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 Court
 Big Department Stores
 Specialty Clothing Stores
 Jewelry Stores
 Electronics Stores
 Shoe Stores
 Toy Stores
 Kiosks
 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 elements
 The human body
 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 multicellular
2. Whether they are prokaryotic or eukaryotic
3. Whether they have a cell wall or cell membrane
4. Whether they have membrane bound organelles
5. Whether they are autotrophic or heterotrophic
6. Whether they reproduce sexually or asexually
7. How they tolerate heat, salt, or other extreme
conditions
Basic Classification
Domains:
Archaea
 There are three Domains
of living organisms based
on their characteristics:
 Archaea (also called
Archaebacteria)
Eubacteria
Eukaryota
 Eubacteria (also
called Bacteria)
 Eukaryota (also
called Eukarya)
Basic Classification
Kingdoms:
The Domains can also be split into Kingdoms which
further divide the organisms by their characteristics.
Domain Archaea
Aerial view of hot spring at Yellowstone
“Archaea” means “ancient” bacteria.
Organisms in Archaea are:





Unicellular
Prokaryotic
Autotrophic or heterotrophic
Organisms that reproduce asexually
Bacteria 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
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:
 Unicellular
 Prokaryotic
 Autotrophic or heterotrophic
 Organisms that reproduce asexually
 The 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 called
prokaryotes because they lack membrane-bound
nuclei and membrane-bound organelles.
Nucleus
and
Organelles
Domain Eukaryota (Eukarya)
 Eukaryotic
 Very diverse
 Unicellular or multicellular
 Autotrophic or heterotrophic
 Reproduce sexually or asexually
 Can be split into 4 Kingdoms Protista
 Fungi
 Plantae
 Animalia
The 4 Kingdoms in Eukaryota
Protista
Plantae
Mostly unicellular and microscopic
Autotrophic or heterotrophic
Can be infectious agents
Multicellular green plants
Autotrophic through photosynthesis
Have a cell wall
Examples:
•Amoeba
•Algae
•Daphnia
•Plasmodium (causes malaria)
Examples:
•Mosses
•Ferns
•Trees
•Flowering Plants
Fungi
Animalia
Multicellular
Heterotrophic
Decomposers
Can be infectious agents
Multicellular Animals
Heterotrophic
No Cell Wall
Examples:
•Mushrooms
•Athlete’s foot
•Bread Mold
Examples:
•Insects
•Spiders
•Crabs
•Birds
•Humans
D
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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?