TAXONOMY Biology Corsicana High School

Taxonomy the science of classification of living things classification---putting things into groups

Development of Classification Systems

Aristotle ancient Greek philosopher. Devised a simple classification plan for organisms: Plants---divided into 3 groups on the basis of stem structure –herbs---small, soft, flexible stems –shrubs---several woody stems –trees---one main woody stem Animals---divided into 3 groups on the basis of habitat –land dwellers, water dwellers, air dwellers

Carolus Linnaeus 18th century Swedish botanist devised a classification system for organisms based on structural similarity much of his system is still in use today

Linnaeus’ Classification System had seven major taxonomic groups: –kingdom –phylum (pl. = phyla) [in Plant Kingdom: Division] –class –order –family –genus (pl. = genera) –species (pl. = species)

Species one particular type of organism members of a species are similar in structure, have a particular number of chromosomes, and can mate and produce fertile offspring

Varieties groups of slightly different organisms in the same species examples: breeds of dogs, cats, cattle, etc. are all members of the same species

Modern Taxonomy is Based on: structural similarity---alike in structure biochemical similarity---molecules are similar (ex: proteins) genetic similarity---DNA shows evolutionary relationships

Phylogeny the evolutionary history of a species phylogenetic tree---a visual model of the inferred evolutionary relationships between species dichotomous key---a written set of choices that leads to the name of an organism

Classification Systems are artificial devices for studying organisms are subject to change as new information about organisms becomes available

Scientific Names

Common Names everyday names used for organisms may be confusing because: –they are different in different places (example: cougar, mountain lion, and panther are all common names for the same organism) –may not describe the organism accurately (example: silverfish and jellyfish are not fish) –the same common name may be used for more than one type of organism (example: there are several species of maple trees)

Linnaeus Chose Latin Because: Latin was no longer in use; therefore, the meanings of the words would not change Scientists all over the world know Latin The Latin language is a descriptive language, and is the root of many modern languages

Binomial Nomenclature two-word naming The first word of a scientific name is the genus name –a Latin noun –Capitalized and underlined or italicized The second word is the species name –a Latin adjective, describing the noun –not capitalized, but is underlined or italicized

Homo sapiens the scientific name for humans Homo = man sapiens = thinking Textbooks and other publishers may write scientific names in italics instead of underlining them example: Homo sapiens

Complete Classification of Humans Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: sapiens

Six-Kingdom Classification System

Kingdom Eubacteria and Archaebacteria unicellular, prokaryotic examples: bacteria, blue-green bacteria (a modern, six-kingdom system splits this kingdom into two separate kingdoms: –Archaebacteria (“ancient bacteria”)no peptidoglycan in their cell walls –Eubacteria (“true bacteria”)does contain peptidoglycan in their cell walls

Kingdom Protista eukaryotic, unicellular or multicellular examples: protozoans, algae, water molds, slime molds

Kingdom Fungi eukaryotic with a continuous filamentous body with many nuclei heterotrophic---obtain food by absorption examples: yeasts, mold, mildew, mushrooms

Kingdom Plantae multicellular, eukaryotic autotrophic--green plants examples: mosses, ferns, seed plants

Kingdom Animalia multicellular, eukaryotic heterotrophic---obtain food by ingestion (eating) examples: sponges, jellyfish, worms, insects, vertebrates