Viruses are non-living particles that enter and reproduce inside living cells. They act as parasites and cannot grow or produce energy on their own. Viruses have either DNA or RNA as their genetic material surrounded by a protein coat and sometimes a membrane envelope with surface proteins. These surface proteins help viruses invade host cells. While viruses can cause disease, they can also be used to treat and prevent illnesses through vaccines where a weakened form of the virus is introduced to the body to produce antibodies without causing disease.

1. Viruses
II Bimestrial
Sixth Grade
Ms. Matta
Science Class
Chapter 2
Lesson 1

2. Unlock the Big ?
What are the characteristics of
viruses?
How do viruses interact with the
living World?

3. My Planet Diary
A Mad Choice
• Have you ever seen a
snarling dog on TV?
Chances are this
“mad dog” was
supposed to have
rabies. Rabies is a
virus that affects the
brain, causing “mad”
behaviors and
spasms of the throat.
• Infected animals
avoid water, giving
the disease the
nickname
hydrophobia,
meaning “fear of
water”. In the
1800s, if people
were bitten by a
mad dog, they
would likely die.

4. Vocabulary Lesson 1
• Virus
• host
• parasite
• vaccine

5. Key Concepts
• Virus: Is a tiny, nonliving particle that enters and
then reproduces inside the living cell.
• host: Is an organisms that provides a source of
energy for a virus or another organism.
• parasite: An organisms that lives on or in a host
and causes it harm.
• vaccine: Is a substance introduced in the body to
help produce chemicals that destroy specific
viruses.

6. Virus
Host
Parasite
Vaccine

8. What are the characteristics
of the viruses?
1. Viruses are not cells.
2. Virus can not use their own energy to grow or
develop.
3. Can not make food, take in food or produce
wastes.
4. Can multiply like organisms, when they are inside
a living cell.
5. A virus acts like a parasite.

9. Generic material
Cell’s Surface proteins
Protein coat
Virus’s
surface
protein
Membrane
envelope
Host cell

10. The structure of viruses
• Genetic material
• Protein coat
• Membrane envelope
• Virus surface proteins

11. How do viruses interact with
the living world?
• Through viruses can cause disease, they can also
be used to treat and prevent illnesses.

12. Vaccine Protection
1. The virus
that causes a
disease is
isolated. The
virus is then
weakened or
killed by
heat, and a
vaccine is
prepared
from it.
2. During
vaccination,
the
weakened
virus is
injected into
the body.
3. The body
prepares
defense
against the
virus.
4. The body
can now
resist
infection by
the disease
causing
virus.

13. Asses your understanding
• 1. A virus is a living/nonliving particle that enters a
cell and uses it to reproduce.
• 2. Cause and Effect: How to the surface proteins on
a virus help it to invade a host cell?
• 3. Challenge: Scientists hypothesize that viruses
could not have existed on Earth before organisms
appeared. Do you agree? Explain.