Classification of

Organisms

How many different types of organisms are there on Earth?

More than 2 million!

• Tremendous diversity

• Scientists estimate between 2 and 100 million species yet to be discovered

What is classification?• Classification

– a systematic arrangement of organisms into groups or categories according to specific scientific criteria

• Taxonomy – science of classifying organisms

Why Classify?• Set up an organized

system so scientists can communicate

• Study similarities and propose relationships between organisms

• Show evolutionary linkages between organisms

Common Names• One species can have many different

names– Example:

Mountain lion, puma, cougar, or panther?•Vary among languages and

regions

Early Efforts at Naming Organisms

• Described the PHYSICAL characteristics– Example: Oak with deeply divided

leaves that have no hairs on their undersides and no teeth around their edges

• Different scientists described different characteristics

• Swedish botanist• Based his system on

STRUCTURAL similarities• Developed a ranking

system that went from broadest to most specific

• The father of modern taxonomy

Carlos Linnaeus

Binomial Nomenclature• The system used to

identify all organisms using a two part Latin name

• Each SPECIES is assigned a two-part name– Population of organisms

that share common characteristics and breed to produce fertile offspring

Keys to Binomial Nomenclature

Felis domesticus• Name has 2 part – Genus & species• Must be in italics or underlined• Genus (1st word) must be

capitalized• Species must be lowercase

Correct or Incorrect?•Triticum Aestivum - wheat •Felis domesticus - cat •canis lupus - wolf •Canis familiaris - dog •Populus deltoides -

cottonwood

Hierarchy of Classification• Kingdom• Phylum• Class• Order• Family• Genus• Species

• King• Philip • Came• Over• For • Good• Soup

Linneaeus’s Hierarchy of Classification

• Kingdom• Phylum• Class • Order• Family• Genus• Species

• King • Phillip• Came • Over • For• Good • Soup

Classification Example

• Kingdom – Animalia– Multicellular– Heterotrophic

Classification Example

• Phylum – Chordata– Nerve cord

Classification Example

• Class – Mammalia– Mammary glands– Breathes air– Four-chambered hearts– Endotherms (generate

internal body heat)

Classification Example

• Order – Perissodactyla– Hooves– Odd number of toes on

each foot– Herbivore

Classification Example

• Family – Equidae– Long heads and necks– Mane– Long slender tails

Classification Example

• Genus – Equus– Three toes

Classification Example

• Species – grevi– Distinctive striping pattern,

with black stripes separated by narrow white bands

– Stripes continue down the legs to the hooves.

– There is a distinctive pattern on the hind quarters

Who am I?Equus grevi

How do scientists classify new organisms?

• They study their characteristics

• They try to see if they are similar to other already known organisms

• They group a new organism with others that have similar characteristics

Summary• Scientists use Linnaean classification

system to group organisms• Organisms are grouped based on

structural characteristics and information from all scientific fields

• Levels of classification start in large non-specific groups and end in small specific groups