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Classifying Organisms
Lesson One
How do Scientist Classify Organisms?
The Six Kingdoms
Scientist use a system of biological classification to keep
track of millions of different species. This system is a
way to put species into groups.
 kingdom – the highest level of biological classification
Scientist study the external and internal structure of
living things to group them. They use this information
to group species according to how closely they are
related.
Six Kingdoms
Six Kingdoms of Living Things
Kingdom
Description
Examples
Archaebacteria
One-celled,
Simple cells;
Make their own food
Eubacteria
One-celled,
Simple cells;
Some make own food
Protists
Most one-celled,
Complex cells;
Some make own food
Fungi
Most have many cells; Mushrooms,
absorb food from
mold, mildew
surroundings
Plants
Many cells,
Make own food
Moss, grass,
trees
Animals
Many cells,
Do not make own food
Worm, ant
frog, humans
Algae,
amoebas
Classifying

To group organisms, scientist classify
organisms in 4 ways:
1. external structures
2. internal structures
3. cells
4. chemical processes inside cells
How do scientist classify?
Scientist use a process called dichotomous key to
identify living things. The word dichotomous
means “divided into two parts”. The key gives
two characteristics to choose between. These
choices help scientist determine what the
organism can be.
 dichotomous key - a tool used to identify
organisms based on a contrasting pair of
characteristics
Bacteria - (Have 2 Kingdoms)


Bacteria - Small, single-celled organisms that
do not have a nucleus.
Bacteria are the most numerous kind of
organism.
Archaebacteria
Eubacteria
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Archaebacteria
1. Archaebacteria
In 1983, scientists tool samples from a spot deep
in in the Pacific Ocean.
n
These bacteria have lived on Earth longer than any
other organism.
**Some kinds live only where there is no oxygen and other
kinds live in areas where the heat is so high that most life forms
can’t survive.
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Eubacteria
Eubacteria are also complex and single celled. Most bacteria are in the
EUBACTERIA kingdom. They are the kinds found everywhere and are the
ones people are most familiar with.
.
Most eubacteria are helpful. Some
produce vitamins and foods like
yogurt. However, these eubacteria,
Streptococci pictured above, can give
you strep throat!
Protists
Protists - A single-celled or multi-cellular
organism that may share characteristics with
plants, fungi, and animals.
Protist cells have a nucleus,
and their structures have 2 or more parts.
Protists cells have a nucleus, and other
structures have 2 or more parts.
Fungi
Fungi - A kingdom of organisms, with
a nucleus, that get nutrients by
decomposing other organisms.
Some fungi taste great and others can kill you!
Fungi are organisms that biologists once
confused with plants, however, unlike plants,
fungi cannot make their own food. Most
obtain their food from parts of plants that are
decaying in the soil.
Mushrooms, mold and mildew are all examples of
organisms in the kingdom Fungi.
**Fungi grow fast and reproduce by spores.
Plants
Plants have many cells.
Most plants make their own food using the
Sun’s energy and have a nucleus.
They have tissues, organs, cell walls, and
chloroplasts.
They are classified according to the ways they
transport water and reproduce.