ClassificationTo avoid confusion caused by regional names, biologists use a classification

system to group organisms in a logical manner and to assign names.

Linnaeus developed the method used to name organisms and group them in a

logical manner which gives a universally accepted name.

the scientific name is the universally accepted name given to every species.

– the system of naming organisms according to genus and species

Taxonomy is used to classify and assign each organism a universally accepted name.

In taxonomy, each level is called a taxon: Kingdom Phylum Class Order Family Genus Species

binomial nomenclature

Linnaeu’s hierarchial system of classification

Grizzly bear Black bear Red foxPanda bear

Abert squirrel

Coral snake Sea

Star

Kingdom

Phylum

C;lass

Order

Family

Genus

Species

Animalia

Chordata

Mammalia

Carnivora

Ursidae

Ursae

Ursus arctos

Which Similarities Are Most Important?

Early systems of classification grouped organisms together based on visible similarities

Modern Evolutionary Classification

appendages Conical shell

Organisms are grouped into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities

Phylogeny – evolutionary relationships among organisms

Evolutionary Classification

A cladogram is a diagram that shows evolutionary relationships among organisms based on shared derived characters.

Classification Using Cladograms

Similarities at the DNA level in the genes of organisms can be used to help determine classification

Similarities in DNA and RNA

African vultureAmerican vulture

Marabou stork

The American vulture and the Marabou stork are more closely related than the American vulture and the African vulture

◦ By comparing the DNA sequences of two or more species, biologists estimate how long the species have been separated

Molecular Clocks

The three-domain system was first invented in 1990, but not generally accepted until later.

One main characteristic of the three-domain method is the separation of Archaea and Bacteria◦ previously grouped into the single kingdom

Bacteria (also called Monera).

three-domain system

Archaea are the most ancient organisms on Earth and they exist in extreme environmentsStreptococcus bacteria can live in a persons body and cause illnesses like strep throat

The majority of biologists accept the domain system, but a large minority use the five-kingdom method.

three-domain system

Extremophiles

Extremophilic microbes can be found thriving in some of the most hostile environments imaginable —

swimming in near-boiling water eating rocks

in subzero temperatures where radiation levels rival nuclear reactors

An extremophile is an organism that thrives under "extreme" conditions.

The term frequently refers to prokaryotes and is sometimes used interchangeably with Archaea. extremophiles come in all shapes and sizes

our understanding of the diversity of extreme habitats increases daily.

What is an Extremophile?

They are a combination of the suffix –phile, meaning "lover of," and a prefix specific to their environment. For example, acidophiles are organisms that love (phile) acid (acido).

Terms Used to Describe Extremophiles

Acidophile: An organism that grows best at acidic (low) pH values.

Alkaliphile: An organism that grows best at high pH values.

Anaerobe: An organism that can grow in the absence of oxygen.

In biology, binomial nomenclature is the formal system of naming specific species.

Each species name is in (modern scientific) Latin and has two parts, so that it is popularly known as the “scientific name " of the species.

The species is the lowest level in the system for classifying organisms.

Review

As the words "binomial", "binominal" and "binary" the scientific name of each species is formed by the combination of two words

the genus name (also called the generic name).

a second word identifying the species within that genus, (also called the specific epithat)

Genus and species

Species names are usually in italics; for example, Homo sapiens. When handwritten, they should be underlined; for example, Homo sapiens. Each name should be underlined individually.

The genus name is always written with an initial capital letter. ◦ For example, the entire tiger species is Panthera

tigris

Genus and species

Cladistics is the hierarchical classification of species based on evolutionary ancestry.

Cladistics is distinguished from other taxonomic systems because it focuses on evolution rather than similarities between species

Cladistics generates diagrams called cladograms that represent the evolutionary tree of life.

DNA and RNA sequencing data are used in cladistics.

The word cladistics is derived from the ancient Greek meaning "branch."

Cladistics

Kingdom Protista