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CLASSIFICATION & BIODIVERSITY Why Classify ? •The world is populated by at least 10 million different organisms. •To ensure accurate communication about organisms, biologists use • Taxonomy is the branch of biology that names and groups organisms according to their characteristics and Early Classification Systems •Aristotle (over 2000 yrs ago) devised the first classification system. •grouped plants by size (small, med, large) •grouped animals by habitat – land, water, air dwellers •This was not a great system but it persisted until Linnaeus (Swedish botanist) came up with another one in the mid-1700’s Linnaeus’ System Linnaeus’s system relied upon hierarchical categories using mainly the organism’s morphology (). Kingdoms expanded... •As biologists learned more about the natural world, they realized that two kingdoms did not adequately represent all the diversity of life. Levels of Classification Scientists classify organisms into seven basic levels in the hierarchy (expanded since Linnaeus): kingdom, phylum, class, order, family, genus, and species. - Kingdom is the largest category - Species, the smallest grouping. The placement of species is meant to indicate. Why group organisms at all? •Make sense of life on Earth •Predict characteristics shared by members of a group •Show (since Darwin’s time) Why Binomial Nomenclature? •There is confusion about common names: •Ex. This cat’s common name: •mountain lion; puma; cougar; panther; jaguar •These two birds are both called “robins” To avoid this confusion scientists assign each species a unique. Biological Naming of Species • Binomial nomenclature is a system developed by Linnaeus that consists of two-part names for each organism. • The scientific name consists of the genus and species. It is italicized when typed or underlined when handwritten. (“species” is sing/plural -- “genera” is plural for “genus”) •Genus - Capitalized; species - not capitalized •standard throughout the world (unlike common name) •in Latin (or Greek) - the scientific language of the day •unique to the organism •Naming rights of new species go to lead scientist on the team (i.e. Dracorex hogwartsia) What is the scientific name of these two organisms? Bobcat: Lion: Kingdom Phylum Class Let’s try humans... Order Family Genus Species Binomial Kingdom Now find another organism from the plant kingdom Phylum Class Order Family Genus Species Problems with Classification •Because of convergent evolution, analogous characters sometimes make it seem like unrelated organisms are related •Ex. These vultures and plants are unrelated and from different continents. •To solve this problem, taxonomists now make use of etc. •Taxonomists have developed a way to build family trees (called cladograms) which show the evolutionary relationship between species. •These are made by finding shared derived characteristics between species. () •These characteristics are placed on the cladogram where they first developed – all organisms that evolved after that point have the characteristic. Cladistics Kingdoms vs. Domains • As biologists learned even more about the natural world, they realized the bulk of life on Earth were bacteria. • • • Bacteria: common simple single cells: (prokaryotes) Eubacteria: simple single cells living in harsh environments (prokaryotes) Eukaryotes: includes some single celled (but more complex organisms) and ALL multicellular life Three Domain System •More recently, comparing sequences of ribosomal RNA in different organisms has helped scientists determine that living organisms seem to fall into three broad groups or domains.