CLASSIFICATION SYSTEMS

2.5 MILLION SPECIES

WITH MILLIONS MORE NOT EVEN DISCOVERED

STANDARDS FOR CLASSIFYING

n ALL ORGANISMS ARE ASSIGNED A UNIVERSAL NAME

n ALL ORGANISMS ARE CLASSIFIED INTO A GROUP ACCORDING TO THEIR BIOLOGICAL CHARACTERISTICS

HISTORY

n By the 18th century all organisms were named

– names were based on the Latin or Greek language

n Early names were very long and usually were a description of the organism

History Continued:

n The first person to try and group organisms together was Aristotle (300bc)

-Group all things as plants or animals and then had sub-groups of each of those.

However, this system had many problems…but lasted for about 2000 years.

n Linnaeu came along in the 1700’s and developed a more useful system of naming.

Negatives of Aristotle’s System

n Did not group organisms according to their evolutionary history.

n Birds, bats, and flying insects are grouped together even though they are not related besides the fact that they can fly.

Current system

n BINOMIAL NOMENCLATURE

– Discovered by Carolus Linnaeus

• first part of name is the Genus name

– refers to a small group of organisms

• the second part of the name is the Species name

– usually a Latin word to describe the organism

– Always capitalize the Genus name, never the Species name

– Once names are given to organisms they are classified into Taxa (groups based on specific characteristics)

Positive aspects of Linnaeus’s system

n Eventually off of this system biologists began to realize that structural similarities reflect evolutionary relationships of a species.

– Example: Bats fly like birds but have hair and produce milk therefore, bats are mammals rather then birds.

– Basis of our modern system

Latin

n Language of scientific names

n Required to give each newly discovered species a Latin name.

n Why?

– No longer used in conversation and does not change

– Should be italicized and underlined when hand written

Common names

n Many organisms have common names just like a nick name for a friend.

n Can be misleading

– Example: Sea horse

– Example: Different names in different languages

Expanding on Linnaeus

n Taxonomists try to identify the underlying natural relationships between organisms

n Compare

– Internal structure

– External structure

– Geographical distribution

– Chemical makeup

Taxonomy a useful tool

Useful for many types of occupations

Agriculture

Why?

Forestry

Why?

Medicine

Why?

Taxonomic rankings

Organisms are ranked in arbitrary taxa that range from having very broad characteristics to very specific ones.

Fit together like nesting boxes of increasing size

Same species=Organisms that look alike and can breed

The Large Taxa

n Species-Look alike and successfully interbreed

n Genus-A group of similar species that have similar features and are closely related

n Family-Share certain characteristics

n Order-A taxon of similar families

n Class-Taxon of similar orders

n Phylum-A taxon of similar classes

n Kingdom-Taxon of similar phyla

TAXA GROUPS

n KINGDOM:

– Largest group consisting of all organisms from phylum on down the continuum

– example: Animalia -all animals

n PHYLUM:

– groups of several classes consisting of very different organisms but they share some common characteristics

– example: backboned

n CLASS:

– groups of orders in which organisms share some very basic similiarities

– example: warmblooded, body hair, milk glands

n ORDER:

– Consists of several families that contain many characteristics in common

n FAMILY:

– Larger taxon than a genus that contains all organisms within a certain group

n GENUS:

– larger group of organisms containing many similar characteristics

n SPECIES:

– smallest taxon consisting of a group of very similar organisms that can successfully breed

– Sub-species: variations of species

Evolutionary Relationships:

Organisms are classified into each of the different taxa based on their relationship to one another.

Focusing on:

n Structure, breeding behavior, geographical distribution, chromosomes, and biochemistry.

– Structure: Having similar structures (implies that species have evolved from a common ancestor).

– Breeding behavior: Similar looking species may have completely different breeding patterns, and thus maybe different species.

– Geographical Distribution: Where a species is on the planet may

The Six Kingdoms

n Archaebacteria

n Eubacteria

n Protists

n Fungi

n Plants

n Animals

THE KINGDOMS

n The first system only contained 2 kingdoms

n the system expanded to 5 kingdoms, but the Monera kingdom was broken down again

Prokaryotes

n Organisms with cells that lack distinct nuclei bounded by a membrane

– Archaebacteria

• Contain a few hundred species

• Most live in extreme oxygen free environments

– Eubacteria

• Contain over 10000 species

• Live in most environments

• Most are harmless, but some are not

Protista

n Are eukaryotic

– contain a nucleus and mitochondria

n Are single celled

n Some contain chloroplasts

n 3 groups
animal like, plant like, fungus like

n dividing lines and characteristics are not clear-cut

Fungi

n Build cell walls that do not contain cellulose

n heterotrophic

– do not photosynthesize

n have nuclei, but are not always seperated by cells

Plantae

n Multicellular

n have cell walls that contain cellulose

n autotrophic

Animalia

n Mulicellular

n heterotrophic

n no cell walls