Classification Notes

Taxonomy

• Naming and grouping organisms according to their characteristics and evolutionary history.

Aristotle

• Greek philosopher who first attempted to classify living organisms

• Over 2000 years ago

Aristotle

• He classified living things into two groups:– Plants – Animals

Aristotle

• Why did his system create problems?– Not all living things are

plants and animals– Even plants and

animals are very diverse

– Our knowledge of life has changed

Carolus Linnaeus

• Swedish scientist who developed our modern system of classification.

• 1707 - 1778

Carolus Linnaeus

• Used morphology (form and structure) to categorize organisms

Carolus Linnaeus• Developed a hierarchy of levels in his

system– Kingdom King– Phylum Phillip– Class Came– Order Over– Family For– Genus Good– Species Soup

Species

• Remember that a species is a group of organisms that can mate and reproduce fertile offspring

• Not a clear cut definition

Common Names

• Most people use common names for organisms

• This causes problems– 13 lined ground

squirrels are often called gophers

Scientific Names

• Scientific names solve the naming problem

• Latin is used for most scientific names.

Binomial Nomenclature

All organisms are given a genus and a species name.

This way all people can use the same name to identify organisms

Genus and Species• The genus name

comes first and begins with a capital letter.– Ex. Felis (it can be

abbreviated as F.

• The species names comes second and begins with a lower case letter.– Ex. domesticus *Both the genus and species

names are usually italicized and often underlined.Ex. Felis domesticus

How do we classify organisms today?

• Not so much on physical similarities (can be based too much on opinions).

• Scientific evidence is a better way to do this.

Evidence for Classification

• Chromosome Structure

• Biochemical Similarities

• Embryology

• DNA Sequencing

• Reproduction

Systems of Classification

• Linnaeus used 2 Kingdoms– Plant– Animal

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The Three-Domain System

The Three-Domain SystemMolecular analyses have given rise to a new

taxonomic category that is now recognized by many scientists.

The domain is a more inclusive category than any other — larger than a kingdom.

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The Three-Domain System

The three domains are:• Eukarya, which is composed of protists, fungi, plants,

and animals.• Bacteria, which corresponds to the kingdom

Eubacteria.• Archaea, which corresponds to the kingdom

Archaebacteria.

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Domain Bacteria

Domain BacteriaMembers of the domain Bacteria are unicellular

prokaryotes.

Their cells have thick, rigid cell walls that surround a cell membrane.

Their cell walls contain peptidoglycan.

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Domain Archaea

Domain ArchaeaMembers of the domain Archaea are unicellular

prokaryotes.

Many live in extreme environments.

Their cell walls lack peptidoglycan, and their cell membranes contain unusual lipids not found in any other organism.

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Domain Eukarya

Domain EukaryaThe domain Eukarya consists of organisms that

have a nucleus.This domain is organized into four kingdoms:

– Protista– Fungi– Plantae– Animalia

Modern Kingdoms

• Animalia

• Plantae

• Fungi

• Protista

• Archaebacteria

• Eubacteria

Animalia

• Multicellular heterotrophs

Plantae

• Multicellular autotrophs

Fungi

• Most are multicellular• Yeast is unicellular• Absorb food through

cell walls

Archaebacteria

• Unicellular prokaryotes

• Related to first life forms

• Live in harsh environments

Eubacteria

• Unicellular prokaryotes

• Includes most bacteria

Classification of a human

• Kingdom = Animalia• Phylum = Chordata• Class = Mammalia• Order = Primate• Family = Hominid• Genus = Homo• Species = sapien