MICROORGANISMS - FRIEND AND FOE, Class 8

MICROORGANISMS - FRIEND AND FOE

Q1. What is a microorganism ?
Ans:- A microorganism is a living organism that is very minute. It can only be seen with the aid of a microscope.
Q2. What are the habitat of microorganisms ?
Ans :-(i) Microorganisms are present everywhere in air, soil, water, foodstuffs, sewage waste as well as inside animal bodies.
(ii) They can survive in all types of environment even in extremely harsh environmental conditions like hot springs, desert soil, saline water, ice - cold water and marshy lands.
(iii) They are also present in dead and decaying organic matter.
(iv)Some of them can live alone while others in colonies.
Q3. What are the major groups of microorganisms ?
Ans :- (i) Bacteria (ii) Fungi (iii) Protozoa (iv) Algae (v) Viruses
Q4. What are bacteria?
Ans :- Bacteria are single celled organisms, found in a wide range of habitats ranging from glaciers to deserts and hot springs. examples - Lactobacillus ( curd bacteria ).Bacteria are generally heterotroph but some bacteria also show autotrophic nutrition.
Q5. What are fungi ?
Ans :- Fungi are multicellular, heterotrophic organisms, lack of chlorophyll and are generally found in colonies.
Exception - Yeast is unicellular in nature e,g., Penicillium, Aspergillus.
Q6. What are protozoa?
Ans :- Protozoa are unicellular , heterotrophic microorganisms. They are usually found in moist and aquatic habitats. Examples- Amoeba, Paramecium.
Q7. What are algae ?
Ans :- These are unicellular or multicellular eukaryotic autotrophic organisms, contain chlorophyll pigment and carry out photosynthesis. Cell wall of algae is mainly made up of cellulose. Examples - Chlamydomonas, Spirogyra, Chlorella.
Q8. What are viruses?
Ans :- Viruses are acellular structures because they are not built up of cells.They are much smaller than cells. These are ultramicroscopic organisms, which require cells of host organisms to reproduce.
Examples - Influenza virus, polio virus, AIDS etc.,. Structure of the virus consists of nucleic acid and a protein coat. nucleic acid can either be DNA or RNA.