Pages
28-29
Chapter 1
Classifying
Living Things
Lesson 1
How Are Living Things Classified?
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Cute.. but SMELLY!
Don’t bother this mother skunk and her young! If you do,
you’ll be covered with an oily liquid whose bad smell will
stay with you for a long time! 
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How many kinds of animals and plants would you see in a park or in the
ocean? There are millions of different kinds of organisms in the world.
An organism is a living thing. Scientists study organisms to find out
how they live and then classify them into groups that are alike.
There are many ways to group organisms. Organisms that live in the
ocean may be grouped together. You might group living things by how
they move.
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At first, scientists classified organisms by how they got their food.
They put all living things into either the animal kingdom or the
plant kingdom. Animals—move to get food. Plants—make their
own food but can’t move. This way to classify worked for most
living things, but not for all. For example, fungi can’t move, and
they also can’t make food. So they became their own kingdom,
the fungi kingdom.
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When microscopes were invented, scientists found organisms that
had never been seen before. Organisms that cannot be seen with
the eyes alone are microscopic.
Most microscopic organisms have one cell, unlike plant and
animal cells. These one-celled organisms are in the Bacteria &
Protist kingdoms.
Organisms are now classified by what their cells look like.
When Linnaeus developed his system of classification, there were
only two kingdoms, Plants and Animals. But the use of the
microscope led to the discovery of new organisms and the
identification of differences in cells. A two or three-kingdom
system was no longer useful.
Today the system of classification includes six kingdoms.
The Six Kingdoms:
1. Plantae (Plants)
2. Animalia (Animals)
3. Protista (Protists)
4. Fungi
5. Archaebacteria,
6. Eubacteria
The Six Kingdoms
of Life
BrainPOP Video
Every part of you is made of cells.
• All cells have a cell membrane.
Materials needed by the cell pass
into the cell through the cell
membrane.
• In the mitochondria, activities are
carried out that release energy for
the cell.
• The nucleus controls all functions
of an organism. Sometimes called
the “BRAIN” or “BOSS”
Cells make new cells by dividing.
All the material in a cell is split
between two new cells.
The cell to the right is an
animal cell.
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Plant cells have all of
the same parts as
animal cells. However,
they differ in some ways.
• Plant cells are
surrounded by a stiff
cell wall.
• Plant cells also have
chloroplasts, where
food is made.
Bacteria cells have
cell walls, as do
plant cells, but
bacteria cells do not
have a nucleus.
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Bacteria are the most numerous organisms on
Earth.
• Bacteria are commonly grouped by their
shape.
• Some are rod-shaped
• Some are round
• Some are spiral-shaped
Some bacteria live as individuals. Others
cluster together in pairs or chains. Some
colonies are large enough to be seen.
Some bacteria cause disease. When you
scrape your knee, bacteria may cause infection.
So, it’s important to do what?
Most bacteria are useful—help digest food
and clean up oil spills.
Protista (Protists)
• There are more than 80,000
kinds of protists. Algae and
protozoans make up the
protists.
Algae are found in fresh and salt water
everywhere in the world. Algae also grow on
rocks and trees and in moist soil.
Protozoans, like animals, hunt and
gather food. They eat other protists
and bacteria. The amoeba is a type of
protozoan. The picture to the right
shows 2 amoebas. One amoeba is
eating an algae cell.
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