SECTION 1: GENERATE AN ARGUMENT
CHARACTERISTICS OF VIRUSES
(CHARACTERISTICS OF LIFE)
10
A
virus is a tiny bundle of genetic material—either DNA or RNA—carried in a protein
shell called a capsid. Some viruses have an additional layer around this coat called an
envelope. The envelope is made of a lipid. Three examples of viruses can be seen in
Figure 10.1.
Figure 10.1. An Adenovirus, a Bacteriophage, and the Influenza Virus (These viruses are
between 45 and 200 nanometers.)
[A nanometer is 1/1,000,000,000 of a meter].
When a virus enters a cell, the information carried in a virus’s genetic material enables the virus
to force the infected cell to make more copies of the virus. The poliovirus, for example, can make over
one million copies of itself inside a single human intestinal cell. A virus is usually very, very small
compared to the size of the cell it infects.
Viruses can infect the cells of plants, animals, or even bacteria. Moreover, within an individual
species, there may be one hundred or more different types of viruses, which can infect that specific
species alone. There are viruses that infect only humans (for example, smallpox), viruses that infect
humans and one or two additional kinds of animals (for example, influenza), viruses that infect
only a certain kind of plant (for example, the tobacco mosaic virus), and some viruses infect only a
particular species of bacteria (for example, the bacteriophage which infects E. coli).
These unique traits of viruses have made many scientists wonder: Should a virus be classified
as a living thing?
With your group, develop a claim that best answers this research question. Once your group has
developed your claim, prepare a whiteboard that you can use to share and justify your ideas. Your
whiteboard should include all the information shown in Figure 10.2 on page 124.
SCIENTIFIC ARGUMENTATION IN BIOLOGY: 30 CLASSROOM ACTIVITIES
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123
SECTION 1: GENERATE AN ARGUMENT
10
CHARACTERISTICS OF VIRUSES
To share your work with others, we
will be using a round-robin format. This
means that one member of the group
will stay at your workstation to share
your group’s ideas while the other group
members go to the other groups one at a
time in order to listen to and critique the
arguments developed by your classmates.
Remember, as you critique the work
of others, you need to decide if their
conclusions are valid or acceptable based
on the quality of their claim and how
well they are able to support their ideas.
In other words, you need to determine
if their argument is convincing or not.
One way to determine if their argument
is convincing is to ask them some of the
following questions:
Figure 10.2. Components of the Whiteboard
The Research Question:
Your Claim:
Your Evidence:
Your Justification
of the Evidence:
• How did you analyze or interpret your data? Why did you decide to do it that way?
• How do you know that your analysis of the data is free from errors?
• Why does your evidence support your claim?
• Why did you decide to use that evidence? Why is your evidence important?
• How does your justification of the evidence fit with accepted scientific ideas?
• What are some of the other claims your group discussed before agreeing on your claim, and
why did you reject them?
124
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Appearance
3–4
Months
1–3
Months
1–10
Years
10
Years
10
Years
Organic
Compounds
Organic
Compounds
Organic
Compounds4
None
None
Energy
Source
Carbohydrates
Carbohydrates
Carbon Dioxide
None
None
Carbon
Source
No
Yes
None
None
None
No
Yes
Yes
No
No
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Nucleic Acid
Protein
None
Asexual6
Sexual5
Replication;
Requires a host
Replication;
Requires a host
None
DNA and
RNA
DNA and
RNA
DNA
RNA
No
Yes
Yes
No
No
Responds Biomolecules2
Waste
to External Present in the
Form of
Genetic
Production
Stimuli
Object
Reproduction Material3 Growth?
SCIENTIFIC ARGUMENTATION IN BIOLOGY: 30 CLASSROOM ACTIVITIES
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(continued)
1. 1 meter = 100 centimeters = 1000 millimeters = 1,000,000 micrometers = 1,000,000,000 nanometers
2. A biomolecule is any molecule that performs an important function in living organisms. Biomolecules are usually composed of hydrogen, carbon, oxygen, nitrogen, prosperous, or sulfur atoms
and they are organized into one of four main groups (carbohydrates, proteins, lipids, and nucleic acids).
3. The genetic material of an object is the molecule(s) that play the fundamental role in determining the nature and structure of an organism or cell.
4. Organic compounds are molecules that are composed of carbon such as sugar (which is a type of carbohydrate)
5. Sexual refers to a form of reproduction in which two parents give rise to an offspring.
6. Asexual refers to a form of reproduction that involves only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two parts.
8 micrometers
in diameter
Human Red
Blood Cell
500 micrometers
in diameter
Amoeba
3 millimeters
in diameter
Coriander
Seeds
220 nanometers
in diameter
Adenovirus
130 nanometers
in diameter
Influenza
Virus
Object and
Size1
Functional
“Life”
Span
Table 10.1. Information About Viruses and Other Objects Found on Earth
SECTION 1: GENERATE AN ARGUMENT
125
126
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45 centimeters
in height
Computer
0.75 meters
in height
Dog
1.5 meters
in length
Tube Worms
3 micrometers
in length
E. Coli
15 micrometers
in length
Plasmodium
Falciparum
40 centimeters
in length
Elodea
100 centimeters
in diameter
Sponge
10 micrometers
in diameter
Human White
Blood Cell
Object and
Size
Appearance
10–20 years
15–20 Years
100–200
Years
1–3 Months
1–2 Months
2–4
Weeks
100–200
Years
1
Month
Electricity
Organic
Compounds
Inorganic
Compounds
Organic
Compounds
Organic
Compounds
Sunlight
Organic
Compounds
Organic
Compounds
Functional
“Life”
Energy
Span
Source
None
Carbohydrates
Carbohydrates
Carbohydrates
Carbohydrates
Carbon Dioxide
Carbohydrates
Carbohydrates
Carbon
Source
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
None
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Nucleic Acid
Protein
Lipids
Carbohydrates
Responds Biomolecules
Waste
to External Present in the
Production Stimuli
Object
Table 10.1. Information About Viruses and Other Objects Found on Earth (continued)
None
Sexual
Sexual
Asexual
Sexual and
asexual but only
occurs inside a
host
Sexual and
asexual
Sexual and
asexual
None
None
DNA and
RNA
DNA and
RNA
DNA and
RNA
DNA and
RNA
DNA and
RNA
DNA and
RNA
DNA and
RNA
Form of
Genetic
Reproduction Material
SECTION 1: GENERATE AN ARGUMENT
NATIONAL SCIENCE TEACHERS ASSOCIATION
No
Yes
Yes
Yes
Yes
Yes
Yes
No
Growth?
SECTION 1: GENERATE AN ARGUMENT
CHARACTERISTICS OF VIRUSES:
What Is Your Argument?
In the space below, write an argument in order to persuade another biologist that your claim is valid
and acceptable. As you write your argument, remember to do the following:
• State the claim you are trying to support
• Include genuine evidence (data + analysis + interpretation)
• Provide a justification of your evidence that explains why the evidence is relevant and why it
provides adequate support for the claim
• Organize your argument in a way that enhances readability
• Use a broad range of words including vocabulary that we have learned
• Correct grammar, punctuation, and spelling errors
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