Unit 6: Classification and Diversity KEY CONCEPT Organisms can be classified based on physical similarities. Taxonomy is the science of naming and classifying organisms. TAXONOMY – CLASSIFICATION A taxon is a group of organisms in a classification system. For example: Domain, Kingdom, Phylum, Order, Class, Family, Genus, Species are taxons.

Unit 6: Classification and Diversity Linnaeus was the first one to classify living things. Linnaeus classification system has seven levels OR taxons. Each level is included in the level above it. Levels get increasingly specific from kingdom to species.

Unit 6: Classification and Diversity Why name things?

Unit 6: Classification and Diversity

Scientific names help scientists to communicate. –Some species have very similar common names. –Some species have many common names.

Unit 6: Classification and Diversity Linnaeus developed the scientific naming system still used today. Binomial nomenclature is a two-part scientific naming system. –E.g.: Homo sapiens (Homo=genus, sapiens=species) –uses Latin words –scientific names always written in italics in print, or underlined in text. –two parts: genus and species

Unit 6: Classification and Diversity A genus includes one or more physically similar species. –Species in the same genus are thought to be closely related. –Genus name is always capitalized. A species descriptor is the second part of a scientific name. –always lowercase –always follows genus name; never written alone Tyto alba

Unit 6: Classification and Diversity The Linnaean classification system has limitations. Linnaeus taxonomy doesn’t account for molecular evidence. –The technology didn’t exist during Linneaus’ time. –Linnaean system based only on physical similarities.

Unit 6: Classification and Diversity Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships.

Unit 6: Classification and Diversity KEY CONCEPT Modern classification is based on evolutionary relationships.

Unit 6: Classification and Diversity Cladistics is classification based on common ancestry. Phylogeny is the evolutionary history for a group of species. –evidence from living species, fossil record, and molecular data –shown with branching tree diagrams

Unit 6: Classification and Diversity Cladistics is a common method to make evolutionary trees. –classification based on common ancestry –species placed in order that they descended from common ancestor

Unit 6: Classification and Diversity A cladogram is an evolutionary tree made using cladistics. –A clade is a group of species that shares a common ancestor. –Each species in a clade shares some traits with the ancestor. –Each species in a clade has traits that have changed.

Unit 6: Classification and Diversity Derived characters are traits shared in different degrees by clade members. –basis of arranging species in cladogram –more closely related species share more derived characters –represented on cladogram as hash marks FOUR LIMBS WITH DIGITS Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE DERIVED CHARACTER

Unit 6: Classification and Diversity FOUR LIMBS WITH DIGITS Nodes represent the most recent common ancestor of a clade. Clades can be identified by snipping a branch under a node. Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW FEATHERS AND TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE NODE DERIVED CHARACTER CLADE

Unit 6: Classification and Diversity Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. Molecular evidence reveals species’ relatedness. DNA is usually given the last word by scientists.