Topics Included: • Microorganisms → Bacteria → Protozoa → Algae → Fungi → Viruses • Friendly Microorganisms → Lactobacillus → Yeast • Antibiotics • Harmful Microorganisms • Common Human Diseases • Food Preservation • Methods of Food Preservation → Using Preservatives → Using Salt and Sugar → Using Vinegars → Using Pasteurization → Air Tight Packaging

1. MICROORGANISMS
FRIENDS & FOE
Class 8 Science

2. Bacteria
Protozoa
Algae
Fungi
Microorganisms

3. Bacteria
Lactobacillus Nitrogen Fixing Bacteria

4. Protozoa
Amoeba Paramecium

5. Algae
Spirogyra Chlamydomonas

6. Fungi
Bread mould Penicillium

7. Viruses show
both the
characteristics
of living and
non-living

8. FRIENDLY MICROORGANISMS
Lactobacillus turns
milk into curd.
Some bacteria are also
involved in the making
of cheese, pickles and
other food items.

9. FRIENDLY MICROORGANISMS
Yeast is used for commercial
production of alcohol and
wine.
This process of conversion
of sugar into alcohol is called
Fermentation.
Saccharomyces cerevisiae

10. FRIENDLY MICROORGANISMS
Antibiotics are manufactured
by growing specific
microorganisms and are used
to cure a variety of diseases.
Antibiotic

11. FRIENDLY MICROORGANISMS
In your childhood, you must
have been given injections to
protect yourself against
several diseases.
Vaccines

12. FRIENDLY MICROORGANISMS
Some bacteria and blue
green algae fix nitrogen from
the atmosphere to enrich soil
with nitrogen.
Blue green algae

13. HARMFUL MICROORGANISMS
Some microorganisms cause
diseases in human beings, plants
and animals.
These diseases causing
microorganisms are called
pathogens.

16. FOOD PRESERVATION
• Food left under moist
conditions is attacked by
microorganisms. It is called
Food Poisoning.
• Preventing it from spoiling is
called Food Preservation.

17. METHODS OF FOOD PRESERVATION
Using Preservatives
Using Salt and Sugar
Using Vinegars
Using Pasteurization
Air tight packaging