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Class 12 Microbes in Human Welfare worksheet
CBSE Biology. Microbes and their products, sewage treatment and BOD, fermentation yields, biogas, biocontrol. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
Curd is formed from milk by:
- Aspergillus
- Streptococcus only
- yeast
- lactic acid bacteria (Lactobacillus)
Answer
(d) lactic acid bacteria (Lactobacillus)
- 2.
Which microbe is used for cyclosporin A, an immunosuppressant for organ transplants?
- Trichoderma polysporum
- Glomus
- Rhizobium
- Bacillus thuringiensis (Bt)
Answer
(a) Trichoderma polysporum
- 3.
What is Trichoderma polysporum used for?
- Controlling butterfly caterpillars
- Fermenting dough for bread, and ethanol
- Turning milk into curd, which also raises its vitamin B₁₂
- Cyclosporin A, an immunosuppressant for organ transplants
Answer
(d) Cyclosporin A, an immunosuppressant for organ transplants
Section B · short answer
- 4.
How does curd improve the nutritional value of milk?
Answer
Lactic acid bacteria raise the vitamin B₁₂ content, and in our stomach they also help check disease-causing microbes.
- 5.
What is each of these microbes used for: (i) Lactobacillus (lactic acid bacteria); (ii) baculoviruses (Nucleopolyhedrovirus)?
Answer
(i) turning milk into curd, which also raises its vitamin B₁₂; (ii) species-specific control of insect pests
Section C · long answer
- 6.
Describe the treatment of sewage in a sewage treatment plant.
Answer
Primary treatment removes large and small particles: floating debris by sequential filtration and grit by sedimentation; the settled solids form primary sludge. Secondary (biological) treatment: the primary effluent goes to aeration tanks, where air is pumped in and aerobic microbes grow into flocs that consume organic matter, greatly reducing the BOD. In the settling tank the flocs settle as activated sludge; some is returned as inoculum, and the rest is digested anaerobically, producing biogas. The effluent is released into rivers.
Fresh sheets for your child
In the app, every Microbes in Human Welfare sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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