Taxonomy – the branch of biology that names and groups organisms according to their characteristics and evolutionary history. (Holt)

Through taxonomy scientists classify organisms and assign each organism a universally acceptable name. (Prentice Hall)

ScientistsAristotle – over 2000

years ago, he developed

the first system of classification.

He divided all living

organisms into two

categories:

Plants and animals.

Aristotle’s Classification Scheme

Plants were divided into three groups: herbs with soft stems, shrubs, and trees with a single wood stem.

Animals were divided into land dwellers, water dwellers and air dwellers.

He devised a system

of grouping organisms

into hierarchical categories.

He used structure and form

of organisms (morphology)

to help classify them.

Linnaeus’s Linnaeus’s Levels of

Classification

Linnaeus developed a system of seven levels or “taxa” (singular = taxon).

The levels are grouped from the largest most inclusive group to the smallest most exclusive group.

Seven Levels of Taxonomy:

• 1- Kingdom

• 2- Phylum (or Division)

• 3- Class

• 4- Order

• 5- Family

• 6- Genus

• 7- Species

DOMAIN

Scientific Names Linnaeus also developed a system of naming

called Binomial Nomenclature in which the species name of an organism is made up of two parts: the genus name & the species identifier.

• Example: Grizzly bear

(common name)

binomial nomenclature

= Ursus arctos

(usually in italics, first word capitalized.)

Why do scientists avoid using common names when discussing

organisms?

Common names can be confusing because they may vary among languages and even among regions in a single country.

Example: A cougar • is a puma, • is a mountain lion• is a catamount • is a ghost cat

Pyractomena borealis(example of scientific name)

Common names: Lightning bugs

Glowworms, or Fireflies (They are not

really flies – they are beetles. Flies have one pair of wings, while other winged insects have two or four pairs of wings. When the name of an insect contains the word fly, such as dragonfly, or firefly, they are not flies.)

Examples of other Firefly Genera.

Lamprocera – brilliant and wax-colored

Microphotus – small light

Macrolampis – big light

Pyrogaster – fire stomach

Lampyris – glowworm

Pyropyma – fire butt

Sometimes different species can share the same common

name:• United Kingdom: Buzzard = Hawk

• United States: Buzzard = Vulture

Other Examples:• Humans = Homo sapiens

• Lion = Panthera leo

• House cat = Felis domesticus

• Domesticated dog = Canis familiaris

• Red Maple Tree = Acer rubrum

Six Kingdom System:• Archaebacteria = unicellular prokaryotes

(descended from & very similar to first cells)

• Eubacteria = unicellular prokaryotes (most bacteria that affect you)

• Protists = protozoans & algae

• Fungi = fungi

• Plantae = plants

• Anamalia = animals

Traditional classification relied primarily

on body characteristics.

Biologists now group organisms into categories that represent lines of evolutionary descent, as well as physical characteristics.

DNA analysis is an important tool in classification science. It can be used to show how closely related organisms may be.