Classification Chapter 18

What’s Wrong Here?

Classification To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner Taxonomy is the discipline of classifying organisms and assigning each organism a universally accepted name

What is the benefit of having a universal classification system?

Development of a Classification System Carolus Linnaeus- developed a two word naming system that is still in use today In Binomial Nomenclature each species is always assigned a two-part scientific name

The first part of the scientific name is the genus The first part of the scientific name is the genus. The first letter of this name is always capitalized--- Ursus The second part of the scientific name is the species, which is never capitalized ---- maritimus

Now You Try Examples: ursus maritimus homo sapiens canis familiaris

What’s in a Name When written together, the scientific name includes both the species and genus name of the organism This should be italicized when typed or underlined when written hand-written

Taxonomic Categories Linnaeus’s system of classification uses 7 taxonomic categories. Genus is a group of different species that share common characteristics Kingdom Phylum Class Order Family Genus Species

Taxonomic Characteristics Families are composed of different groups of genera (genus) that share similar characteristics Families are grouped into orders. Orders are grouped into classes. Classes are grouped into phyla (Phylum) Phyla (phylum) are grouped into a large category called a kingdom

Modern Evolutionary Classification Linnaeus compared structure and anatomy Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities Derived Characteristics are those that “show up” in newer parts of a lineage but are not in its older members

Modern Evolutionary Classification Cladograms are diagrams that show evolutionary relationships between groups of organisms

Modern Evolutionary Classification The genes of many organisms show important similarities at the molecular level. These similarities can be used as criteria to help determine classification All organisms use RNA and DNA to pass on information. All organisms use ATP as an energy-carrying molecule. Similarities in other important chemicals give us another way to compare them

Modern Evolutionary Classification Molecular clocks use DNA comparisons to estimate the length of time that two species have been evolving independently. This relies on the rate that neutral mutations accumulate in the DNA of different species

Kingdoms and Domains Using new tools available today, scientists have expanded upon Linnaeus’s system of classification. The 6 kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

Kingdoms and Domains Today, most scientists are now recognizing molecular evidence that requires the addition of a category even larger than kingdom: the domain Domains: Archaea Bacteria Eukarya