Depending on where you live, this might be a mountain lion, cougar, puma, or panther – all of these are “common” names for the “Felis concolor”

Why Classify? To study the great diversity of organisms on the planet, biologists must give each organism a name. Biologists use a classification system to name organisms & group them in a logical manner.

Classification Taxonomy – The practice of naming & classifying organisms Scientists assign each organism a universally accepted name.

Biologists need a way to name organisms that does not depend on language or location. They group organisms into large & smaller, more specific categories called “taxa” (singular = taxon)

Scientific Nomenclature – biological system of naming 1750’s – Carl Linnaeus (Swedish biologist) wanted to catalog all known species. Came up with a 2-word Latin system called “binomial nomenclature.”

This unique 2-part name is called the “scientific name.” All scientific names are made up of 2 Latin words that consist of the genus name followed by the species name. Common Name: honeybee Scientific Name: Apis mellifera

Genus + species identifier (often descriptive) Genus – A level of classification that contains similar species. Common Name: cheetah Scientific Name: Acinonyx jubatus Common Name: leopard/panther Scientific Name: Panthera pardus Common Name: lion Scientific Name: Panthera leo

Naming Rules 1. All members of a genus share the genus name as the first term. 2. The 2 nd term is the “species identifier” and is often descriptive. 3. The genus is capitalized and the species identifier is lowercased. 4. Both terms should be italicized.

The Linnaean System Organisms are grouped at successive levels of a hierarchy based on similarities in their form & structure. 8 Basic Levels: domain, kingdom, phylum, class, order, family, genus, species

See page 425 in textbook

Levels of the Linnaean System ~Domain~ The most basic differences among cell types – 3 domains: 1. Bacteria – unicellular, prokaryotic, cells have cell walls, cell walls contain peptidoglycan (kingdom “Eubacteria”) 2. Archaea – same as bacteria but cell walls do not have peptidoglycan (a special protein). (kingdom “Archaebacteria”) 3. Eukarya – Consists of all organisms whose cells have a nucleus. Organized into 4 kingdoms of the 6 –kingdom system: (Protista, Fungi, Plantae, Animalia)

~Kingdom~ 6 large groups: Plantae, Animalia, Fungi, Protista, Archaebacteria, Eubacteria

Subgroup within a kingdom. ~Phylum~ Animal Phyla…

Subgroup within a phylum. ~Class~

Subgroup within a class ~Order~

Subgroup with order ~Family~

Subgroup within a family. Each genus is made up of species with uniquely shared traits. ~Genus~ African Wild dog – Family:canidae Genus:lycaon

~Species~ A unique group of organisms united by heredity and interbreeding.

“Modern Systematics”

How do we tell one species from another? Systematics is the study of biological diversity and its origins. It focuses on understanding evolutionary relationships among organisms such as genes, & the evolution of intrinsic traits, ecological interactions, & geographic distributions.

Scientists name & put organisms into groups based on their evolutionary history (how closely related they are). This is called “phylogeny.”

Phylogenetics Phylogeny is the grouping of organisms into categories that represent lines of evolutionary decent, not just physical similarities. It shows the ancestral relationships between species.

Phylogenetic Tree A diagram that shows the lines of evolutionary descent of different species, organisms, or genes from a common ancestor.

Misleading Similarities… Convergent evolution: Similarities may evolve in groups that are not closely related because they have adapted to similar habitats or lifestyles. (ex. Wings of a bird & wings of an insect)

Similarities that arise through convergent evolution are called “analogous characters.” Analogous structures have the same function (ex. wings for flight), while homologous structures have similar structure.

Cladistics An extremely similar method of classification is “cladistics.” Cladistics is a method of analysis that infers relationships by careful comparisons of shared characters (rather than by ancestors).

“Ancestral” vs. “Derived” Characters An ancestral character is thought to have evolved in a common ancestor of both groups. A derived character is one that evolved in one group but not in the other group… a new trait. An ancestral trait for the horse & monkey is that they have hair. A derived trait for the monkey is an “opposable thumb”

A “clade” is a set of groups that are related. Each clade is compared to an “outgroup.” The outgroup lacks some of the shared characteristics. (Think of it as a “basic” model – like a car before you add all the accessories)