Lesson 3 | What are viruses?
Student Labs and Activities / Page / Appropriate For:Launch Lab / 46 / all students
Content Vocabulary / 47 / all students
Lesson Outline / 48 / all students
MiniLab / 50 / all students
Content Practice A / 51 /
Content Practice B / 52 /
School to Home / 53 / all students
Key Concept Builders / 54 /
Enrichment / 58 / all students
Challenge / 59 /
Lab A / 62 /
Lab B / 65 /
Lab C / 68 /
Chapter Key Concepts Builder / 69 /
Assessment
Lesson Quiz A / 60 /
Lesson Quiz B / 61 /
Chapter Test A / 70 /
Chapter Test B / 73 /
Chapter Test C / 76 /
/ Approaching Level / / On Level / / Beyond Level / / English-Language Learner
Teacher evaluation will determine which activities to use or modify to meet anystudent’s proficiency level.
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LESSON 3: 10 minutes
How quickly do viruses replicate?
One characteristic that viruses share is the ability to produce many new viruses from just
one virus. In this lab, you can use grains of rice to model virus replication. Each grain of
rice represents one virus.
Procedure
1.Read and complete a lab safety form.
2.Estimate the number of grains of
rice in the fishbowl and record this
number for the first generation in the
table below.
3.One student will add the contents
of his or her cup to the fishbowl.
Estimate how many viruses are now in
the fishbowl and record your estimate
for the second generation.
4.The rest of the class will add the
contents of their cups to the fishbowl.
Estimate the number of viruses and
record that number of viruses for the
third generation.
Data and Observations
Generation / First / Second / ThirdNumber of
“viruses”
Think About This
1.Recall that bacteria double every generation. How does the number of viruses
produced in each generation compare with the number of bacteria produced in each
generation?
2.Key Concept How could the rate at which viruses are produced affect human
health?
46Bacteria and Viruses
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LESSON 3
What are viruses?
Directions: Answer each question on the lines provided. You must include the terms below in your answer.
antibodyimmunitymutationvaccinevirus
1.What are viruses?
2.How do antibodies interact with viruses?
3.What is a mutation?
4.What does it mean if a person has developed an immunity against a specific virus?
5.How does a vaccine protect a person from viral disease?
Bacteria and Viruses47
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LESSON 3
What are viruses?
A.Characteristics of Viruses
1.A(n) is a strand of DNA or RNA surrounded by a layer
of protein that can infect and replicate in a host cell.
2.A virus does not have a(n) , any other organelles, or
a cell membrane.
3.Scientists do not consider viruses to be because they do
not have all the characteristics of a living organism.
4.Viruses must use to carry on the processes that we
usually associate with a living cell.
a.The living cell that a virus infects is called a(n) cell.
b.After a virus attaches to the host cell, its DNA or
enters the host cell.
c.When a virus enters a cell, it can be for years before
taking over the cell.
d.After a virus replicates in the host cell, it the host
cell. Copies of the virus are then released into the host organism, where they can
other cells.
5.As viruses replicate, their DNA or RNA frequently ,
or changes.
a.As viruses change, they can produce new ways to
to host cells.
b.These changes happen so rapidly that it can be difficult to cure or prevent viral
before the virus mutates again.
B.Viral Diseases
1.Viruses cause many human , such as chicken pox,
influenza, HIV, and the common cold. Viruses can also affect other animals
and .
2.Viruses such as influenza cause symptoms soon after .
viruses such as HIV might not cause symptoms
right away.
48Bacteria and Viruses
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Lesson Outline continued
C.Treating and Preventing Viral Diseases
1.Viral diseases can be difficult to treat because viruses are
constantly .
2.Antibiotics work only against , not viruses.
3.One of the best ways to prevent a viral infection is to limit
with an infected organism.
4. occurs when a person is infected by a virus and then
becomes immune to it.
a.When a virus infects a person, the body begins to make special proteins
called.
b.An antibody is a protein that prevents a(n) in the
body.
5. develops when a mother passes antibodies to her
unborn baby.
6.A(n) is a mixture containing material from one
or more deactivated pathogens, such as viruses. It triggers the production
of .
D.Research with Viruses
1.Scientists are researching new ways to treat and viral
diseases in humans, animals, and plants.
2.Scientists are studying the link between viruses and .
3.Viruses are being tested as treatments for genetic disorders and cancer
using .
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LESSON 3: 20 minutes
How do antibodies work?
When a virus infects a cell, it binds to a part of that cell called a receptor. The virus and the
receptor fit together like puzzle pieces.
Procedure
1.Read and complete a lab safety form.
2.Cut out two virus shapes and two
cell shapes.
3.Using one virus shape and one cell
shape, note how the virus fits against
the receptor on the cell. Tape the virus
and the cell together.
4.Cut out one antibody shape. Note
how the virus shapes and the antibody
shapes attach, and tape them together.
5.Try to attach the virus shapes and the
antibody shapes that you just joined to
the cell receptor.
Data and Observations
Analyze and Conclude
1.Observe whether the virus or the joined virus and antibody were better able to attach
to the cell.
2.Key Concept Explain how producing more antibodies would be beneficial
during a viral infection.
50Bacteria and Viruses
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LESSON 3
What are viruses?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Each term is
used only once.
acquiredantibodybeneficialcellsdiseases
hostlatentmembranemutatesprotein
replicateshapesvaccine
1.A virus is a strand of DNA or RNA surrounded by a layer of
that can infect and replicate in a host cell.
2.A virus can infect and cause illness.
3.A virus does not have a nucleus or a cell .
4.Viruses can have different , such as crystals and cylinders.
5.The living cell that a virus infects is called a(n) cell.
6.When a virus enters a cell, it can be active or .
7.Viruses must take control of a specific kind of cell to .
8.Viruses can adjust to changes in their host cell because their DNA or RNA frequently
.
9.Viruses cause , such as chicken pox, influenza, HIV,
influenza, and rabies.
10.A(n) is a protein that prevents an infection in your body.
11.You develop immunity when you have a viral disease.
12.A(n) is a mixture containing material from one or more
deactivated pathogens, such as viruses.
13.Scientists have developed uses for viruses in treating
genetic disorders and cancer using gene therapy.
Bacteria and Viruses51
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LESSON 3
What are viruses?
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.A virus is a strand of DNA or RNA surrounded by a layer of cytoplasm that can
infect and replicate in a host cell.
2.Viruses cause diseases by infecting specific kinds of cells.
3.Viruses have a nucleus.
4.Viruses have a cell membrane.
5.Crystal, cylinder, and sphere are three examples of virus shapes.
6.When a virus enters a host cell, it can be active or latent.
7.Viruses replicate by taking control of a specific kind of cell.
8.Because the DNA or RNA in viruses frequently reproduces, viruses can adjust
to changes in their host cell.
9.Chicken pox, influenza, HIV, and rabies are examples of diseases caused by
viruses.
10.An antibiotic is a protein that prevents a virus from causing a disease if it
enters your body.
11.When you had a disease caused by a virus and recovered, you developed active
immunity.
12.Activated viruses are used to make vaccines.
13.Scientists are researching ways to use viruses for treating genetic disorders
and cancer.
52Bacteria and Viruses
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LESSON 3
What are viruses?
Directions: Use your textbook to answer each question or respond to each statement.
1.A strand of DNA or RNA surrounded by a layer of protein that can infect
a host cell is a virus.
Do viruses reproduce? Explain your answer.
2.Viruses use living cells to carry out the functions we associate with living
organisms.
What happens to a living cell when a virus enters it?
3.Viruses infect living cells in plants, animals, and people.
Why can living organisms infected with a virus still appear to be healthy?
4.A mixture that contains material from one or more deactivated viral
pathogens is one type of vaccine.
Can people get the flu from a flu vaccine? Explain your answer.
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LESSON 3
What are viruses?
Key Concept What are viruses?
Directions: Put a check mark on the line before each characteristic that applies to a virus.
1.has a strand of DNA or RNA
2.is surrounded by a layer of protein
3.infects cells
4.has a nucleus
5.has a cell membrane
6.has organelles
7.is between 20 and 100 times smaller than most bacteria
8responds to stimuli
9.uses energy
10.reproduces by fission
11.grows
12.can be shaped like a crystal
Directions: Answer the question on the lines provided.
13.Why don’t scientists consider viruses to be alive?
54Bacteria and Viruses
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LESSON 3
What are viruses?
Key Concept What are viruses?
Directions: Answer each question or respond to each statement in the space provided.
Virus Replication1.Draw and label the first step of a virus
infecting a cell. / 2.Describe what is happening in your drawing.
3.What are two different things that can
happen next? / 4.What happens if the virus is latent?
5.What happens if the virus is active? / 6.What happens next?
7.Explain why a virus cannot infect every cell.
8.Explain how viruses can still attach to host cells even if the host cells change over time.
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LESSON 3
What are viruses?
Key Concept How do viruses affect human health?
Directions: Answer each question or respond to each statement in the space provided.
1.Explain what causes the symptoms of viral diseases.
2.Which cells of the body do influenza viruses infect first? What happens after that?
3.Why might human immunodeficiency viruses (HIV) not cause symptoms right away?
Which cells do they infect?
4.What is an antiviral medicine, and what are its limitations?
5.What are two ways to avoid getting a viral disease, such as the common cold?
56Bacteria and Viruses
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LESSON 3
What are viruses?
Key Concept How do viruses affect human health?
Directions: Answer each question on the lines provided.
Viruses and HealthQuestion / Answer
1.How does a person
develop acquired
immunity to a disease?
2.Why does an antibody
only work for a specific
virus?
3.How does a vaccine
trigger the body to
produce antibodies?
4.Why are the viruses in
a vaccine deactivated?
5.What beneficial uses
have scientists
developed for viruses?
6.Which characteristic of
viruses makes them
useful in gene therapy
research?
Bacteria and Viruses57
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LESSON 3
A Virus That Changed History
Around 1520, Hernán Cortés led some
500 Spanish conquistadors into the mighty
Aztec Empire, which ranged across Mexico
and Central America. One of his soldiers
had smallpox, a highly contagious virus.
The disease spread rapidly, killing an
estimated 3 million Aztecs. Cortés’s small
group was able to conquer the empire, not
through weapons, but through disease.
No Immunity
For centuries, epidemics of smallpox
had routinely swept through Europe. Those
who survived carried a lifelong immunity
to the virus. But smallpox had never
touched the New World until the first
Europeans landed on its shores. Thus, the
Native American population had no
immunity to the disease, so millions died.
Near the time of the Aztec epidemic,
smallpox was killing half the population
of Hispaniola, an island in the West Indies.
It helped bring about the fall of the Inca
Empire in the 1530s. In the 1700s, a
smallpox epidemic raged through what
is now the United States. It wiped out
entires Native American tribes and
weakened many others. Historians say the
epidemic helped open the way for
European settlers to move west.
Smallpox Today
A safe vaccine for smallpox was
developed in 1796. Today, smallpox
no longer kills millions of people. No
outbreaks have been reported in the
United States since 1949. Worldwide, the
last-known case of smallpox occurred in
1977. Vaccinations for smallpox are no
longer given to children.
Health officials still keep a close eye on
smallpox, however. The virus is kept secure
in two labs in the United States and Russia.
Vaccines for the virus are stored as well. The
Centers for Disease Control and Prevention
(CDC), the U.S. agency that monitors
public health, still classifies smallpox as a
Category A agent, meaning the virus has
great potential to cause harm. According to
the CDC, even one case of smallpox would
be considered a public emergency.
Applying Critical-Thinking Skills
Directions: Answer each question.
1.Judge The smallpox virus is extremely dangerous. What scientific benefit might
storing the virus provide us with rather than destroying it?
2.Predict How might history be different if smallpox had been common in the New
World and not in Europe?
58Bacteria and Viruses
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LESSON 3
Relationships in Communities
Viruses cannot replicate without a host cell. Write a skit about a virus that is searching
for a host cell. The host cell is within an organism that has acquired immunity against the
virus. Your skit should include dialogue between the virus and the antibodies in the
organism. The virus should describe itself in a brief introduction. It should also state its
purpose. The antibodies should counter by describing how they will ruin the virus’s plans.
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LESSON 3
What are viruses?
Multiple Choice
Directions: On the line before each statement, write the letter of the correct answer.
1. is the process that viruses use to make copies of themselves.
A.Fission
B.Replication
C.Conjugation
2.After a virus becomes active, it
A.replicates and becomes a host cell.
B.replicates and destroys its host cell.
C.replicates and produces new host cells.
Matching
Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term is
used only once.
3.strand of DNA or RNA surrounded by protein
that can infect and replicate in a host cell
4.protein that attaches to a pathogen and makes it
useless
5.drug used to treat viral infections
6.mixture of deactivated pathogens that can
prevent infection
7.inserting genetic information into cells as a way
of treating genetic disorders
A.antibody
B.antiviral medicine
C.gene therapy
D.vaccine
E.virus
60Bacteria and Viruses
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LESSON 3
What are viruses?
Completion
Directions: On each line, write the term that correctly completes each sentence.
1.A(n) includes a strand of DNA or RNA surrounded by a
layer of protein that can infect and replicate in a host cell.
2.When a virus infects someone, the body makes that
prevent the virus from attaching to cells.
3.Drugs that are used to treat or prevent viral infections are
medicines.
4.A mixture of deactivated pathogens that can prevent infection is
a(n) .
5.Inserting genetic information into cells to treat genetic disorders is
called .
Short Answer
Directions: Respond to each statement on the lines provided.
6.Compare and contrast active and latent viruses.
7.Describe viral replication.
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30 minutes
Bacterial Growth and Disinfectants
Recall that pathogens such as bacteria and viruses surround you. When studying pathogens,
scientists often use agar plates to grow bacteria and other colonies. An agar plate is a Petri
dish containing agar, a gel made from seaweed, and nutrients needed for bacteria to grow.
When bacteria are transferred to an agar plate, they reproduce. After a few days, you can see
colonies of bacteria. Disinfectants are chemicals that deactivate or kill pathogens such as
bacteria. In this lab, you will test how hand sanitizer, a common disinfectant, affects the
growth of bacteria on agar plates.
Ask a Question
What effect does hand sanitizer have on bacterial growth?
Materials
agar platescotton swabscellophane tape
permanent markerhand sanitizer
Safety
Make Observations
1.Read and complete a lab safety form.
2.Set two agar plates on your desk or work area. Turn your agar plates upside down
without opening them.