Classification

Classification

• Over 2 million species of organisms have been found and named

• Thousands of new species are being discovered each year

• There may be as many as 50 million species left to find (or more)!

Taxonomy1. Putting organisms

in groups (taxons) based on their characteristics

2. Naming organisms

Aristotle’s SystemAristotle was the 1st to do detailed work on

classification. He divided animals into two groups:– Animals with blood

• Mammals• Birds• Reptiles• fish

– Animals without blood• Insects • worms

LinnaeusCame up with:• a system to NAME organisms

• A system to CLASSIFY organisms (place into groups)

• Based his groups on morphology

• Each group called a taxon

Taxonomic Groups

KingdomPhylum

ClassOrder

Family Genus

Species

Binomial Nomenclature

• System of naming organisms

• Each organism is given a two part name

Genus species

Ursus arctos

People• Kingdom Animalia• Phylum Chordata• Class Mammalia• Family Hominidae• Genus Homo• Species sapiens

• Scientific name: Homo sapiens

Modern System

• Very similar to Linnaeus

• Based on supposed evolutionary relationships – (phylogeny) not just physical similarities

• Cladograms show these relationships

Cladograms

All living organisms are now classified into one of 6 kingdoms:

Kingdom Archae-

bacteria

Eu-bacteria

Protista Fungi Plantae Animalia

Cell Type

# cells

Mode of nutrition

See class handout or see page 459 in textbook

6 kingdoms

All living things fall into 1 of these 6 kingdoms

Dichotomous Keys

• Series of paired statements to identify organisms (p. 462)