Classification Evolution has lead to a staggering variety

Classification

• Evolution has lead to a staggering variety or organisms • Biologists have identified and named about 1. 5 million species so far • They estimate anywhere between 2 and 100 million additional species have yet to be discovered

Taxonomy • The science of classifying and naming organisms

Assigning Scientific Names • By the 18 th century, European scientists recognized that referring to organisms by common names was confusing • Common names vary among regions within a country

Mountain Lion

Cougar

Puma

Panther

Early Efforts at Naming Organisms • First attempts at standard scientific names often described physical characteristics • As a result, these names could be 20 words long! • Ex. ) The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges. ”

Binomial Nomenclature • Carolus Linnaeus (18 th Century) • Swedish Botanist • Developed a system for naming organisms

Binomial Nomenclature • Two word naming system

Rules for Binomial Nomenclature • Written in italics • First word is capitalized • Second word is lowercased Ex. ) Genus species G. species

• The name often tells you something about the species • Ex. ) Tyranosaurus Rex • Tyrant Lizard King

Taxon (taxonomic category) • A group or level of organization

Linnaeus’s system of classification uses seven taxonomic categories Kingdom Phylum Class Order Family Genus species Largest / Least Specific Smallest / Most Specific

Mnemonic Device Kingdom Phylum Class Order Family Genus species • • King Phillip Came Over For Good Soup

Evolutionary Classification • Darwin’s theory of evolution changed the entire way that biologists thought about classification • Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities

Derived characteristics • Characteristics that appear in recent parts of a lineage but not in its older members

Cladograms • Diagram that shows the evolutionary relationships among a group of organisms

• In taxonomy, as in all areas of science, ideas and models change as new information arises, some explanations have been discarded altogether, whereas others such as Darwin’s theory of evolution by natural selection, have been upheld • So it should not be surprising that since the 1800’s, the tree of life has been revised and edited since the discovery of all this new information

The Tree of Life Evolves • Before Linnaeus’s time, the only two Kingdoms that existed were Plants and Animals • As scientists discovered new organisms that didn’t fit into the plant or animal category, they made a new category

The Old 5 Kingdom System 1. 2. 3. 4. 5. Animals Plants Fungi Protist Bacteria

• In recent years, as evidence about microorganisms continued to accumulate, biologists come to recognize that the Monera were composed of two distinct groups

The New 6 Kingdom System 1. 2. 3. 4. 5. 6. Animals Plants Fungi Protist Eubacteria Archaebacteria

The Three Domain System • Molecular analysis has given rise to a new taxonomic category that is now recognized by many scientists

Domain • Larger than a kingdom

3 Domains 1. Bacteria • Eubacteria 2. Archaea • Archaebacteria 3. Eukarya • Protists, fungi, plants, animals (Everything with a nucleus)