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Systematics • Branch of Biology that deals with classifying living things both current and prehistoric. 3 components: 1. Taxonomy: – Branch describing and naming new taxonomic groups (species) 2. Classification – Branch organizing information about organisms by arranging them into a hierarchical system 3. Phylogenetics – Branch determining the evolutionary history and relationships among the various forms of life through time Current Taxonomic Model Domain Kingdom Phylum / Division Class Order Family Genus Species Species The smallest group of organisms classified • Difficult to determine the criteria for what a species is. – Example: is a mule it’s own species? • A species is a population which can interbreed with each other (share a gene pool) to produce fertile offspring • This makes them a distinct biological unit • Part of the scientific name • e.g. scientific name of human : Homo sapien Scientific name of a cat: Felis domesticus Genus • Group of closely related species • All the species in a genus share common characteristics – Ex: a house cat, Felis domesticus, and a mountain lion, Felis concolor, share many similar characterisitcs, but are clearly different organisms Binomial Nomenclature • Naming system developed by Swedish botanist Carolus Linneaus • Each organism has a two part name • First the genus and then the species – Ex: Acer rubrum (red maple tree) Acer is the genus name rubrum is the species name • The species name is usually a Latin word describing a characteristic • Notice: genus name is capitalized, species name is not! Family • A family is a larger classification than genus and groups similar genera (plural for genus) together – Ex: all genera of cat-like animals are grouped in the family Felidae – Felis, Panthers, Acinonyx Order • The next largest classification (taxon) groups similar families together – Ex: Cats (family Felidae) and Dogs (family Canidae) are in the order Carnivora (carnivores) Class • Orders are grouped into classes, again based on common characteristics – Ex: all order of Carnivora are warm-blooded, have body hair and produce milk, so they are placed with the order Primates (incl. humans) in the class Mammalia Phylum (Division) • Classes are grouped into a phylum – Ex: mammals are placed in the phylum Chordata with birds, fish, and reptiles because they share a similar characteristic (of nervous system development) Cladogram Phylogenetic Tree Kingdom • Closely related Phyla are grouped into Kingdoms • There are six kingdoms: – Animalia, Plantae. Fungi, Protista, Eubacteria, Archaebacteria Domain • In 1990 a system of 3 Domains was introduced – Domain Eukaraya (includes Protists, Fungi, Plantae and Animalia Kingdoms) – Domain Bacteria (includes Kingdom Eubacteria) – Domain Archaea (includes Kingdom Archaebacteria) So where did this system come from? (the history) Aristotle (384 – 322 BCE) • Created the first widely used system of classification by dividing organisms into Animals and Plants Carolus Linnaeus (1707 – 1778) • Developed a hierarchical categorization system (kingdom, phylum, class, order, family, genus, species) • Grouped organisms based on their resemblance to other life forms • Developed the Binomial Nomenclature system (still in use today) 1850’s • Improvements in light microscope led to the discovery of a large number of organisms Ernst Haeckel (1866) • Proposed 3rd Kingdom Protista which includes all single celled organisms 1900’s • Invention of electron microscope and advancements in biochemistry • Discovery of Eukaryotic and Prokaryotic cells Robert Whitaker (1959) • Proposed 5 kingdom system (Plants, Animals, Fungi, Bacteria and Protists) Carl Woese (1970’s) • Analyzed base sequences of RNA in bacteria and protists and suggested that bacteria should be separated into two groups Eubacteria and Archaebacteria • Led to a Six Kingdom system in which Kingdom Bacteria (Monera) was separated into the Eubacteria and Archaebacteria kingdoms • 1990 Woese proposed a Three Domain scheme of clasification