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Chapter 18 Classification Section 18-1 • Why Classify? • Because of the diversity and number of organisms on planet Earth. • Each organism need a name, and it needs to be organized into groups that biological meaning. • Taxonomy-scientists classify organisms and assign each one a universally accepted name. • Carolus Linnaeus developed a two-word naming system called binomial nomenclature. We still use this system today. • Each species is assigned a two-part scientific name. It is always written in italics. The first word is capitalized, and the second word is lowercase. • The name for a grizzly bear, Ursus arctos, is one example. • The first name, Ursus, is the genus name. Genus is a group of closely related species. The genus Ursus contains 5 other types of bears, including polar bears. • The second part of the name, arctos, is the species name. • Linnaeus’s classification system is hierarchical, which means it consists of levels. • There are 7 levels, and the list is from largest to smallest: • Kingdom, Phylum, Class, Order, Family, Genus, Species. • Each of the 7 is known as a taxon, which is a taxonomic category. • Family-A group of genera that share many characteristics. Example: Bears are in the family Ursidae. • The bears, along with 6 other families of animals, such as dogs (Canidae) and cats (Felidae) are grouped together in the Order Carnivora. An Order is a broad taxonomic category made of similar families. • Class is the next larger category. It is made up of similar Orders. • Example: The order Carnivora is placed in the class Mammalia, which includes animals that are warm blooded, have body hair, and produce milk for their young. • Several different classes make up a Phylum (plural Phyla). It includes many different organisms that share important characteristics. • The largest group is Kingdom. All animals are placed in the kingdom Animalia. Flowchart Section 18-1 Linnaeus’s System of Classification Kingdom Phylum Class Order Family Genus Species Figure 18-5 Classification of Ursus arctos Section 18-1 Grizzly bear Black bear Giant panda Red fox Coral Sea star Abert squirrel snake KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos • Phylogeny: the study of evolutionary relationships among organisms. • Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. This is known as evolutionary classification. • This studies how long ago organisms have had a common ancestor. • The assumption in evolutionary classification is that new and better traits arise over long periods of time. • Derived Characteristics are those that appear in recent parts of a lineage or line but are not present in older more distant times. • A Cladogram is a diagram that shows the evolutionary relationships in a group of organisms. Traditional Classification Versus Cladogram Section 18-2 Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM Traditional Classification Versus Cladogram Section 18-2 Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM The Kingdoms • Before the 1990’s, there were only thought to be 5 kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. • During the 1990’s, a sixth kingdom was added as Monera was split into 2 new kingdoms: • Eubacteria, Achaebacteria, Protista, Fungi, Plantae, and Animalia. Figure 18-12 Key Characteristics of Kingdoms and Domains Section 18-3 Classification of Living Things DOMAIN Bacteria Archaea KINGDOM Eubacteria Archaebacteria CELL TYPE Eukarya Protista Fungi Plantae Animalia Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote Cell walls with peptidoglycan Cell walls without peptidoglycan Cell walls of cellulose in some; some have chloroplasts Cell walls of chitin Cell walls of cellulose; chloroplasts No cell walls or chloroplasts Unicellular Unicellular Most unicellular; some colonial; some multicellular Most multicellular; some unicellular Multicellular Multicellular MODE OF NUTRITION Autotroph or heterotroph Autotroph or heterotroph Autotroph or heterotroph Heterotroph Autotroph Heterotroph EXAMPLES Streptococcus, Escherichia coli Methanogens, halophiles Amoeba, Paramecium, slime molds, giant kelp Mushrooms, yeasts Mosses, ferns, flowering plants Sponges, worms, insects, fishes, mammals CELL STRUCTURES NUMBER OF CELLS Domains • The Domain category is more inclusive and is larger than a Kingdom. • At this point in time there are 3 Domains: Eukarya, Bacteria, and Archaea. Figure 18-13 Cladogram of Six Kingdoms and Three Domains Section 18-3 DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms DOMAIN BACTERIA Eubacteria Archaebacteria Protista Plantae Fungi Animalia