18-1 Finding Order in Diversity

Biologists have identified and named 1.5 million species so far

Why Classify?

• To study the diversity of life, biologists use a classification system to name organisms and groupd them in a logical manner.

• In the discipline known as taxonomy, scientists classify organisms and assign each organism a universally accepted name

Assigning Scientific Names

• To avoid confusion, scientists agreed to use a single name for each species. Because 18th century scientists understood Latin and Greek, they used those languages for scientific names

Early Efforts at Naming Organisms

• It was difficult to standardize the names of organisms because different scientists described different characteristsics

• For example, an English scientist might call one species of oak as “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges

Carolus Linnaeus (botanist)

Binomial Nomenclature

• Carolus Linnaeus, a Swedish botanist developed a two-word naming system called Binomial Nomenclature, a system still in use today.

• The scientific name is always written in italics. • The first word is capitalized, the second word

is lowercased

Binomial Nomenclature

• The first part of the scientific name is the genus to which the organism belongs. A genus is a group of closely related species

• The second part of the scientific name describes the species

Binomial Nomenclature

Ursus arctos Ursus maritimus

Linnaeus’s System of Classification

• Linnaeus’s hierarchical system of classification includes seven levels. They are-from smallest to largest-species, genus, family, order, class, phylum, and kingdom.

• In taxonomic nomenclature, each of these levels is called a taxon, or taxonomic category

Linnaeus’s System of Classification

• Genera that share many characteristics are grouped in a larger category, the family

• An order is a broader taxonomic category consisting of many families

• The class is composed of similar orders• Several different classes make up a phylum• The kingdom is the largest taxonomic category

Linnaeus’s System of Classification