1. Classification
Chapter 18

2. Taxonomy
Taxonomy—discipline in which scientists classify organisms and assign each organism a universally accepted name.
Biologists have identified and named about 1.5 million species so far.
Estimated between 2 and million species yet to be discovered.

3. Assigning Scientific Names
To eliminate confusion, scientists use Latin and Greek to assign scientific names.
In binomial nomenclature each species is assigned a two-part scientific name.
Scientific name is always written in italics.
First word is capitalized, and the second word is lowercased.
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4. Scientific Names
The first part of the scientific name is the genus to which the organism belongs.
Genus—group of closely related species.
The second part of a scientific name is unique to each species within the genus.
Ursus arctos and Ursus maritimus

5. Carolus Linnaeus
Linnaeus—Swedish botanist who developed bionomial nomenclature naming system and a hierarchical classification system.
Linnaeus’s classification system includes seven levels.
Taxon—each level in the naming system.
Seven levels are—species, genus, family, order, class, phylum and kingdom.

6. Taxon
Kingdom—largest and most inclusive of Linnaeus’s taxonomic categories.
Phylum—several different classes. Includes many different organisms that nevertheless share important characteristics.
Class—composed of similar orders.
Order—a broad taxonomic category composed of similar families.
Family—genera (plural of genus) that share many characteristics.
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7. Kingdoms Initially, Linnaeus named two kingdoms—Animalia and Plantae.
Currently, we have six different kingdoms.
Kingdoms—Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia
Domain—larger and more inclusive than a kingdom developed due to molecular analysis.

8. Domain—Bacteria and Archaea
Domain Bacteria—unicellular and prokaryotic with thick, rigid cell walls that surround a cell membrane
Contain kingdom Eubacteria
Domain Archaea—live in most extreme environment; volcanic hot springs, brine pools and black organic mud, cell walls lack peptidoglycan.
Contain kingdom Archaebacteria

9. Domain Eukarya Consists of all organisms that have a nucleus
Protista—eukaryotic organisms that cannot be classified as animals, plants, or fungi
Most protists are unicellular
Fungi—heterotrophs that feed on dead or decaying organic matter

10. Eukarya
Plantae—Multicellular organisms that are photosynthetic autotrophs.
Carry out photosynthesis and are nonmotile.
Contain cell walls that contain cellulose.
Animalia—Multicellular and heterotrophic.
Do not have cell walls and most can move for at least part of their life cycle.

11. Picture Credits