Classifying Organisms What are living things, and how can they be classified? binomial nomenclature species genus dichotomous key cladogram Classifying Living Things Classification: organizing information based on characteristics or traits There have been many different ideas about how to organize, or classify, living things. Aristotle: Greek philosopher 384-322 BC 2 large groups plants and animals Based groups on size, shape, environment, presence of red blood cells Carolus Linnaeus classified organisms into two main groups, called kingdoms, based on similar structures. Animal and Plant Binomial nomenclature is a system for naming organisms with two-word scientific name Ex. Ursus arctos Robert H. Whitaker- 1969 created 5 kingdom system for classifying organisms Systematics- current system Carl Woese and George Fox uses all known evidence to classify organisms, including cell type, how food and energy are obtained, structure and function of features, common ancestry, and molecular analysis. Domain-A broad category of living things based on characteristics of the cell A level above Kingdom in classification created in 1977 based on DNA and cell type Prokaryotic cells: no nucleus, simple and small in size Eukaryotic cells: nucleus, complex and larger in size 1
10/2/2012 Domain: Archaea Means ancient Ancient Earth Prokaryotic cells Unicellular Extremeophyles: live in extreme conditions such as thermal vents deep in the ocean, hot geysers,with no oxygen, acidic conditions, salt, extreme cold Domain: Bacteria Prokaryotic Unicellular Live in most environments Helpful and harmful Genetically and chemically different than Archaea Domain Eukarya Eukaryotic cells cells with a nucleus and other organelles Multi-cellular and unicellular organisms More complex Larger Kingdoms: Animalia, Plantae, Fungi, Protista Organisms are now classified into one of three domains and then into one of six kingdoms. Determining Domains (cont.) What evidence is used to classify living things into groups? 2
Scientific Names Binomial nomenclature is a system for naming organisms with two-word scientific name: A species is a group of organisms that have similar traits and are able to produce fertile offspring. A genus is a group of similar species. Domain Kingdom Phylum Class Order Family Genus Species Scientific Names (cont.) genus from Greek genos, means race, kind Scientific Names (cont.) Binomial nomenclature was developed by Linnaeus and is still used today. Scientific names are important because each species has its own scientific name and those names are the same worldwide. 3
Genus group of species that have similar characteristics Members of a genus are closely related Ex. Ursus bears Ursus americanus Help to avoid errors in communication Organisms with similar evolutionary history are group together Allows information to be organized and easily found Descriptive information about species Elaphe guttata, Huernia guttata, Stephanorrhina guttata (guttata spotted) Ursus maritimus When naming an organism use both the genus and species name Writing names: Genus comes first & is capitalized and in italics species name comes second in lower case and italics- Both underlined when hand written Homo sapiens - humans Scientific Names (cont.) Why does every species have a scientific name? A dichotomous key is a series of descriptions arranged in pairs that lead the user to the identification of an unknown organism. A cladogram is a branched diagram that shows the relationships among organisms, including common ancestors. 4
All organisms are classified into one of three domains: Bacteria, Archaea, or Eukarya. Every organism has a unique species name. A dichotomous key helps to identify an unknown organism through a series of paired descriptions. How many scientific names does each organism have? A. 1 B. 2 C. 3 D. Many Which of these refers to the system for naming organisms with two identifying scientific terms? A. genus B. cladogram C. binomial domains D. binomial nomenclature 5
Which of these refers to the system for naming organisms with two identifying scientific terms? A. genus B. cladogram C. binomial domains D. binomial nomenclature Do you agree or disagree? 3. A dichotomous key can be used to identify an unknown organism. 4. Physical similarities are the only traits used to classify organisms. 6