Lesson 1 | What are bacteria?
Student Labs and Activities
Page
Appropriate For:
Launch Lab
8
all students
Content Vocabulary
9
all students
Lesson Outline
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all students
MiniLab
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all students
Content Practice A
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Content Practice B
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Math Skills
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all students
School to Home
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all students
Key Concept Builders
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Enrichment
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Challenge
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all students
Assessment
Lesson Quiz A
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Lesson Quiz B
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Approaching Level
On Level
Beyond Level
Teacher evaluation will determine which activities to use or modify to meet any
Bacteria and Viruses
English-Language Learner
student’s proficiency level.
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Launch Lab
Class
LESSON 1: 10 minutes
How small are bacteria?
Bacteria are tiny cells that can be difficult to see, even with a microscope. You might be
surprised to learn that bacteria are found all around you, including in the air, on your skin,
and in your body. One way to understand how small bacteria are is to model their size.
Procedure
1. Read and complete a lab safety form.
2. Examine the size of a baseball and a
3. As a class, count how many baseballs it
takes to fill the bucket.
2.5-gal. bucket. Estimate how many
baseballs you think would fit inside the
bucket.
Data and Observations
Think About This
1. How much larger is the bucket than a baseball?
2. If your skin cells were the size of the bucket and bacteria were the size of the baseballs,
how many bacterial cells would fit on a skin cell?
3.
Key Concept Why do you think you cannot see bacteria on your skin or on
your desk?
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Content Vocabulary
LESSON 1
What are bacteria?
Directions: On each line, write the term from the word bank that correctly replaces the underlined words in
each sentence.
bacterium
conjugation
endospore
fission
flagellum
1. Scientists have studied a(n) microscopic prokaryote; many
of these live in and on your body.
2. When environmental conditions are unfavorable for
growth and development, a bacterium can form a(n) thick
internal wall around its chromosome and part of the
cytoplasm.
3. The combining of genetic material of bacteria results in
new genes.
4. Bacteria can use a(n) whiplike structure to move.
5. Bacteria reproduce through cell division that results in
genetically identical cells.
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LESSON 1
Lesson Outline
What are bacteria?
A. Characteristics of Bacteria
1.
are unicellular organisms that do not have a nucleus
or other membrane-bound organelles.
2.
are microscopic prokaryotes.
3. There are two types of prokaryotes—bacteria and
.
4. A typical bacterium consists of DNA and
surrounded
by a cell membrane and a cell wall.
a. Bacterial cytoplasm also contains
.
b. Bacterial DNA occurs in one coiled, circular
.
A bacterium might also have smaller, circular
are separate from its other DNA.
that
5. Many bacteria have capsules with hairlike structures called
that help the bacteria stick to surfaces.
6. Bacteria are much
than plant or animal cells.
7. Bacteria generally have one of three basic shapes—sphere, rod,
or
.
8. Some bacteria take in food and break it down and
obtain
.
The food can come from dead organisms or
hosts.
9. Other bacteria make their food using energy from
or
chemical reactions.
10.
bacteria can survive without oxygen.
bacteria need oxygen, as humans do.
11. Many bacteria have long whiplike structures called
that
they use for movement.
12. Bacteria reproduce asexually by
division forms two genetically
10
. This type of cell
cells.
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Lesson Outline continued
13. During
, two bacteria of the same species attach to each
other and combine their genetic material.
a.
is transferred between bacteria during conjugation.
b. Conjugation results in new combinations of genes and increases
genetic
.
B. Endospores
1. A(n)
forms when a bacterium builds a thick inner wall
around its chromosome and part of the cytoplasm.
2. An endospore can protect a bacterium from intense heat, cold, or
. It can remain
for months
or even centuries.
C. Archaea
1. Like a bacterium, a(n)
has a cell wall but no nucleus
or membrane-bound organelles.
2. The ribosomes of archaea more closely resemble the ribosomes of
than those of bacteria.
3. Archaea often live in
environments, such as hot springs
and salt lakes.
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MiniLab
Class
LESSON 1: 15 minutes
How does a slime layer work?
Bacteria have a gelatinlike, protective coating called a slime layer on the outside of their cell
walls. A slime layer can help a bacterium attach to surfaces or reduce water loss.
Procedure
1. Read and complete a lab safety form.
2. Cut two 2-cm-wide strips from the long
side of a synthetic kitchen sponge.
4. Completely coat one strip with hairstyling gel to simulate a slime layer.
5. Place both strips on a plate and let
3. Soak both strips in water. Remove
them sit overnight.
them from the water and squeeze out
the excess water. Both strips should be
damp.
Data and Observations
Analyze and Conclude
1. Describe the appearance of the two strips. How do they differ?
2.
Key Concept Explain how a slime layer might be beneficial to a bacterium when
moving or finding food.
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LESSON 1
Content Practice A
What are bacteria?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Each term is
used only once.
archaea
bacteria
conjugation
cytoplasm
endospore
fission
flagella
food
plasmid
reproduction
shapes
identical
1. Prokaryotes that live in almost every habitat on Earth
are
.
2. Prokaryotes that live in extreme environments are
3. A typical bacterium has
.
and DNA surrounded by a cell
membrane and a cell wall.
4. A(n)
is a small circular piece of DNA.
5. Bacteria generally have one of three basic
, which
determines how they are named.
6. Different bacteria have different methods for movement and for
obtaining
.
7. Many bacteria move by using long whiplike structures
called
.
8. Bacteria reproduce asexually by
, which produces two
genetically
cells.
9. During
, two bacteria of the same species attach to each
other and combine their genetic material.
10. Conjugation increases genetic diversity, but it is not considered to
be
11. A(n)
.
forms when a bacterium builds a thick internal
wall around its chromosome.
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LESSON 1
Content Practice B
What are bacteria?
Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the
statement is false, change the underlined word(s) to make it true. Write your changes on the lines provided.
1. Unicellular prokaryotes called bacteria live almost everywhere on Earth.
2. Extreme environments are habitats for unicellular prokaryotes called archaea.
3. A nucleus, DNA, a cell membrane, and a cell wall make up a typical bacterium.
4. A small circular piece of cytoplasm is a plasmid.
5. Bacteria generally have one of two basic shapes that determine how they are
named.
6. Ways to obtain food and to move differ among bacteria types.
7. Whiplike structures called flagella are used by many bacteria to move.
8. Conjugation is a way bacteria reproduce asexually.
9. Fission is cell division that forms two genetically different cells.
10. Two bacteria of the same species attach to each other and combine their
genetic material during fission.
11. Conjugation is not considered to be reproduction, although it does increase
genetic diversity.
12. Some bacteria can form an endospore, which is a wall around the chromosome
and part of the cytoplasm.
13. Endospores protect bacteria from unfavorable conditions by allowing them to
remain dormant.
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Math Skills
LESSON 1
Use a Formula
Bacteria reproduce asexually through fission. One bacterium divides and results in
2 genetically identical cells. As the fission continues, the 2 cells produce 4 cells, the 4 cells
produce 8 cells, and so on. The number of resulting cells doubles each time.
The number of bacteria produced after each round of fission can be shown by the equation
below, where n = final number of bacteria, x = initial number of bacteria, and f = the number
of rounds of cell division.
n = x × 2f
This equation includes the exponential expression 2f. The base is 2 and the exponent f is
the number of times fission occurs.
If 20 bacteria undergo fission 4 times, how many bacteria will result?
Step 1
Identify the variables.
x = 20
f=4
Step 2
Substitute the known values to solve the equation.
n = 20 × 24
n = 20 × (2 × 2 × 2 × 2)
n = 320
After four rounds of division, there will be 320 bacteria.
Practice
1. If 15 bacteria undergo fission 4 times,
how many bacteria will result?
3. If 50 bacteria undergo fission 8 times,
how many bacteria will result?
Hint: 28 = 256.
4. If 120 bacteria undergo fission
2. If 100 bacteria undergo fission 5 times,
how many bacteria will result?
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16 times, how many bacteria will
result? Hint: 216 = 65,536.
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School to Home
Class
LESSON 1
What are bacteria?
Directions: Use your textbook to answer each question.
1. Bacteria are microscopic prokaryotes that live almost everywhere on Earth.
What are prokaryotes?
2. Bacteria are extremely diverse organisms that have three basic shapes.
What are the three basic shapes of bacteria?
3. Bacteria grow in nearly every environment. Because the environments are
so different, bacteria have different ways to obtain food.
In which three ways do bacteria obtain food?
4. When a bacterium builds a large external wall around its chromosome and
part of its cytoplasm, an endospore is formed.
In which types of conditions would an endospore be present?
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LESSON 1
Key Concept Builder
What are bacteria?
Key Concept What are bacteria?
Directions: Complete the Venn diagram below by writing features of bacteria on the left and archaea on the
right. Write what they have in common in the center.
1. Bacteria
2. Both
3. Archaea
Directions: Answer each question or respond to each statement on the lines provided.
4. Describe the DNA in bacteria.
5. Explain how a capsule helps some bacteria survive.
6. What are pili, and what function do they serve in some bacteria?
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Key Concept Builder
LESSON 1
What are bacteria?
Key Concept What are bacteria?
Directions: Complete this table by drawing the three basic shapes of bacteria.
1. Sphere-Shaped
2. Rod-Shaped
3. Spiral-Shaped
Directions: Answer each question on the lines provided.
4. How does the size of a typical bacterium compare to the size of a typical eukaryotic cell?
5. What are two sources of nutrients for bacteria that take in food?
6. How do bacteria that do not take in food get energy to survive?
7. What is the difference between anaerobic bacteria and aerobic bacteria?
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Key Concept Builder
Class
LESSON 1
What are bacteria?
Key Concept What are bacteria?
Directions: Answer each question or respond to each statement on the lines provided.
Question
Answer
1. Describe three ways
that some bacteria
move around to find
resources.
2. What are some
environmental
conditions that make
it difficult for bacteria
to survive?
3. What do some
bacteria do to survive
in unfavorable
environmental
conditions?
4. What happens to the
parts of the bacterium
that are not protected
by an endospore?
5. How does an
endospore allow a
bacterium to survive?
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Key Concept Builder
LESSON 1
What are bacteria?
Key Concept What are bacteria?
Directions: On the line before each description, write F if it applies to fission or C if it applies to conjugation.
1. how bacteria reproduce
2. asexual reproduction
3. not considered reproduction
4. forms two genetically identical cells
5. increases genetic variation
6. forms cells identical to parent cell
7. forms two new cells
8. does not form new organisms
9. also called cell division
10. two bacteria of the same species attach to each other
11. two bacteria of the same species combine genetic material
12. involves the transfer of DNA
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Enrichment
LESSON 1
Extremophiles
Certain prokaryotes are found in some of
the hottest, deepest, and coldest places on
Earth. These prokaryotes are extremophiles,
meaning they can live in extreme
environments. They include bacteria and
archaea. Their existence raises interesting
questions about the possibility of life in
other extreme places, such as planets and
moons in the solar system.
the base of the food chain in the
hydrothermal-vent community.
Could extremophiles thrive on the
ocean floors of Europa? Scientists are
hoping that question might be answered
in the near future. Currently, NASA is
planning its next major mission within the
solar system. There is a good chance the
mission will include a thorough study of
Europa and its icy sea.
Extreme Environments
Searching for Extremophiles
The moons of Jupiter and Saturn are
cold, dim, and apparently lifeless. But,
environmental conditions on some of
these moons may be conducive to life. For
example, evidence indicates that Europa,
one of Jupiter’s moons, is covered by an
icy crust that floats on a liquid ocean.
Scientists theorize that hydrothermal vents
might exist on Europa’s ocean floors. A
hydrothermal vent is a crack in the ocean
floor through which water emerges. The
water, heated by interior processes, is
extremely hot.
Since the 1970s, scientists have known
that hydrothermal vents exist on Earth’s
ocean floor. These vents teem with life,
including extremophiles. In fact, the
microbes might be the most important
members of the hydrothermal ecosystem.
The microbes are producers. They use
chemicals to make their food and form
In the meantime, scientists are learning
more about the possibilities of extraterrestrial
life by studying extremophiles on Earth. In
2008, an international group of scientists
went to Lake Untersee in Antarctica to
search for extremophiles. Lake Untersee is
cold and highly alkaline. Its pH level is
similar to the pH of bleach. In addition,
sediments in the lake produce a lot of
methane. These conditions—the cold, the
pH level, and the methane—mimic the
extreme conditions found on some of the
moons of Saturn and Jupiter.
Scientists are still studying the
specimens gathered from Lake Untersee.
If extremophiles are found in the lake, it
will lend support to the theory that the
hardy microbes can thrive on distant
planets and moons.
Diverse Ecosystem
Applying Critical-Thinking Skills
Directions: Answer each question.
1. Differentiate How does the source of energy for producers in hydrothermal vents differ
from that of green plants?
2. Consider Do you think the presence of extremophiles on Earth indicates that life
might exist on other planets and moons? Why?
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Challenge
LESSON 1
Bacteria Shapes and Sizes
Bacteria have different shapes and sizes. Some also have special structures that help them
move. These tiny organisms are too small to be seen with the unaided eye. But you can
view bacteria with a microscope. You can use a prepared slide or prepare a wet-mount slide
by following the steps below.
Make a Slide
1. Place a teaspoon of plain yogurt with active cultures on a small plate. Add several drops
of water to the yogurt and stir.
2. Use a dropper to put 1 drop of the yogurt-water mixture on a clean glass slide.
3. Hold a coverslip by the edges and carefully lower it onto the slide.
4. Place the slide on the stage of a microscope. Use the stage clips to secure the slide.
5. Focus with the low-power objective lens first. Then view the specimen through the
high-power objective lens.
6. Sketch the bacteria in the space below. Include captions that compare the shapes of the
bacteria you observed.
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Lesson Quiz A
Class
LESSON 1
What are bacteria?
Multiple Choice
Directions: On the line before each question, write the letter of the correct answer.
1. How do bacteria reproduce?
A. by fission
B. by endospores
C. by conjugation
2. Which word describes bacteria that do not need oxygen?
A. aerobic
B. anaerobic
C. asymmetric
Matching
Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term is
used only once.
Matching Set 1
3. hairlike structures that help cells stick to things
4. whiplike structures that help with cell movement
5. microscopic prokaryotes that are commonly
shaped like spheres, rods, or spirals
A. bacteria
B. pili
C. aerobic
D. flagella
6. describes bacteria that need oxygen
Matching Set 2
7. a way in which bacteria transfer genetic material
E. extremophiles
8. one-celled organism that lacks a nucleus
F. conjugation
9. archaea that live in harsh environments
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G. prokaryote
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Lesson Quiz B
LESSON 1
What are bacteria?
Completion
Directions: On each line, write the term that correctly completes each sentence.
1. Hairlike structures that help bacteria stick to things are
called
.
2. Whiplike structures that help bacteria move are called
3.
.
are microscopic prokaryotes that are commonly shaped
like spheres, rods, or spirals.
4.
is a way in which bacteria exchange genetic material.
5.
is the process by which bacteria produce genetically
identical offspring.
6. A one-celled organism that lacks a nucleus is a(n)
.
Short Answer
Directions: Respond to each statement on the lines provided.
7. Recall the ways in which archaea are different from bacteria.
8. Contrast aerobic and anaerobic bacteria.
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