Biology Important Question: Microbes in Human Welfare

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1 Mark Questions

Fill in the blanks:

  1. Yabuta & Sumiki isolated gibberellins from infected rice seedlings.
  2. Traditionally amylase, papain and ________ were used in food processing.
  3. Nitrogen-fixing (Rhizobia) bacteria show symbiotic association with a bean.
  4. Anabaena shows association with aquatic fern Azolla.
  5. A strain of yeast, Saccharomyces cerevisiae var.ellepsoideus is used in industrial production of wine.

Give one scientific name of the organism for the following :

Q1. Free-living nitrogen-fixing bacteria

  • Cyanobacteria

Q2. A major source of methanogens in the production of biogas.

  • Acetic acid

Q3. Microbe producing citric acid.

  • Aspergillus niger

Q4. Bacteria that cause curdling of milk.

  • Lactobacillus Lactic acid Bacteria (LAB)

Q5. Microbes used in the production of cellulase.

  • Trichoderma konigi

Answer the following in one sentence :

Q1. Give the full form of VAM.

  • the full form of VAM is Vesicular Aarbuscular Mycorrhizae.

Q2. Enlist the microbes used in dairy industry.

  • The microbes commonly used in the dairy industry are species of Streptomyces, Penicillium and Lactobacillus.

Q3. Name the cells in blue-green algae that are sites of nitrogen fixation.

  • The cells in blue-green algae that are sites of nitrogen fixation are cyanobacteria.

Q4. Name the bacteria forming a symbiotic association with roots of a pea plant.

  • Rhizobia are the bacteria forming a symbiotic association with roots of a pea plant.

Q5. Name the pathogenic fungi that are used as a herbicide.

  • The pathogenic fungi that is used as a herbicide is Collectrichum gloeosporioides

Q6. Which bacteria bring about anaerobic digestion in the biogas plant.

  • Methanogenic bacteria bring about anaerobic digestion in the biogas plant.

Q7. Enlist the steps involved in the production of beer.

  • Beer is produced through various steps like maltin, mashing, and fermentation.

Q8. State the microbial source of gibberellins.

  • The microbial source of gibberellins is fungus Gibberella fujikuroi.

Q9. Which vitamins are fat soluble?

  • Vitamins A, D , E and K are fat soluble vitamins.

Q10. State the difference in the microbes used in secondary and tertiary treatment in sewage treatment.

  • Microbes used in secondary treatment are aerobic microbes while the microbes used in tertiary treatment are anaerobic microbes.

2 Marks Questions

Q1. Match the products with their microbial souce.

  • Ans:
Column – I Column – II
1 Lipase b) Rhizopus sp
2 Erythromycin a) Streptomyces erythreus
3 Gluconic acid d) Aspergillus niger
4 Vitamin B12 c) Pseudomonas denitrificans

Q2 Give the chemical composition of biogas and state two advantages of using biogas.

  • Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity
  • Advantages of Biogas:
  • It is a cheap, safe and renewable source of energy.
  • It can be used for domestic lighting, cooking street lighting and in small-scale industries.
  • It burns with a blue flame without smoke.
  • It does not cause pollution or imbalance in the environment.
  • It can be easily produced, stored, transported and its control of flame is easy.
  • It improves sanitation of the surroundings.

Q3. Who discovered antibiotics? On which bacteria was he working at that time.

  • Alexander Fleming discovered antibiotics.
  • He prepared Penicillin from Penicillium notatum while working with Staphylococcus aureus.

Q4. Name some human diseases that can be controlled by using antibiotics.

  • Many deadly diseases like plague, whooping cough, diphtheria and leprosy can be controlled by using antibiotics.

Q5. Write a note on fungi as a source of food.

  • Mushrooms and truffles belong to Basidiomycetes (fungi) and produce large fleshy fruiting bodies which are edible. They are directly used as a food.
  • They are low calorie, sugar-free, fat-free but rich in proteins, vitamins, minerals, and amino acids.
  • The white button mushroom, paddy straw mushroom, and oyster mushrooms are eatable mushrooms.

Q6. Distinguish between chemical fertilizers and bio-fertilizers.

Chemical Fertilizers


Chemical fertilizers are manufactured artificially. Biofertilizers are microorganisms such as bacteria, fungi etc. that
They are primarily, chemicals having nitrogen, phosphate and potash as main soil nutrients. Biofertilizers are primarily living organisms
They provide micronutrients They fix free nitrogen from the atmosphere, which is then used by the crops.
Chemical fertilizers are the sources of environmental pollution. Biofertilizers have no side effect on soil and environment
e.g: Urea, Ammonium phosphate etc. e.g. Azotobacter, Azospirillum, Rhizobium etc.

Q7. What are weedicides? Give two examples of weedicides.

  • Weedicides are chemicals which are sprayed over a field to get rid of weeds. They do not show any effect on crop plant.
  • Example: 2,4-D Ethyl ester and neem extract, Glyposate

Q8.  Describe the association of Azolla and Anabaena.

  • Some species of Anabaena are symbiotic. (Anabaena azollae). Azolla is an aquatic fern. It propagates vegetatively and spreads in the rice field very rapidly.
  • Anabaena filaments are with heterocyst and they multiply inside the air space of dorsal lobe of leaves of Azolla.

Q9. What are gibberellins? Give its applications.

  • Gibberellins are a group of growth hormones produced by higher plants and fungi to promote growth by stem elongation.
  • Uses of gibberellins:
  • Gibberellins are used to induce parthenocarpy in apple, pear etc.
  • They are also used for breaking dormancy and inducing flowering.

Q10. Enlist the scientist who contributed to

a) discovery of the first antibiotic

  • Dr. Alexander Fleming

b) isolation of gibberellins from rice seedlings:

  • Japanese scientists Yabuta and Sumiki. 

Q11.  Explain the enrichment of soil fertility by using

a)  Rhizobium b) Nostoc


  • Rhizobium is a nitrogen-fixing bacteria found in a symbiotic relation in nodules of dicot plants. Rhizobium fixes atmospheric nitrogen in form of nitrates which is used by the plant. Thus rhizobium acts as biofertilizers.


  • Nostoc is a genus of cyanobacteria found in various environments which is used as biofertilizers. Nostoc fixes atmospheric nitrogen into ammonia, which may then be used or converted to a form suitable for plant growth.

Q12.  Give reason biogas plants are more often built in rural areas.

  • In rural areas, there is a lot of household waste and agricultural waste for the feed and a  lot of space which is the main requirement of a biogas plant.
  • Plant and animal wastes are used as feed to the biogas plant. It is not available in the city area.
  • Biogas plant sludge can be used as a fertilizer in agricultural activities. Hence biogas plants are more often built in rural areas.

Q13. State, whether BOD will be high or low

a)  In water after primary treatment

  • The BOD after primary treatment is high.

b)  In water after secondary treatment.

  • The BOD after secondary treatment is low.
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One Comment

  1. This is useful to me lot of.

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