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Cladistics - is a relatively new system of phylogenetics classification that uses shared derived characters to establish evolutionary relationships. A derived character is a feature that apparently evolved only within the group under consideration. There are three basic assumptions in cladistics: 1.Organisms within a group are descended from a common ancestor. 2.There is a bifurcating pattern of cladogenesis. 3.Change in characteristics occurs in lineages over time. A phylogenetic tree based on a cladistic analysis is called a cladogram. What derived character is shared by all the animals on the cladogram on the next slide? The Dichotomous Key • A key is a device for easily and quickly identifying an unknown organism. • The dichotomous key is the most widely used type in biological sciences. • The user is presented with a sequence of choices between two statements, couplets, based on characteristics of the organism. By always making the correct choice, the name of the organism will be revealed. A. one pair of wings 1. B. Two pairs of wings • Domain Archaea – Includes newly discovered cell types The Three Domains – Contains 1 kingdom – the Archaebacteria •Domain Bacteria – Includes other members of old kingdom Monera – Has 1 kingdom – the Eubacteria •Domain Eukarya – Includes all kingdoms composed of organisms made up of eukaryotic cells – Protista – Fungi – Animalia – Plantae The major classification levels, from most general to most specific (several of these have subdivisions) A group at any level is a taxon. Categories within Kingdoms Kingdoms are divided into groups called phyla Phyla are subdivided into classes Classes are subdivided into orders Orders are subdivided into families Families are divided into genera Genera contain closely related species Species is unique