18-1 Finding Order in Diversity Photo credit: ©Gary Randall/Visuals Unlimited Copyright Pearson Prentice Hall

18-1 Finding Order in Diversity Natural selection and other processes have led to a staggering diversity of organisms. Biologists have identified and named about 9 million species so far. They estimate that 2–100 million additional species have yet to be discovered. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Why Classify? Why Classify? To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Why Classify? In the discipline of taxonomy, scientists classify organisms and assign each organism a universally accepted name. Copyright Pearson Prentice Hall

Assigning Scientific Names Common names of organisms vary, so scientists assign one name for each species. Always in Latin. Genus species Homo sapiens Copyright Pearson Prentice Hall

Assigning Scientific Names Carolus Linneaus developed a naming system called binomial nomenclature. In binomial nomenclature, each species is assigned a two-part scientific name. The scientific name is italicized. Canis familiaris Felis catus Copyright Pearson Prentice Hall

Linnaeus’s System of Classification Linnaeus not only named species, he also grouped them into categories. What is Linneaus’s system of classification? Copyright Pearson Prentice Hall

Linnaeus's System of Classification   Linnaeus's seven levels of classification are—from smallest to largest— species genus family order class phylum kingdom Copyright Pearson Prentice Hall

Linnaeus's System of Classification  Each level is called a taxon, or taxonomic category. Species and genus are the two smallest categories. Grizzly bear Black bear Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall

Linnaeus's System of Classification Genera that share many characteristics are grouped in a larger category, the family. Grizzly bear Black bear Giant panda Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall

Linnaeus's System of Classification An order is a broad category composed of similar families. Grizzly bear Black bear Giant panda Red fox Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall

Linnaeus's System of Classification The next larger category, the class, is composed of similar orders. Grizzly bear Black bear Giant panda Red fox Abert squirrel Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Class Mammalia Copyright Pearson Prentice Hall

Linnaeus's System of Classification Several different classes make up a phylum. Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake PHYLUM Chordata Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall

Linnaeus's System of Classification The kingdom is the largest and most inclusive of Linnaeus's taxonomic categories. Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake Sea star KINGDOM Animalia Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall

Linnaeus's System of Classification Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake Sea star Linnaeus’s hierarchical system of classification uses seven taxonomic categories. This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category. Only some representative species are illustrated for each category above the species level. Copyright Pearson Prentice Hall