Copyright 2010. PEER.tamu.edu

Why classify things?Say you go to the mall to get some new

clothes.Where would you go?How would you know to go to that particular

store?

How is a mall organized?Food CourtBig Department StoresSpecialty Clothing StoresJewelry StoresElectronics StoresShoe StoresToy StoresKiosks

Can you imagine if the mall was just one big store and you had to go through rows and rows of “stuff” to find the right clothes in the right brand and the right size for you?

How long would that take?

Big Idea:The mall, your city, your

school, and your closet (hopefully) are all organized so that you and other people can get things done without wasting extra time and effort.

Scientists also organize or classify things so that they are easier to investigate and understand.

Here are some things that scientists classify or organize:

The human body

The elements

Interactions in Ecosystems

Scientists also Classify Living Organisms

How could you classify these living things?

Quick, organize these living things into groups:

Did you do it like this?

Or this?

Are there any other ways to group these living things?

Veterinarians classify organisms for many reasons:Veterinarians have to classify infectious

organisms so that they can understand how to treat them, according to their characteristics. It is important to know if they are bacteria, protozoa, prions, or viruses.

Veterinarians have to classify their patients so that they can understand how their patients’ body systems work and how to treat those systems. Different species, and even different breeds, react differently to treatment.

The most basic classification system is based on Domains and Kingdoms. Organisms are classified into Domains or Kingdoms based on these characteristics:1. Whether they are unicellular or multicellular2. Whether they are prokaryotic or eukaryotic3. Whether they have a cell wall or cell membrane4. Whether they have membrane bound organelles5. Whether they are autotrophic or heterotrophic6. Whether they reproduce sexually or asexually7. How they tolerate heat, salt, or other extreme

conditions

Basic ClassificationDomains:There are three

Domains of living organisms based on their characteristics:

Archaea (also called Archaebacteria)

Eubacteria (also called Bacteria)

Eukaryota (also called Eukarya)

Archaea

Eubacteria Eukaryot

a

Basic ClassificationKingdoms:The Domains can also be split into Kingdoms

which further divide the organisms by their characteristics.

Domain Archaea

“Archaea” means “ancient” bacteria.Organisms in Archaea are:UnicellularProkaryoticAutotrophic or heterotrophicOrganisms that reproduce asexuallyBacteria that have adapted to extreme

environments. Some can survive in extremely hot environments,

like around hot springs and geysers. They are called thermophiles.

Some can survive in extremely salty environments, like The Great Salt Lake in Utah. They are called halophiles.

The Domain Archaea has one Kingdom, also called Archaea

Aerial view of hot spring at Yellowstone

This hot spring is flowing into the Firehole River in Yellowstone. The colors are caused by different varieties of archaebacteria and other microscopic life forms. Scientists can distinguish temperatures of water by the colors present.

Domain Eubacteria

“Eu” means “true” bacteria. They are:

UnicellularProkaryoticAutotrophic or heterotrophicOrganisms that reproduce

asexuallyThe most abundant organisms on

earth. One bacterium can give rise to 10 million in 24 hours.

Found in almost every habitat on earth.

The Domain Eubacteria has one Kingdom, also called Eubacteria.

Many are common infectious agents.

This is a picture of bacteria on the skin. Bacteria can be shaped like a sphere (cocci) like this picture, like a rod, or like a spiral. The structure in the middle of

this picture is a hair follicle with a hair growing out of it.

Terminology:

The Domains Archaea and Eubacteria are commonly grouped together in discussion and calledprokaryotes because they lack membrane-bound nuclei and membrane-bound organelles. Nucleus

and Organell

es

Domain Eukaryota (Eukarya)EukaryoticVery diverseUnicellular or multicellularAutotrophic or heterotrophicReproduce sexually or

asexuallyCan be split into 4 Kingdoms-

ProtistaFungiPlantaeAnimalia

The 4 Kingdoms in EukaryotaProtistaMostly unicellular and microscopicAutotrophic or heterotrophic Can be infectious agents

Examples:•Amoeba•Algae•Daphnia•Plasmodium (causes malaria)

PlantaeMulticellular green plantsAutotrophic through photosynthesisHave a cell wall

Examples:•Mosses•Ferns•Trees•Flowering Plants

FungiMulticellularHeterotrophicDecomposersCan be infectious agents

Examples:•Mushrooms•Athlete’s foot•Bread Mold

AnimaliaMulticellular AnimalsHeterotrophicNo Cell Wall

Examples:•Insects •Spiders•Crabs•Birds•Humans

DOMAINS

KINGDOMS

Think Break:

Where do Viruses fit in this classification system?

Where do Prions fit in this classification system?

How would you classify these?A organism that can exist in extremely hot

temperatures and that is made of only one cell with no nucleus

Domain: Archaea Kingdom: Archaea

A green organism growing from the ground that is multicellular and that undergoes photosynthesis; its cells have nuclei and cell walls

Domain: Eukaryota Kingdom: Plantae

Try two more:This microscopic and one-celled organism lives in

colonies with millions of others like it. It does not have a nucleus and cannot survive in extreme conditions. It could be an infectious agent.

Domain: Eubacteria Kingdom: Eubacteria

This organism is a multicellular decomposer; its cells have nuclei.

Domain: Eukaryota Kingdom: Fungi

Classification Systems Can Change!Can you guess why?

Classification systems change as new organisms are discovered and as more information is gained about known living organisms.

Science is a “work in progress” and things change as new evidence is found.

Even though classification is not an exact science, it is a part of almost

every aspect of our lives.

Which one would you choose? Why?