Microorganisms, or microbes, are very small organisms that can only be seen with magnification. They exist as either single-celled or multi-celled structures and can be found in nearly all environments, including inside other living things. Microbes are divided into three kingdoms: fungi, monera, and protoctista. Fungi include mushrooms and yeasts, while monera contains bacteria and blue-green algae consisting of single cells without nuclei. Protoctista encompass single-celled organisms that have nuclei and include amoebas, flagellates, and ciliates. Viruses are not considered living but can still reproduce by entering and using host cells. Many microbes play important

2. Microorganisms (Microbes) :-
• i) Microorganisms are very small organisms which cannot be seen
with the naked eye. They can be seen only with a magnifying glass
or microscope.
• ii) Microorganisms may be unicellular or multicellular.

3. Microorganisms (Microbes) :-
• iii) Microorganisms may exist alone or in colonies.
• iv) Microorganisms are found in all kinds of environment like ice cold
climate, hot springs, deserts, etc. They are also found inside the
bodies of other organisms.

4. Micro-organisms are divided into 3
kingdoms
Fungi Monera Protoctista

5. Mushroom Yeast

6. A few fungi are parasites. Athlete’s foot is caused by
a fungus that feeds on damp skin between toes.

7. Useful Yeast
- Bread is made by mixing flour, yeast, water and sugar into dough.
- The yeast respires in the dough using the sugar and produces
bubbles of co₂ that makes the dough rise.
- When bubbles of gas are heated they expand so the dough is
placed in a warm cupboard for about half an hour to make the
dough rise

8. They are microscopic bodies made from just one cell.
The cell does not have a nucleus.
They are two groups in this kingdom:
Bacteria Blue green algae

9. Bacteria
- Bacteria can be found almost everywhere (In air, water on rocks
and inside living things too).
- They have spherical, spiral or rod shaped.

10. Diseases caused by harmful bacteria
- Diphtheria
- Whooping cough.
- Cholera.

11. - Typhoid fever
- Tuberculosis.
- Food poisoning.

12. Useful bacteria
- Yoghurt is made by putting certain type of bacteria to milk and
make it turn sour.
- Vinegar is made by allowing other bacteria to feed on
ethanol(alcohol) and change it to acetic acid.

13. Blue green algae
- They live in seas, oceans and lakes.
- They can also grow on wet rocks, at the sides of stream
and rivers and the tops of rocky sea shores.
- When they occur in large numbers they can be seen.

14. The living things in Protoctista kingdom
have microscopic bodies made from just
one cell which contains a nucleus.
Amoeba Flagellate Ciliate

15. - Protoctista live in aquatic habitats
or damp places (soil).
- Some make their own food by
photosynthesis and are called
unicellular plants (Protophyta).
- Other members feed as animals
do and are called unicellular
animals (Protozoa)

16. How Protoctista move?
Flagellum
- Single long hair (In
flagellates).
- They lash the flagellum
like a whip to move.
Cilia
- Coating of ting hairs (In
Ciliates).
- They wave the cilia to
and fro to move.
Pseudopodia
- False feet (In amoeba).
- Make projections from
its body wall to move.

17. Do not have cell structure.
- Viruses can be stored for many years without changing (they
do not eat, respire or excrete).

18. How do Viruses reproduce?
- When they are placed on living
tissue they enter the cells and
reproduce.

19. Diseases caused by viruses
- Each kind of virus attacks certain
cells in the body.
- Ex. Cold virus attacks the cells
that line the inside of the nose
the destructive action of the virus
causes the nose to run.
- Viruses also cause influenza,
chicken pox, measles and rabies.

20. Many microorganisms have a very important part in making sure
that life on earth continues.

22. Decomposers break
down dead plants
and animals into
minerals (released
into the soil)
Plants take in the
minerals in the soil to
grow.
Animals eat the
plants.
Animals eat the
herbivores.

24. - Louis Pasteur (1822 -1895) was a French scientist (made many
discoveries about microorganisms).
- Before Louis Pasteur began his work people believed in an
idea called the spontaneous generation.
- Spontaneous generation: Living things come grow from non-
living things.
- Ex.: Maggots came from raw meat.
Mice from wheat.
Beetles from cow dung.

26. - Louis Pasteur (concluded from his experiments that whatever
is causing the change can be carried by air, but it must be
heavier than air because it settled in the bend in the swan
neck.
- He called the tiny objects spores.

27. - After realising that broths where made bad by
microorganisms, Pasteur reasoned that microorganisms can
cause disease in animals and in humans.
- Pasteur developed the theory called the GERM THEORY.
- The Germ theory states that many diseases are cause by
microorganisms invading the body.