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CLASSIFICATION Ch Chapter 18 Living Environment Biologists use a classification system to name organisms, study diversity of life and group organisms in a logical manner. This is known as TAXONOMY. Why do we name everything using scientific names? • For example: homo sapiens For example: homo sapiens instead of human instead of human • So that biologists can be certain that everyone is discussing the same organism. q g y • Science requires both general and very specific categories to properly categorize all g g y organisms. In a good classification system, organisms placed in one group are more similar to each other than they are to y organisms of another group. Assigning Scientific Names • Latin and Greek names were assigned to all at a d G ee a es e e ass g ed to a organisms (because all biologists understood those languages). Organisms were originally named according to their description, but those d d h d b h could be quite long and inefficient. • During the 1800s, Carolus D i th 1800 C l Linnaeus, a Swedish Li S di h botanist proposed and developed the idea of binomial nomenclature. This is still the binomial nomenclature. This is still the classification system we use today. Each species is given a two‐part scientific name. Scientific Names • The The scientific name is always written in italics, scientific name is always written in italics, the first word is capitalized and the second word is lower case. The scientific name is made up of the genus and the species of an organism. For example: Ursus maritimus is the polar bear. Because there are many types h l b B h of bears, the genus name Ursus indicates that it is a bear and the species name maritimus it is a bear and the species name maritimus describes either where that particular species lives or names a characteristic of the species lives or names a characteristic of the species. What do you think maritimus means? • Mare Mare, Mar Mar • It refers to the ocean because polar bears usually live on pieces of ice that float in the usually live on pieces of ice that float in the ocean. Linnaeus’s System y Linnaeus’s system of classification uses seven taxonomic categories: kingdom, seven taxonomic categories: kingdom, phylum, class, order, family, genus, species. (King Phillip Came Over From Great Spain) (King Phillip Came Over From Great Spain • Due to Darwin’s theory of Evolution, scientists y , now categorize organisms based on the y y , j y evolutionaryy history they share, not just by similar traits. This process is called evolutionary classification. y • Cladistic analysis is the process of using a cladogram to map out evolutionary history, it to map out evolutionary history it uses derived characteristics to plot the course. Derived characteristics are characteristics that Derived characteristics are characteristics that appear in recent parts of a lineage but not in the older members the older members. • Finding the similarities in DNA and RNA has proven helpful in deciding whether certain organisms share a common ancestor or not. (Example: the case of the American vulture and the stork – both urinating on their legs to cool off – as opposed to the African vulture which does not follow this practice.) • As classification systems changed over time, the numbers of kingdoms changed too. There were originally only Plantae and Animalia, now there are Eubacteria, A h b t i P ti t F Archaebacteria, Protista, Fungi, Plantae i Pl t and Animalia. d A i li • Molecular analyses have given rise to a new category known as domains. The 3 domains are Bacteria (kingdom eubacteria), Archaea b t i ) A h (ki d (kingdom archaebacteria) and h b t i ) d Eukarya (kingdoms protista, fungi, plantae and animalia). Domain Bacteria Unicellular and prokaryotic U i ll l d k ti Have cell walls Range from free‐living organisms to deadly parasites S Some photosynthesize, some don’t h h i d ’ Some need oxygen, others are killed by it Contain peptidoglycen in cell wall Examples p of Domain Bacteria Kingdom: g Eubacteria Examples: • Streptococcus • Escherichia coli Domain Archaea Unicellular and prokaryotic Live in extreme environments like: volcanoes, black organic mud devoid of oxygen No peptidoglycen in cell wall Examples p of Domain Archaea Kingdom: g Archaebacteria Examples: • Methanogens – produce methane as a b byproduct d off anoxic i conditions di i lik like wetlands l d or human intestines (methane in flatulence) • Halophiles – salt-loving…they die without a lot of salt Domain Eukarya y All organisms in domain Eukarya have a nucleus Protista • can be photosynthetic or hetertrophic • can be unicellular or multicellular • may share characteristics of plants Examples: amoeba, paramecium, slime molds giant kelp molds, Domain Eukarya y continued Fungi • heterotrophs • multicellular ((except p yyeast)) Examples: mushroom, yeast Domain Eukarya y continued Plantae • multicellular • photosynthetic h h i autotrophs h • nonmotile • cell walls contain cellulose Examples: cone cone-bearing bearing, flowering-plants flowering plants, ferns ferns, mosses Domain Eukarya y continued Animalia • multicellular • heterotrophic h hi • no cell walls • Motile Examples: sponges, sponges worms worms, insects insects, fishes fishes, mammals Molecular Clocks • Molecular Clocks:
