revise your groupings if you wish.