Classification of Organisms

BiologyChapter 17

Classifying Organisms

• Taxonomy: the science of describing, naming, and classifying organisms– Taxon: a group within a taxonomic system

• Aristotle: classified organisms into two groups– Plants and animals• Why isn’t this useful?

Carolus Linnaeus

• Devised system of grouping organisms into hierarchical categories – Using form and structure

• Domain• Kingdom• Phylum• Class• Order• Family • Genus• species

Binomial Nomenclature

• Two part naming system (scientific name)– Use genus and species name– Written in italics with genus name capitalized– In Latin because it is an unspoken language, so it

never changes– Example• Humans: Homo sapiens

Systematics

• Phylogeny: the evolutionary history of a species– Phylogenetic Diagram (phylogenetic tree)• Looks like a family tree and has branching pattern that

indicates how closely related subset taxa are thought to be

Cladistics

• Cladistics– A system the uses shared characteristics and

derived characters as the only criteria for grouping• Shared character: a feature that all members

in the group have in common• Derived character: a feature that evolved only

within the group under consideration

Cladistics

• Clad: used to describe a group of organisms that includes an ancestor and all of its descendants

• Cladogram: Diagram• Molecular Cladistics: looks at derived amino

acids at each position in a protein

Three Domains of Life

• Domain Bacteria– Prokaryotic – Single-celled– Have a cell wall– Heterotrophic and autotrophic– Ex: bacteria

Three Domains of Life

• Domain Archaea– Prokaryotic– Most live in harsh environments– Have cell walls– Unicellular– Heterotrophic and autotrophic

Three Domains of Life

• Domain Eukarya– Have eukaryotic cells– Includes kingdoms plants, animals, fungi, and

protists

Domain Eukarya

• Kingdom Protista– Eukaryotic– Not plants, animals or fungi– Most are unicellular– Some multicellular but lack tissue organization– Autotrophic or heterotrophic

Domain Eukarya

• Kingdom Fungi– Eukaryotic– Heterotrophic– Unicellular and multicellular– Absorb their food through extracellular digestion

Domain Eukarya

• Kingdom Plantae– Eukaryotic– Muclticellular– Most are autorophic

Domain Eukarya

• Kingdom Animalia– Eukaryotic– Multicellular– Heterotrophic– Develop from embryos