Classification of Living Things TEK 8A: Define taxonomy and recognize the importance of a standardized taxonomic system to the scientific community. TEK 8B: Categorize organisms using a hierarchical classification system based on similarities and differences shared among groups. TEK 8C: Compare characteristics of taxonomic groups, including archaea, bacteria, protists, fungi, plants and animals.

Finding Order in Diversity Tacitus bellus Finding Order in Diversity Biologists use a classification system to name organisms and group them in a logical manner. Taxonomy is the branch of biology that groups and names organisms based on their common characteristics. All scientists throughout the world will be using the same name! Classification systems change with expanding knowledge. Populus tremuloides Quaking Aspen Benefits of Taxonomy All scientists are using the same name. Organisms are organized based on common characteristics. A standardized name clarifies discrepancies when different common names are used around the world.

Taxons and Binomial Nomenclature Linnaeus’s hierarchical system of classification includes eight levels (from largest to smallest) Ex. Grizzly Bear (common name) Domain Eukarya Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Ursidae Genus Ursus Species arctos Binomial nomenclature uses the two most specific levels of classification as the scientific name: (unique name) Genus species Each organism is referred to by it’s two-part name: Ex. Grizzly bear is: Ursus arctos Ursus arctos (scientific name) In 1735, Carolus Linnaeus published the first edition of his Systema Naturae, which set forth his system for classifying all living things.  It has since been continually revised and expanded. Each of the levels is called a TAXON

System of Classification DK P C O F G S System of Classification The most closely-related organisms will be in the same species The more specific you go down the classification system, the more characteristics the organisms will have in common. ** If two organisms belong to the same Family, they also belong to the same Order, Phylum, Kingdom and Domain! **Two organisms cannot be the same species if they are not the same in all other classifications! Taxonomic categories, an acronym: Domain Dear Kingdom King Phylum Phillip Class Came Order Over Family For Genus Good Species Soup Domain Kingdom Phylum Class Order Family Genus Species Hierarchical Classification Carolus von Linnaeus created a hierarchical classification system using seven taxonomic categories, or taxa (Kingdom, Phylum, Class, Order, Family, Genus, Species). These categories are based on shared physical characteristics, or phenotypes, within each group. Beginning with kingdom, each successive level of classification becomes more and more specific. Organisms within the same order have more in common with one another than organisms within the same class. For example, all species of bears are mammals, but not all mammals are bears. A useful pneumonic tool to help students remember the hierarchical classification system is: “King Phillip Came Over For Green Soup,” with the first letter of each word representing each category, beginning with kingdom and ending with species. References: Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Ed. Benjamin Cummings.

Domains: Most inclusive (broadest) category There are 3: Eukarya – includes Kingdoms: Protista, Fungi, Plants & Animals Bacteria – Kingdom Eubacteria Archaea – Kingdom Archaebacteria Organisms are placed into Kingdom categories by: Cell type Nutrient acquisition Reproduction

Cladogram Taxonomic Diagrams Which organism is the outgroup Hagfish Which 2 organism are more closely related Attempt to trace the process of evolution by focusing on shared features Mouse and Chimp

Dichotomous Keys Identify Organisms Dichotomous keys contain pairs of contrasting descriptions. After each description, the key directs the user to another pair of descriptions or identifies the organism. Example: 1. a) Is the leaf simple? Go to 2 b) Is the leaf compound? Go to 3 2. a) Are margins of the leaf jagged? Go to 4 b) Are margins of the leaf smooth? Go to 5 Dichotomous Keys of Identify Organisms Identification is the process of finding the named group to which an organism belongs. Dichotomous keys are useful tools to help identify different organisms and usually are found in field guides. Identification in the field is based on features that are observable to the eye; therefore, it is important to remember that a key is an identification tool and is not synonymous with phylogenetic diagrams, which communicate hypothesized evolutionary history. Dichotomous keys are constructed of contrasting pairs of statements. To use a dichotomous key, begin with the first pair of statements and follow the directions at the end of each statement until you reach the name of the organism you are trying to identify. With each new organism, always start at the beginning of the key (1a and 1b). The ability to use dichotomous keys is an important skill and should be incorporated into instruction throughout the year. It is important to note that when constructing a dichotomous key, each pair of contrasting descriptions must deal with the same characteristic. For example the margin of the leaf might be used for the first pair of descriptors, and the shape of the leaf might be used for another pair. An incorrect pair of statements might be: 1a) Is the leaf heart shaped? 1b) Are the edges lobed? References: Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Ed. Benjamin Cummings.

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