1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a ____________.
(b) Blue-green algae fix __________ directly from the air and enhance the fertility of the soil.
(c) Alcohol is produced with the help of __________.
(d) Cholera is caused by __________.
Ans:
a) Microscope
b) Nitrogen
c) Yeast
d) Bacteria- Vibrio cholera
2. 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
Ans:
a) (ii) alcohol
b) (ii) Streptomycin
c) (i) female Anopheles mosquito
d) (ii) housefly
e) (iii) growth of yeast cells
f) (iii) fermentation
3. Match the organisms in Column A with their action in Column B.
4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Ans:
Microorganisms cannot be seen with the naked eye because they are extremely small in size. However, they can be observed using a microscope, which magnifies these tiny organisms and makes them visible.
5. What are the major groups of microorganisms?
Ans:
The major groups of microorganisms are:
Bacteria
Fungi
Protozoans
Algae
Viruses
6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Ans:
The microorganisms that can fix atmospheric nitrogen in the soil are Rhizobium, Azotobacter, and blue-green algae (cyanobacteria like Anabaena and Nostoc).
7. Write 10 lines on the usefulness of microorganisms in our lives.
Ans:
The usefulness of microorganisms in our lives includes:
Microorganisms clean the environment by decomposing organic wastes like vegetable peels, animal remains, and faeces into harmless substances.
Bacteria such as Lactobacillus help in the formation of curd from milk.
Microorganisms like bacteria are used in the preparation of cheese, pickles, and other fermented foods.
Yeast aids in the fermentation of idli and dosa batter, making it fluffy.
In the baking industry, yeast produces carbon dioxide during respiration, which helps in making bread, pastries, and cakes soft and spongy.
Microorganisms like yeast are used for large-scale production of alcohol, wine, and acetic acid (vinegar).
Antibiotics, such as penicillin, are derived from bacteria and fungi to treat bacterial infections.
Vaccines for diseases like polio and smallpox are made using microorganisms.
Nitrogen-fixing bacteria like Rhizobium and Azotobacter enrich the soil with nitrogen and improve its fertility.
Microorganisms decompose dead plants and animals, converting them into nutrients that improve soil quality.
8. Write a short paragraph on the harmful effects of microorganisms.
Ans:
Microorganisms can have several harmful effects. They cause diseases in humans, plants, and animals. For example, Cholera in humans is caused by the bacterium Vibrio cholerae, while viruses cause diseases like foot and mouth disease in animals. Microorganisms spoil food by decomposing it, leading to food wastage and sometimes food poisoning. Fungi and bacteria can damage leather, wooden items, and clothes. Additionally, harmful microorganisms can release toxins into the environment, posing health risks.
9. What are antibiotics? What precautions must be taken while taking antibiotics?
Ans:
Antibiotics are chemical substances produced by microorganisms like bacteria and fungi that kill or inhibit the growth of disease-causing bacteria.
Precautions while taking antibiotics:
Antibiotics should only be taken on the advice of a qualified doctor.
The full course of prescribed antibiotics must be completed, even if one feels better.
Antibiotics should not be taken unnecessarily, as overuse can lead to antibiotic resistance.
Avoid self-medication, as taking the wrong antibiotic can worsen the condition.
Store antibiotics as directed and avoid using expired medicines.