8th grade
Viruses
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A Virus is a tiny, nonliving particle that enters and then reproduces inside the living cell.
Viruses can infect any size organism.
Viruses are considered nonliving because they are not cells, they do not use their own
energy to grow, they can not respond to their environment, they cannot make food or take
in food, they do not produce waste. The only way they are like living organisms is that they
can multiply but they need a living cell to do so.
The relationship that exists between a virus and a cell is a parasitic relationship. The cell
would be a host. A host is an organism that provides a source of energy for a virus. The
virus would be a parasite. A parasite is an organism that lives on or in a host and causes it
harm. Viruses usually destroy the cells where they are multiplying.
Two main shapes for viruses Round and Robot.
All viruses have 2 basic parts: a protein coat that protects the virus and an inner core made
of genetic material (DNA)
Virus proteins act like keys to fit the locks of the host cell’s outer proteins. The virus can
only enter the cell if the key fits the lock. This is why the cold virus only affects the cells in
the nose and throat.
Once a virus’s genetic material is inside the cell the host cell produces the virus’s genetic
material and proteins in order to make new viruses.
Viruses, Bacteria, and your Health
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An infectious disease is an illness that passes from one organism to another. Infectious
diseases can spread through contact with an infected person, a contaminated object, an
infected animal, or an environmental source.
Contact with an infected person through touching, hugging, or kissing can spread infectious
diseases. Contact can occur indirectly, like inhaling tiny drops of moisture in the air after
someone has sneezed or coughed. These droplets carry the disease causing organisms.
Contact with a contaminated object: Some viruses and bacteria can survive outside the
body and can be spread by sharing eating utensils, drinking after someone, and even
touching a doorknob. After touching one of these objects and then touching your face or
eyes spreads the disease very quickly.
Infected animals can transmit some serious infectious diseases to humans. Animals that
transmit diseases act as vectors, like how ticks can transmit the bacteria that causes Lyme
disease and the Mosquito that spreads yellow fever and the virus encephalitis.
Viruses and bacteria live in the natural environment. Poultry, Eggs, and meat often contain
a harmful bacterium that causes food poisoning, which is why it is important to cook food
thoroughly. Tetani is a soil-dwelling bacterium that can enter a person’s body through a
wound, like stepping on a nail. This bacteria produces a poison, called tetanus, and can be
deadly.
8th grade
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Treating an infectious disease is fortunately not too difficult since most can be cured with
antibiotics. An antibiotic is a chemical than can kill or weaken bacteria without harming a
person’s cells. Some bacteria and fungi make antibiotics naturally. Penicillin works by
weakening the cell walls of some bacteria and causing the cells to burst. Unfortunately
antibiotics are less effective today than they once were. Bacteria have become resistant to
antibiotics. In the 1940s tuberculosis was almost eradicated but some forms of the disease
was resistant to the antibiotics and so they began to multiply and the results have shown I
an increases number of cases in recent years.
Common Bacterial Diseases to know
o Lyme Disease
 Caused from a bite by a deer tick
 Rash at site of bite, chills, fever, body aches, swelling joints
o Tuberculosis (TB)
 Air-born bacteria
 Fatigue, mild fever, weight loss, night sweats, cough
o Tetanus
 Deep puncture wound by dirty object
 Stiff jaw and neck muscles, spasms, difficulty swallowing
o Food Poisoning
 Eating foods contaminated with bacteria (Salmonella and E. Coli)
 Vomiting, cramps, diarrhea, fever
o Strep Throat
 Inhaling or contact with object contaminated with streptococcus bacterium
 Fever, sore throat, swollen glands
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Viral diseases do not have a cure. Over-the-counter medications are typically taken to help
elevate the symptoms that accompany the viral infection. The best treatment for a viral
disease is bed rest, drinking lots of fluids, and eating well-balanced meals.
Common Viral Diseases to know
o Influenza (Flu)
 Contact with contaminated objects, inhaling air-born droplets
 High fever, sore throat, headache, couch
o Chickenpox
 Direct contact with rash, inhaling droplets
 Fever, red-itchy rash
o Acquired Immuno-Deficiency Syndrome (AIDS)
 Sexual contact, contact with blood, pregnancy, birth, and breastfeeding
 Weight loss, chronic fatigue, fever, diarrhea, frequent infections
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Preventing infectious diseases: Vaccines are useful tools to help prevent the spread of
infectious diseases. A vaccine is a substance introduced into the body to stimulate the
production of chemical that destroy specific viruses or bacteria. A vaccine may be made
from dead or altered viruses or bacteria; because of this the vaccine does not cause the
8th grade
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disease. So that if the virus or bacterium invades the body it will be destroyed before it can
cause the disease.
Other easy ways to help the spread of disease is by eating healthy, drinking plenty or water,
and getting enough rest. Also washing your hands often and not sharing drinks or food is a
good method of disease prevention.
Antibiotic Resistance
Antibiotics were first available in 1943 and were considered to be a wonder drug.
Down side to the wide use of antibiotics is: Each time an antibiotic is used, a few resistant
bacteria may survive and pass on their resistance to the next generation of bacteria.
If doctors would better identify the cause of an infection, they could avoid prescribing
unnecessary antibiotics.
If a doctor prescribes a 10-day course of antibiotics make sure to take the entire
prescription to make sure all the bacteria have been killed. If a patient stops taking the
antibiotic, resistant bacteria will survive and reproduce. Which can cause for a need in
another type of antibiotic.
General viral appearance
General Bacterial appearance
Amoeba
Paramecium