Transcript Chapter 18
Chapter 18 Classification Of Living Things Finding Order in Diversity • There are millions of different species on Earth. To study this great diversity of organisms, scientists must give each organism a name & organize them into groups in meaningful ways. • Taxonomy is the discipline of naming and classify organisms. • Taxonomic names are universally accepted. Common names for organisms vary by regions (i.e. cat vs. gato), so a worldwide acceptance of a single species name had to occur. • A good classification system groups together organisms that are similar to each other than they are to other organisms. Carolus Linnaeus • Scientist in the 1700s who developed binomial nomenclature. • Binomial nomenclature is a two-word naming system that assigns every living species a two-part name. • Ex. Ursus maritimus is the species name for the polar bear. Homo sapiens is the species name for humans. • The first part of the name refers to the genus that a species belongs to and the genus plus the second part of the name refers to the species name. • Ex. All bears belong to the genus Ursus, but only the polar bear’s species name is Ursus maritimus. • Add to notes- First name is always capitalized and the second name is always lower case; if not italic the name must be underlined. • There are 7 different levels (taxons) to Linnaeus’ classification system: Kingdom Broadest Phylum Class Order Family Genus Species Most specific • Originally, Linnaeus named two kingdoms (Plantae and Animalia) of all living things, but later scientists added more. Modern Evolutionary Classification • Early classification systems were based only on visible similarities. • Biologists now group living things according to evolutionary relationships. • Many biologists now use a method called cladistic analysis, which is based on derived characteristics. Derived characters are new traits that arise as a group evolves over time, so they are found in closely related species, but not in their distant ancestors. • Derived characters can be used to construct a cladogram, which is a diagram that shows the evolutionary relationships among a group of organisms kind of like a family tree. Kingdoms and Domains • As biologists learned more about the natural world, they learned that Linnaeus’ two kingdoms, Animalia and Plantae, did NOT accurately represent all living things on Earth. • Microorganisms, like bacteria, were discovered and placed into two kingdoms called Archeabacteria and Eubacteria. Protists were seperated and placed into kingdom Protista and mushrooms, yeaast and molds were placed into the kingdom Fungi. 5- Kingdom System of Classification • By the 1990s, a six-kingdom system of classification was proposed. From the most simple to the most complex they are: Eubacteria SIMPLE Archaebacteria Protista Fungi Plantae Animalia COMPLEX • Recently, scientists have added a new taxon called the domain, which exists above the kingdom level of classification. • The three domains are: Bacteria, Archae and Eukarya. • The domain Bacteria contains single-celled, prokaryotic organisms whose cell walls DO contain a substance called peptidoglycan. • The domain Archae contains single-celled, prokaryotic organisms whose cell walls do NOT contain the substance peptidoglycan. • The domain Eukarya contains all organisms that are Eukaryotic (have nuclei). » gram “+” stain appear purple or brown; thick cell wall » gram “-” stain appear pink or red; thin cell wall or no wall Bacteria Domains Eukarya Archae Archaebacteria Kingdoms Eubacteria Protista, Fungi, Plantae & Animalia Remember the 8 taxonomic levels of classification Kingdom Did King Phillip Cut Onions For Good Soup? Characteristics Unicellular, prokaryotic bacteria, whose cell walls contain peptidoglycan; known to cause disease; fall under Domain Bacteria Archaebacteria Protista Unicellular, prokaryotic bacteria that live in harsh conditions; cell walls DO NOT contain peptidoglycan; fall under domain Archae Very diverse group of mostly microscopic, aquatic organisms; in Domain Eukarya Heterotrophic, eukaryotic organisms that secrete enzymes in order to feed; in Domain Eukarya Plantae Photosynthetic, eukaryotic organisms that are autotrophic; in Domain Eukarya Very diverse group; all animals are eukaryotic and heterotrophic and exist nearly every part of the planet; fall under Domain Eukarya The End • PLEASE STUDY ~ QUIZ NEXT CLASS!