Chapter 2 Microorganisms Friend and Foe Solutions
Question - 1 : - Fill in the blanks.
- Microorganisms can be seen with the help of a………………
- Blue green algae fix………….. directly from air and enhance fertility of soil.
- Alcohol is produced with the help of……………….
- Cholera is caused by………………….
Answer - 1 : -
- microscope
- nitrogen
- yeast
- 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
Answer - 2 : -
(a) (ii) alcohol
(b) (ii) Streptomycin
(c) (i) female Anopheles mosquito
(d) (ii) housefly
(e) (iii) growth of yeast cells
(f) (iii) fermentation.
Question - 3 : - Match the organisms in Column A with their action in Column B. | Column A | Column B |
| (i) Bacteria (ii) Rhizobium (iii) Lactobacillus (iv)Yeast (v) A protozoan (vi) A virus | (a) Fixing nitrogen (b) Setting of curd (c) Baking of bread (d) Causing malaria (e) Causing cholera (f) Causing AIDS (g) Producing antibodies |
Answer - 3 : -
| Column A | Column 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 |
Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer - 4 : -
The microorganisms are so small in size that they cannot be seen with the naked eye. Some of these, such as fungus that grows on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope. That is why these are called microorganisms or microbes.
Question - 5 : - What are the major groups of microorganisms?
Answer - 5 : -
Microorganisms are classified into four major groups based on their size. These are:
- Bacteria
- Fungi
- Protozoa
- Some algae.
Viruses are another type of microorganisms.
Question - 6 : - Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer - 6 : -
Rhizobium, Clostridium and Azotobactor.
Question - 7 : - Write 10 lines on the usefulness of microorganisms in our lives.
Answer - 7 : -
Microorganisms are useful for us in many ways e.g.,
- bacterium, lactobacillus convert milk into curd.
- bacteria are also involved in the making of cheese.
- Acetobacter aceti is used for production of acetic acid from alcohol.
- Yeast is used for commercial production of alcohol and wine.
- Antibiotics are manufactured by growing specific microorganisms.
- Some bacteria fix atmospheric nitrogen and increase the soil fertility.
- Bacteria are used in the preparation of medicines like antibiotics and vaccines.
- Bacteria are used in the preservation of pickles and many other food items.
- Yeast is also used in baking industry for making breads, pastries and cakes.
- They act as cleansing agent and decompose the waste products into manure.
Question - 8 : - Write a short paragraph on the harmful effects of microorganisms.
Answer - 8 : -
Microorganisms which cause diseases in men, animals and plants, are called pathogens. Pathogens or germs enter a healthy body through air, water, contaminated food and an infected person by direct or indirect contact or by a carrier. Common ailments like cold, influenza (flu), coughs, polio, chicken pox are caused by viruses. Foot and mouth diseases of cattle are also caused by viruses. Typhoid, tuberculosis (TB) are caused by bacteria. Anthrax a dangerous human and cattle disease is also caused by bacteria. Disease like dysentery and malaria are caused by protozoa. Ringworm is caused by fungi. Some microorganisms release toxic substances when they grow on food. Citrus canker is a bacterial disease that affects trees of citrus fruits and is spread by air. Yellow vein mosaic disease is caused by insect in bhindi. Rust of wheat is a fungi disease spread by air.
Question - 9 : - What are antibiotics? What precautions must be taken while taking antibiotics?
Answer - 9 : -
Antibiotics are the medicines which kill or stop the growth of the disease causing microorganisms. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases.
It is important to remember that antibiotics should be taken only on the advice of a qualified doctor. Also you must finish the course prescribed by the doctor. If you take antibiotics when not needed, you help bacteria in your body to develop resistance to them. Next time when you fall ill and need these antibiotics, they would be less effective. Antibiotics, however, are not effective against cold and flu as they are caused by viruses.