Living science book 8th microorganisms Hots Questions :Think and anwser
Answers
Answer:
Q.(e) The bread or idli dough rises because of
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading
✔ Q.(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation
(ii) moulding
(iii) fermentation
(iv) infection
✔ Q.3. Match the organisms in Column I with their action in Column II.
Column I
Column II
(i)
Bacteria
(a)
Fixing nitrogen
(ii)
Rhizobium
(b)
Setting of curd
(iii)
Lactobacillus
(c)
Baking of bread
(iv)
Yeast
(d)
Causing malaria
(v)
A protozoan
(e)
Causing cholera
(vi)
A virus
(f)
Causing AIDS
(g)
Producing antibodies
.4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Microorganisms are too small so they cannot be seen with naked eye. They can be seen with the help of a magnifying glass or microscope.
Q.5. Explain major groups of microorganism.
Ans. It consists of five major groups :
(a) Algae – They are Spirogyra, Chlamydomonas which are multicellular, photosynthetic organism.
(ii) Virus – They are microbes which cause disease and they reproduce only inside the host.
(iii) Protozoa – They are unicellular or multicellular organisms such as Amoeba, Plasmodium.
(iv) Bacteria – They are either spiral or rod-shaped. These micro-organisms are disease-causing single-celled organisms.
Q.6. What is the micro-organism which is used in the fixation of atmospheric nitrogen into the soil?
Ans. Fixation of atmospheric nitrogen and converting them into useful nitrogen compounds is done by bacteria such as blue-green algae and Rhizobium. Plants use these nitrogenous compounds to synthesise the necessary plant proteins and other compounds.
Q.7. How are micro-organisms useful in our lives?
Ans.
Micro-organisms are not visible to the naked eye but they are necessary to plants and environment.
In baking, pickling, winemaking and other food making process, these micro-organisms are used. In the preparation of wine and bread, alcoholic fermentation by yeast is used. For the curd formation, a bacterium Lactobacillus is used.
Bacteria and fungi help to decompose dead bodies and excreta which forms inorganic compounds that are absorbed by plants.
Bacteria such as Rhizobium and blue-green algae help to fix atmospheric nitrogen in the soil.
In the preparation of medicines, microbes are used. Micro-organisms produce antibiotics to kill bacteria. Streptomycin is an antibiotic.
Treatment of sewage and industrial effluents are done by certain microbes.
Q.8. What are the harmful effects of microorganisms?
Ans.
Micro-organisms can cause diseases. Tuberculosis, cholera, typhoid are caused by bacteria in humans. In cattle, the virus causes foot and mouth disease. Diseases in plants are caused by several microbes. Microbes produce toxic substances when they enter our body and this leads to food poisoning. Food is spoiled by microorganisms like fungi. Under moist conditions, when the bread is left unused, it gets spoiled by a fungus causing white cotton-like growth on its surface.
Q.9. Explain about antibiotics. When taking them, what precautions must be taken?
Ans.
Micro-organisms produce antibodies to eliminate other micro-organisms that cause disease. Bacteria and fungi are used to obtain these medicines. Common antibiotics are Streptomycin, tetracycline, etc.
Precautions when taking antibiotics:
(a) Antibiotics are to be taken only under the surveillance of a well-qualified doctor.
(b) As per the prescription is given by the doctor, the antibiotics are to be taken.
(c) Antibiotics are to be taken in the right dose at the right time. The drug is ineffective if it is taken in the wrong dose and may kill the useful bacteria present in the body if it is taken in excess.
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