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Science Answer the following questions: [2 M]

Cell Structure and Micro-organisms · Maharashtra Board STD 7 (MSBSHSE - English Medium). 11 questions.

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Answer the following questions: [2 M]

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11 questions · timed · auto-graded

Question 12 Marks
How do micro-organism survive the adverse conditions?
Answer
  1. During adverse conditions micro-organisms form a thick covering around themselves and stop their life processes.
  2. On return of favourable conditions they come out of the protective covering and continue their life processes.
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Question 22 Marks
Why should dry and wet waste be collected separately?
Answer
  1. Dry waste consist of plastic, glass, metals, paper, etc. It is easier to segregate dry waste so that it is easier for treatment and recycling of waste.
  2. Wet waste consists of organic matter. Wet garbage is converted into manure of the best quality and surroundings are kept clean.
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Question 32 Marks
What are the needs of cells?
Answer
  1. The most important things for a cell are oxygen and glucose.
  2. Cell uses these during process of glycolysis and makes ATP which is energy source.
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Question 42 Marks
What precautions will you take while purchasing food? Why?
Answer
  1. We will see the expiry date. If the food is kept for a long period of time, it may allow the growth of many microbes which can cause disease or food poisoning.
  2. We will check for any fungal growth, any white or black spots on it.
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Question 52 Marks
How will you know that a foodstuff is spoilt?
Answer
  1. When the food is kept for a long time it allows the growth of bacteria and fungi.
  2. We can see the white layer of bacterial or fungal growth on it, it causes a typical odour, or smell, and also the food tastes sour due to presence of enterotoxins produced by fungi in the food.
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Question 62 Marks
Who discovered the process of fermentation?
Answer
  1. Louis Pasteur established that fermentation is initiated by living organisms.
  2. It involves yeast microbes, breaking down molecules of complex carbohydrates into simple sugar, alcohol and $CO_2$.
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Question 72 Marks
What does your mother do to make yoghurt from milk?
Answer
  1. Few drops of yoghurt or buttermilk are mixed with lukewarm milk and it is kept at room temperature for 8-10 hours.
  2. Microbes present in the drops of yoghurt quickly multiply and the milk gets converted into yoghurt. This is a process of fermentation.
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Question 82 Marks
What is the powdery material found on old currency notes or old rubber or paper?
Answer
  1. The powdery material is the spores of fungi.
  2. All the materials like gunny bags, cotton clothes, paper, rubber, etc. are plant products and leather is an animal product.
  3. In a humid atmosphere, fungi and some other micro-organisms grow on these articles and spoil or damage them.
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Question 92 Marks
Why are leather articles like purses, wallets, belts, footwear always polished before storing away?
Answer
They are polished so as to protect them from the growth of fungus.
  1. Polish creates a layer of wax on them so that moisture cannot enter from atmosphere.
  2. It prevents the growth of fungus, which damages the leather.
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Question 102 Marks
Observe the roots of the pea, bean and fenugreek plants. What could be the functions of the nodules on their roots.
Answer
  1. Micro-organisms are present in the root nodules.
  2. They fix the atmospheric nitrogen and make it available for plants.
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Question 112 Marks
When will you use a simple microscope and when a compound microscope?
Answer
  1. I will use a simple microscope to magnify the objects and to see the growth of a fungi or mucor on a piece of moist bread.
  2. I will use a compound microscope in Research Laboratory and high school science lab to observe micro-organisms which we are not able to see with our naked eye.
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Answer the following questions: [2 M] - Science STD 7 Questions - Vidyadip