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Exploring Life Science
Chapter 5
Viruses & Bacteria
CHAPTER 7: Viruses, Bacteria, Protists, and Fungi
Engage: Discuss HIV (We are not going to use “handson” when we study this).
Journal Activity: How do viruses affect you?
7-1: Viruses
A. Virus – Tiny, nonliving particle that invades and
then multiplies inside a living thing.
1. Smaller than a cell.
2. Living or non-living?
CAN
CANNOT
Reproduce -- but
most have a host.
Perform all the
functions of
living things:
-- take in food
-- get rid of wastes
3. Host -- Living thing that provides a home and/or
food for a parasite.
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Exploring Life Science
Chapter 5
Viruses & Bacteria
4. Parasite -- An organism that survives by living
on or in a host organism, thus harming it.
(i.e., rabies -- infect nerve cells of mammals).
5. Origin -- Unknown.
Believe viruses evolved from bits of hereditary
material that were lost from host cells.
B. Structure
1. Parts
 Core of DNA -- Control reproduction.
 Outer coat of protein -- Protection.
2. Many Sizes and Shapes
 Most - Round
 Triangles, threads & spheres - spaceships.
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Exploring Life Science
Chapter 5
Viruses & Bacteria
C. Reproduction
i.e., Bacteriophage virus infects bacteria – (“bacteria
eater”)
1.
2.
3.
4.
5.
Attaches tail to bacteria.
Injects DNA.
Protein coat left behind.
Inside DNA takes control of bacteria activity.
Bacteria begins to produce new bacteriophages
rather than its own.
6. Bacteria fills up with new bacteriophages eventually bursts open.
7. New bacteriophages are released.
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Exploring Life Science
Chapter 5
Viruses & Bacteria
First: Virus gets its DNA into host cell.
Second: Host cell gets more virus.
Third: Virus leaves the original host cell and
infects new hosts.
D. Active and Hidden Viruses
1. Active – Enter cell and immediately goes into
action.
2. Hidden – Do not immediately become active.
“Hide” for a while. Ex. Cold Sores
E. Viruses & Humans
1. Cause diseases (cold, fever blisters, warts,
AIDS, measles, influenza, hepatitis, smallpox,
polio, encephalitis, mumps, & herpes).
2. Spreading
 Contact
 Bites
 Drops of moisture from sneezes or coughs.
 Body fluids – blood etc.
3. Treating
 No Cures
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Exploring Life Science
Chapter 5
Viruses & Bacteria
 Relieve symptoms – Medications
 Rest, drinking fluids, eating well-balanced
meals.
4. Preventing
 Vaccine - substance put into the body to
stimulate the production of chemicals that
destroy specific viruses. (Weakened or
altered viruses). Put body on alert.
Have them for: Polio, measles, and
chickenpox.
 Keep your body healthy.
 Washing hands
5. Help -- used to make some vaccines.
Stimulates production of antibodies.
Germ Warfare -- (i.e., killed 80% of
rabbits in Australia).
Viruses better weapon than poisons
because they are “selective” –
poisons are not.
6. Used to put DNA into cell -- maybe cure
diseases, improve crops.
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Exploring Life Science
Chapter 5
Viruses & Bacteria
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