The microorganisms that fix atmospheric nitrogen in the soil are Rhizobium and blue-green algae. These microorganisms are commonly called biological nitrogen fixers that fix atmospheric nitrogen to enrich soil with nitrogen and increase the fertility of soil.
Microorganisms are classified into four major groups. The four major groups of microorganisms are:
No, microorganisms cannot be seen with the naked eye. They are too small to be seen with naked eye. They can be seen through magnifying lens and microscope. Microorganisms, such as protozoans, present in water can be seen under a microscope. Fungus, that grows on bread, can be seen with the help of a magnifying lens.
(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria
Antibiotics are the medicines that are produced by the microorganisms to kill the disease causing microorganisms. The microorganisms that are used to prepare the antibiotics are bacteria and fungi.
The precautions that are to be taken while taking antibiotics are:
Microorganisms cause harm in many ways. Some of the harmful effects of microorganisms include causing diseases in humans, animals and plants and spoiling of food, clothes and leather. The disease causing microorganisms are called pathogens. Some bacterial microorganisms cause tuberculosis, typhoid, cholera, etc. in human beings. Diseases, like measles, chickenpox, polio, hepatitis, etc., are caused by viruses in human beings. In cattle, anthrax is caused by bacteria and foot and mouth disease is caused by fungi. In plants, disease like citrus canker, rust of wheat and yellow vein mosaic of bhindi are caused by bacteria, fungi and virus, respectively and reduces the yield of crops. Some microorganisms, like bacteria and fungi, spoil food by producing toxic substances. When these microorganisms are ingested by human beings along with the spoiled food, food poisoning is caused.
A | B |
(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 |
A |
B |
(i) Bacteria |
(e) Causing cholera |
(ii) Rhizobium |
(a) Fixing nitrogen |
(iii) Lactobacillus |
(b) Setting of curd |
(iv) Yeast |
(c) Baking of bread |
(v) A protozoan |
(d) Causing malaria |
(vi) A virus |
(f) Causing AIDS |
(a) (ii) alcohol
(b) (ii) Streptomycin
(c) (i) female Anopheles mosquito
(d) (ii) housefly
(e) (iii) growth of yeast cells
(f) (iii) fermentation
Following are some functions of microorganisms that are important to us:
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