class 8th chapter 2 microorganisms friends and foe

1. Chapter 2
Notes

2. Microorganisms
(microbes)
1. Microorganisms can be seen only under a mic
2. They can be multicellular or single cellular.
3. They can be found in every kind of
environment like hot cold rainy etc.

3. Types of microorganism
1. Bactria
2. Algae
3. Virus
4. Protozoa
5. Fungi

4. Scientific study of
microorganism is called
microbiology.

5. Bactria
1.Bactria are single celled organism.
2.It is scattered in the cytoplasm.
3. Shapes of Bactria are :- rod, spiral, ro
4. Round =coccid
rod = Bactria
spiral = spiral

6. Algae
1. oceans, lakes, rivers, ponds and even in snow,
anywhere on Earth.
2. algae grow in ponds, lakes, rivers, streams,
oceans, puddles and waterfalls.
3. Algae require few thing to grow :- sunlight ,
water , carbon, and nutrients like nitrogen and
phosphorus.

7. Virus
1. a non-cellular, infectious entity composed of gene
2. Lies on the surface or borderline of other living a
3. Covid , chicken pox , common cold etc and many m

8. Fungi
1. Fungi are heterotrophs .
2. They live in or on other plants.
3. Fungi reproduce by spreading microscopic

9. protozoa
1. Protozoa are one-celled animals found worldwide in
2. They are mostly aquatic .
3. example :- amoeba , paramecium .

10. Types of disease

11. Friendly
microbes
1. Making curd from milk :- The bacterium
called lactobacillus
2. Making bread :- The fungus called yeast reproduce
carbon dioxide which makes the dough soft
3. Making alcohol :- yeast is used for commercial
for making alcohol and wine
4. Making medicines :- Some Bactria and fungi
are used to make medicines that stop or kill the
growth of disease causing microbes known as
antibiotics

12. Fertile soil
Some bacteria like rhizobium
and blue green algae are able
to fix nitrogen gas from the
atmosphere to enrich the
soil with nitrogen compounds
and increase its fertility.

13. Clean environment
They decompose dead and
decaying matter from
plants and animals,
convert them into simpler
substances which are
later used up by other
plants and animals.

14. Harmful Bactria
1. Some microorganism cause disease in plants
and animals . Such microorganisms are called
pathogens.
2. Some microorganisms spoils material like clothing,

15. Pathogens
any organism that can
produce disease. A
pathogen may also be
referred to as an
infectious agent, or
simply a germ.

17. Nitrogen cycle