Name:__________________________________ Date:___________________ Period:___________
Unicellular Organisms
By Cindy Grigg
You know that living things are made of cells. Some animals and
plants are made of only one cell. They are called unicellular. Unimeans one as a unicycle has only one wheel. Most of us don't think
about these unicellular creatures very much, but they are all around
us. Most are invisible without a microscope, but a few may be visible to
the naked eye.
1
The main groups of unicellular organisms are bacteria, protozoa,
unicellular algae, and unicellular fungi or yeasts. Each species is unique, and they are
interesting to study because of their complex and beautiful patterns. Some unicellular organisms
are sensitive to light. They may move toward it or away from it, and they have ingenious ways of
moving around. They also respond to touch. Some can live in very hostile environments.
2
Single-celled organisms have been on earth for perhaps 3.8 billion years, so they have had
a long time in which to diversify. Scientists believe they were the first life-forms on Earth.
Although small, they are complex. They have ancient and effective means of survival. The more
that we learn about them, the more amazing we find them to be.
3
Some of their survival mechanisms have to do with their shapes. They may be spheres,
oblong, or spiral. A spherical shape resists drying out, something that would be fatal to a cell. An
oblong shape gives the cell more surface area for chemical exchanges with its environment. A
spiral shape makes it easier for the organism to move.
4
Unicellular organisms have unique ways to move. Some, such as euglena, have tiny hairlike fibers that are called flagella. These fibers thrash in the water and drive the cell forward. The
word flagellum means whip in Latin. Flagella (pronounced fla-jell-ah) is the plural form. Some
have groups or rows of tiny fibers that move together like oars in a sort of rippling pattern. These
are called cilia (pronounced silly-ah). Cells with cilia move fast! A paramecium is one unicellular
organism that moves with cilia.
5
Some unicellular organisms called amoebas are able to change their shapes. These "shapeshifters" can extend parts of themselves into what are called pseudopodia and then flow in the
direction in which they wish to go. Pseudopodia (pronounced sue-do-pode-ee-ah) means false
feet. If they find something to eat, they can engulf, or surround, the particle with their
pseudopodia. Then they pull themselves around it to digest it.
6
Just as the amoeba uses its pseudopodia both for movement and feeding, some unicellular
organisms with cilia also use the cilia to catch food. The stentor has cilia that beat rhythmically,
which draws food into its mouth. This is an adaptation that allows stentors to spend most of their
lives attached to a surface, saving their energy for catching food.
7
Some unicellular organisms live in extreme environments. Archaebacteria that like living in
such challenging places are called extremophiles(_______________________). They have
been found in such unfriendly habitats as Antarctic ice and in very hot deep-sea vents. The
ability of organisms to adapt to extremely hot or cold environments gives scientists hope that
signs of life will eventually be found on other planets. They have targeted Mars and Europa, an
icy moon of Jupiter, as perhaps having conditions that could support some sort of living thing.
8
People use yeast, one kind of unicellular organism, to make bread and beer. Others are
helpful because they eat harmful bacteria and are food for fish and other animals. At least one
kind of unicellular organism can cause illness in people. Amoebic dysentery, whose main
symptom is bloody diarrhea, is transmitted by water containing one type of amoeba. It is well
known as traveler's dysentery, or Montezuma's Revenge, particularly in Mexico. Liver infection
and abscesses can occur also. It can be treated with antibiotic drugs.
9
Unicellular organisms are all around us. They have lived on Earth for many millions of years
and have developed unique ways to survive. Although small, they are complex and beautiful.
The next time you look at pond water, just think what you might discover there!
10
Copyright © 2006 edHelper
1. What are unicellular organisms?
Animals with many cells
Plants with many cells
Not alive
Plants, animals, fungi, or bacteria
made of only one cell
2. What does unicellular mean?
Unicycle
One cell
Many cells
Multicellular
3. How long do scientists think unicellular
organisms have lived on Earth?
3.8 trillion years
3.8 million years
Millions of years
3.8 billion years
4. What is the advantage of having a
spherical shape?
Easier to move
Keeps it from drying out
More surface area for chemical
exchanges with the environment
Can get more food
5. What is the advantage of having a spiral
shape?
Can get more food
Easier to move
More surface area for chemical
exchanges with the environment
Keeps it from drying out
6. Where have extremophiles been found?
On the moon
On Mars and Europa
In Antarctica and the deep sea
On the sun
7. What is one kind of unicellular organism
that is helpful to people?
Paramecium
Euglena
Yeast
Amoeba
8. What does pseudopodia mean?
False name
Encyclopedia
Made-up name
False feet
Name _____________________________
Date ___________________
Unicellular Organisms
What are the differences between unicellular and multicellular organisms? Include as
many details as you can.
Unicellular Organisms
By Cindy Grigg
digest
adaptation
visible
ability
support
billion
sensitive
particularly
oblong
invisible
form
eventually
hair-like
drying
engulf
Directions: Fill in each blank with the word that best completes the reading comprehension.
You know that living things are made of cells. Some animals and
plants are made of only one cell. They are called unicellular. Unimeans one as a unicycle has only one wheel. Most of us don't think
about these unicellular creatures very much, but they are all around
us. Most are (1) _______________________ without a microscope,
but a few may be (2) _______________________ to the naked eye.
The main groups of unicellular organisms are bacteria, protozoa,
unicellular algae, and unicellular fungi or yeasts. Each species is
unique, and they are interesting to study because of their complex and beautiful patterns. Some
unicellular organisms are (3) _______________________ to light. They may move toward it
or away from it, and they have ingenious ways of moving around. They also respond to touch.
Some can live in very hostile environments.
Single-celled organisms have been on earth for perhaps 3.8
(4) _______________________ years, so they have had a long time in which to diversify.
Scientists believe they were the first life-forms on Earth. Although small, they are complex. They
have ancient and effective means of survival. The more that we learn about them, the more
amazing we find them to be.
Some of their survival mechanisms have to do with their shapes. They may be spheres,
oblong, or spiral. A spherical shape resists (5) _______________________ out, something
that would be fatal to a cell. An (6) _______________________ shape gives the cell more
surface area for chemical exchanges with its environment. A spiral shape makes it easier for the
organism to move.
Unicellular organisms have unique ways to move. Some, such as euglena, have tiny
(7) _______________________ fibers that are called flagella. These fibers thrash in the water
and drive the cell forward. The word flagellum means whip in Latin. Flagella (pronounced fla-jellah) is the plural (8) _______________________ . Some have groups or rows of tiny fibers that
move together like oars in a sort of rippling pattern. These are called cilia (pronounced silly-ah).
Cells with cilia move fast! A paramecium is one unicellular organism that moves with cilia.
Some unicellular organisms called amoebas are able to change their shapes. These "shapeshifters" can extend parts of themselves into what are called pseudopodia and then flow in the
direction in which they wish to go. Pseudopodia (pronounced sue-do-pode-ee-ah) means false
feet. If they find something to eat, they can (9) _______________________ , or surround, the
particle with their pseudopodia. Then they pull themselves around it to
(10) _______________________ it.
Just as the amoeba uses its pseudopodia both for movement and feeding, some unicellular
organisms with cilia also use the cilia to catch food. The stentor has cilia that beat rhythmically,
which draws food into its mouth. This is an (11) _______________________ that allows
stentors to spend most of their lives attached to a surface, saving their energy for catching food.
Some unicellular organisms live in extreme environments. Critters that like living in such
challenging places are called extremophiles. They have been found in such unfriendly habitats
as Antarctic ice and in very hot deep-sea vents. The (12) _______________________ of
organisms to adapt to extremely hot or cold environments gives scientists hope that signs of life
will (13) _______________________ be found on other planets. They have targeted Mars and
Europa, an icy moon of Jupiter, as perhaps having conditions that could
(14) _______________________ some sort of living thing.
People use yeast, one kind of unicellular organism, to make bread and beer. Others are
helpful because they eat harmful bacteria and are food for fish and other animals. At least one
kind of unicellular organism can cause illness in people. Amoebic dysentery, whose main
symptom is bloody diarrhea, is transmitted by water containing one type of amoeba. It is well
known as traveler's dysentery, or Montezuma's Revenge, (15) _______________________ in
Mexico. Liver infection and abscesses can occur also. It can be treated with antibiotic drugs.
Unicellular organisms are all around us. They have lived on Earth for many millions of years
and have developed unique ways to survive. Although small, they are complex and beautiful.
The next time you look at pond water, just think what you might discover there!
Copyright © 2006 edHelper
Name _____________________________
Date ___________________
Unicellular Organisms
1. What are unicellular organisms?
Plants with many cells
Animals with many cells
Plants, animals, fungi, or bacteria
made of only one cell
Not alive
2. What does unicellular mean?
One cell
Unicycle
Multicellular
Many cells
3. How long do scientists think unicellular
organisms have lived on Earth?
3.8 billion years
3.8 million years
3.8 trillion years
Millions of years
4. What is the advantage of having a
spherical shape?
Easier to move
Can get more food
Keeps it from drying out
More surface area for chemical
exchanges with the environment
5. What is the advantage of having a spiral
shape?
Easier to move
Keeps it from drying out
More surface area for chemical
exchanges with the environment
Can get more food
6. Where have extremophiles been found?
In Antarctica and the deep sea
On the sun
On the moon
On Mars and Europa
7. What is one kind of unicellular organism
that is helpful to people?
Paramecium
Euglena
Yeast
Amoeba
8. What does pseudopodia mean?
Encyclopedia
Made-up name
False name
False feet
Date ___________________
Name _____________________________
(Key 1 - Answer ID # 1070361)
Find each of the following words.
DEEP-SEA
SURVIVAL
VISIBLE
ENGULF
SENSITIVE
HOSTILE
EXTREMELY
NAKED
FORM
HARMFUL
ABILITY
DIVERSIFY
INVISIBLE
OBLONG
INGENIOUS
CHEMICAL
I L B M N P R S O I T B X G N O L B O O A F S U I E
B S I L W S L F N A K E D H X H N R S E I Y L A L V
V - V N T A O I E S C I F R E N P A S I E A N V A T
F O R M H U F X Y F I S R E V I D - I O A N S V O D
N S E N S I T I V E R R A S I I P I V T I E X S T L
F I Y T I L I B A S H E S H S E I H I N L - R E F R
E L E R K E H M U H K U H E E N H E T E R S E E L L
I S U A N E E E M I E B X D G A S I I L I V I E U N
M B E G D I N O B L A N G E S O I V S B N L I T G V
S R L L N E A S I S N S N T I C E B N I V U D H N N
B I S U B A E T G K N I I H N I E T E S I X V U E E
R N O O O E S P M V O L A U I S A G S I S E R L X R
Y L N L S O S D - U E R E H A M F U L V I E L H T V
E V V B H U E I S S M L H U V I I V U S B B E I R I
T E I
I D B R T V F A S U I O N E G N I L I I B E T
R L M S S U S V U N L E L L U E E M F C E I C U M I
I S E I A R K L I I I Y F E S R E V I D A I I L E F
L B A V M L R Y S V R E A E F N C H E M I C A L L X
V E S R M E N S A H A C U E X T E M E L Y I B M Y L
E T M E O I R E U N B L S T L V H V N E C C I V G L
N I E H A M V N T E A L I V E V C I N U I M Y I V G
Unicellular Organisms - Answer Key
1
2
3
4
5
6
7
8
Plants, animals, fungi, or bacteria made of only one cell
One cell
3.8 billion years
Keeps it from drying out
Easier to move
In Antarctica and the deep sea
Yeast
False feet
Unicellular Organisms
By Cindy Grigg
Answer Key
You know that living things are made of cells. Some animals and plants are made of only one
cell. They are called unicellular. Uni- means one as a unicycle has only one wheel. Most of us
don't think about these unicellular creatures very much, but they are all around us. Most are
(1) invisible without a microscope, but a few may be (2) visible to the naked eye.
The main groups of unicellular organisms are bacteria, protozoa, unicellular algae, and
unicellular fungi or yeasts. Each species is unique, and they are interesting to study because of
their complex and beautiful patterns. Some unicellular organisms are (3) sensitive to light. They
may move toward it or away from it, and they have ingenious ways of moving around. They also
respond to touch. Some can live in very hostile environments.
Single-celled organisms have been on earth for perhaps 3.8 (4) billion years, so they have
had a long time in which to diversify. Scientists believe they were the first life-forms on Earth.
Although small, they are complex. They have ancient and effective means of survival. The more
that we learn about them, the more amazing we find them to be.
Some of their survival mechanisms have to do with their shapes. They may be spheres,
oblong, or spiral. A spherical shape resists (5) drying out, something that would be fatal to a
cell. An (6) oblong shape gives the cell more surface area for chemical exchanges with its
environment. A spiral shape makes it easier for the organism to move.
Unicellular organisms have unique ways to move. Some, such as euglena, have tiny
(7) hair-like fibers that are called flagella. These fibers thrash in the water and drive the cell
forward. The word flagellum means whip in Latin. Flagella (pronounced fla-jell-ah) is the plural
(8) form . Some have groups or rows of tiny fibers that move together like oars in a sort of
rippling pattern. These are called cilia (pronounced silly-ah). Cells with cilia move fast! A
paramecium is one unicellular organism that moves with cilia.
Some unicellular organisms called amoebas are able to change their shapes. These "shapeshifters" can extend parts of themselves into what are called pseudopodia and then flow in the
direction in which they wish to go. Pseudopodia (pronounced sue-do-pode-ee-ah) means false
feet. If they find something to eat, they can (9) engulf , or surround, the particle with their
pseudopodia. Then they pull themselves around it to (10) digest it.
Just as the amoeba uses its pseudopodia both for movement and feeding, some unicellular
organisms with cilia also use the cilia to catch food. The stentor has cilia that beat rhythmically,
which draws food into its mouth. This is an (11) adaptation that allows stentors to spend most
of their lives attached to a surface, saving their energy for catching food.
Some unicellular organisms live in extreme environments. Critters that like living in such
challenging places are called extremophiles. They have been found in such unfriendly habitats
as Antarctic ice and in very hot deep-sea vents. The (12) ability of organisms to adapt to
extremely hot or cold environments gives scientists hope that signs of life will (13) eventually
be found on other planets. They have targeted Mars and Europa, an icy moon of Jupiter, as
perhaps having conditions that could (14) support some sort of living thing.
People use yeast, one kind of unicellular organism, to make bread and beer. Others are
helpful because they eat harmful bacteria and are food for fish and other animals. At least one
kind of unicellular organism can cause illness in people. Amoebic dysentery, whose main
symptom is bloody diarrhea, is transmitted by water containing one type of amoeba. It is well
known as traveler's dysentery, or Montezuma's Revenge, (15) particularly in Mexico. Liver
infection and abscesses can occur also. It can be treated with antibiotic drugs.
Unicellular organisms are all around us. They have lived on Earth for many millions of years
and have developed unique ways to survive. Although small, they are complex and beautiful.
The next time you look at pond water, just think what you might discover there!
Answers to Reading Comprehension Questions
1
2
3
4
5
6
7
8
Plants, animals, fungi, or bacteria made of only one cell
One cell
3.8 billion years
Keeps it from drying out
Easier to move
In Antarctica and the deep sea
Yeast
False feet
Answer Key 1070361
Key # 1
DEEP-SEA
SENSITIVE
FORM
INVISIBLE
SURVIVAL
HOSTILE
HARMFUL
OBLONG
VISIBLE
EXTREMELY
ABILITY
INGENIOUS
ENGULF
NAKED
DIVERSIFY
CHEMICAL
G N O L B O
N A K E D
A
E
S
F O R M
Y F I S R E V I D -
S E N S I T I V E
P
Y T I L I B A
E I
E N
E
L
I
I
S
O
S O
U
H U
S
R
E
L
D G
L I
U
E
B N
G
I V
N
S I
E
I S
X
V I
T
B
R
L
E
E
M
N
T
H
A
R
M
F
V U
L I
F
E
V
C H E M I C A L L
A
Y
L