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Classification. Ch 18.1 and 18.3. Why Classify?. Organization We have IDed over 1.7 millions species What group has the most diversity? Systematics - the science of naming and grouping organisms Goal is to organize living things into groups (taxa) that have biological meaning.
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Classification Ch 18.1 and 18.3
Why Classify? • Organization • We have IDed over 1.7 millions species • What group has the most diversity? • Systematics- the science of naming and grouping organisms • Goal is to organize living things into groups (taxa) that have biological meaning
Why Classify? • Communication • Use a standard language- not common names but scientific ones = less confusing • Based on Latin and Greek • Developed by Linnaeus • Binomial Nomenclature- each species has a 2- part name • First part = Genus (capitalize 1st letter) • Second part = species (don’t capitalize first letter) • ALWAYS underlinded or in italics • Ex. Homo sapiens
Linnaean Classification System • Originally 4 ranks but has expanded into 7 • Kingdom • Phylum • Class • Order • Family • Genus • Species • How do you remember this? • Kings Play Chess On Fine Gold Squares • As you move down the classification: • Characteristics become more specific • Number of organisms in each level decreases
Another way to think about it • Kingdom- continent • Phyla- country • Class- state • Order- city • Family- street • Genus- house number • Species- specific person
For Humans • Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Primates • Family: Hominidae • Genus: Homo • Species: Sapiens
What is this classification based on? • Traditionally • Groups with visible similarities • Linnaeus was before Darwin so classification based largely on physical characteristics • Today • Also looking for evolutionary relationships • DNA- shared genes- makes trees more accurate
Identification of Organisms • Use of a Dichotomous Key • Series of paired statement or questions with alternative characteristics • Each step leads to a smaller subset • Goal: Identify unknown organisms
Intermission • Dichotomous Key Time!!
The Kingdoms • The way we classify has changed over time- today 6 kingdoms • From 5 6 • Monera = bacteria • By the ‘90s realized that there were 2 distinct kinds
The Domains • 2 Prokaryotic groups even more different than originally thought • Domains- larger more inclusive category than Kingdom • 3 domains • Bacteria (Kingdom: Bacteria) • Archea (Kingdom: Archaebacteria) • Eukarya (Kingdom: Animalia, Plantae, Fungi, Protista)