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Lesson 2 Microorganisms: Friends or Foes.
A. Fill in the blanks.
1. The study of microorganisms is known as microbiology.
2. The bread dough rises because of the production of carbon dioxide
3. Pathogens are the microorganisms that cause diseases.
4. Potassium metabisu and Sodium benzoate are two chemical preservatives.
5. Aspergillus is a fungus that causes food poisoning.
B. Match the following.
1. Ringworm - fungus.
2. Clostridium - food poisoning.
3. Anthrax - cattle.
4. Lactobacillus - curd.
5. Methane - biogas reactor.
C. Tick (✓) the correct option.
1. The process, that helps milk to last longer but does not kill all microbes present in it, is known as-
vaccination
bioaugmentation
pasteurisation ✓
fermentation.
2. Rust of wheat is caused by-
fungus ✓
bacteria
virus
protozoa.
3. Medicines, containing killed or weakened pathogens, and used to prevent infectious diseases, are called-
disinfectants
antibodies
antibiotics
vaccines ✓.
4. Which of the following reproduces only inside a host cell?
virus ✓
alga
protozoan
bacteria.
5. A disease, caused by a virus, and spread by an insect, is-
polio
dengue ✓
rabies
mumps.
D. Answer the following questions in brief.
1. Why are viruses considered as being at the 'borderline' between living and non-living things?
Ans. A virus behaves like a living being when it is outside a host Cell .Once a virus enters a host, it becomes a living organism. Due to this viruses are considered as borderline between living and non-living.
2. What is fermentation? How is this process useful in the food and beverage industries?
Ans. Fermentation is an anaerobic process through which Sugars or carbohydrates are converted into alcohol or acids and carbon dioxide by the action of microbes.
Fermentation is useful in the food and beverage industries in the following ways:-
a. Lactobacillus is a bacterium that helps in the formation of curd.
b. Fungi, like yeast is reproduces rapidly and produce carbon dioxide. When this gas is trapped in dough,it increase its volume and make idli, dosa ,cake and cookies fluffy and soft.
c. The process of fermentation is useful in alcoholic beverages as fungi, like yeast, convert natural sugar present in cereals and fruits into alcohol. This alcohol is then used to make alcoholic beverages.
d. Acetic Acid, commonly known as vinegar, is also produced by a similar process.
3. 'In the absence of microorganisms the earth would become a heap of Dead plants and animals'. Justify this statement.
Ans. It is true that in the absence of microorganisms the earth would become a heap of dead plants and animals because microorganisms helps in decomposing the dead plants and animals .They helps in recycling of materials, cleaning up waste and creating space for growth of new organisms.
4. Munna observes that the yield of wheat, growing in his field, has reduced in the current year.
He gets the soil testing and the report confirms the deficiency of one particular nutrient. Accordingly, he is advised to grow Peas after harvesting wheat.
Ans. (i) Name of the nutrient found in sufficient is nitrogen.
(ii) Leguminous crops like peas give shelter to rhizobium bacteria. These bacteria carry out nitrogen fixation in soil. Thus, pea plants help in replenishing nitrogen in soil.
5. Why does it take less time to prepare curd in summer as compared to preparing it in winters?
Ans. Micro organisms reproduce at a faster rate between the temperature range 30°C to 45°C . They reproduce at a much slower rate when temperature is below this range. Milk is converted into curd by multiplication of lactobacillus .This is why it take less time to prepare curd in summer as compared to preparing it in winters.
6. How are the following diseases transmitted:
a) Malaria
b) common cold
c) Tetanus
d) Typhoid
Ans. a) Malaria: By female Anopheles Mosquito.
b) Common cold: through cough droplets in air
c) Tetanus: soil
d) Typhoid: through contaminated food and water
7. What are antibiotics? How are they produced? Give two examples of these.
Ans. Antibiotics are special chemicals which kill pathogens.
Antibiotics are produced by using some fungi and also by certain synthetic chemicals.
The two examples of this is streptomycin and tetracycline.
Explanation: