Class 8 - Biology - Microorganisms: Friend and Foe
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ____________.
(b) Blue green algae fix __________ directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of __________. (d) Cholera is caused by __________.
(a) Microorganisms can be seen with the help of a microscope.
(b) Blue green algae fix nitrogen directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of microorganisms.
(d) Cholera is caused by bacteria.
Tick the correct answer:
(a) Yeast is used in the production of (i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
(b) The following is an antibiotic (i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast
(c) Carrier of malaria-causing protozoan is (i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly
(d) The most common carrier of communicable diseases is (i) ant (ii) housefly (iii) dragonfly (iv) spider
(e) The bread or idli dough rises because of (i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading
(f) The process of conversion of sugar into alcohol is called (i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection
(c) Female Anopheles mosquito
(e) Growth of yeast cells
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
(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
Can microorganisms be seen with the naked eye? If not, how can they be seen?
No, microorganisms cannot be seen by naked eye as they are very small and are called microbes. They can be seen with the help of microscope.
What are the major groups of microorganisms?
Microorganisms are classified into four major groups are bacteria, fungi, protozoa and some algae. They vary in size and mode of nutrition.
Name the microorganisms which can fix atmospheric nitrogen in the soil.
Bacteria such as rhizobium and certain blue-green algae present in the soil can fix atmospheric nitrogen and convert into usable nitrogenous compounds,
which are used by plants for the synthesis of plant proteins and other compounds.
Write 10 lines on the usefulness of microorganisms in our lives.
Microorganisms are too small to be seen through naked eyes. However, they are vital to plants and the environment. Importance of microorganisms:
Write a short paragraph on the harms caused by microorganisms.
Microorganisms are harmful in many ways.
What are antibiotics? What precautions must be taken while taking antibiotics?
The medicines that kill or stop the growth of the bacteria are called antibiotics.
They are used only against bacterial infections. For example: Streptomycin, tetracycline, etc.
Following precautions must be taken while taking antibiotics: