Microorganisms Friend and Foe is a chapter in class 8 science book. This chapter discusses the microorganisms present around us. In this chapter we talk about different microbes like bacteria, virus, fungi, bacteria and protozoans etc Below we have shared the NCERT book solutions for Microorganisms Friend and Foe chapter
Question 1: Fill in the blanks:
(a) Microorganisms can be seen with the help of a_microscope__.
(b) Blue-green algae fix _nitrogen_ directly from, air to enhance fertility of the soil.
Question 2: Tick the correct answer from the following:
(a) Yeast is used in the production of
(i) sugar
(ii) alcohol
(iii) hydrochloric acid
(iv) oxygen.
Ans Alcohol
(b) The following is an antibiotic
(i) sodium bicarbonate
(ii) streptomycin
(iii) alcohol
(iv) yeast.
Ans: Streptomycin
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly.
Ans: female Anopheles mosquito
(d) The most common carrier of communicable diseases is
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider
Ans: housefly
e) The bread or idli dough rises because of
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading.
Ans: growth of yeast cells
(f) The process of conversion of sugar into alcohol is called
Ans: Fermentation
Question 3:
Match the organisms in Column A with corresponding ones in Column B.
Column A
Column B
(i) Bacteria
(a) Fixing nitrogen
(ii) Rhizobium
(b) Setting of curd
(iii) Lactobacillus
(c) Baking of bread
(iv) Yeast
(d) Causing malaria
(v) A protozoan
(e) Causing cholera
(vi) A virus
(f) Causing AIDS
Blank
(g) Producing antibodies
Ans:
(i) Bacteria: Causing Cholera disease
(ii) Rhizobium: Nitrogen fixation
(iii) Lactobacillus: Setting of curd
(iv) Yeast: Baking of the bread
(v) A protozoan: Causing malaria
(vi) A virus: Causing AIDS
Question 4: Can microorganisms be seen with the naked eyes? If not how can they be seen?
Ans 4: No, microorganisms can not be seen by naked eyes because they are very very small in size. We need to use a microscope in order to see them clearly. Microscope lens can be adjusted to focus more clearly.
Question 5: What are the major groups of microorganisms?
Ans: Microorganisms can be divided into fungi, bacteria, protozoans. algae and viruses. Each type has its own characteristics.
Question 6: Name the microorganisms which can fix atmospheric nitrogen in the soil.
Ans: Rhizobium is a bacteria which help to fix the atmospheric nitrogen into the soil
Question 7: Write 10 points on the usefulness of microorganisms in our lives.
Ans. Let us check how our microorganisms are useful in our lives:-
Yeast is used in the formation of bread
Lactobacillus helps in the preparation of curd
Microorganisms provide nutrition to the soil which beneficial for heterotrophs.
Medicines are made by using some microorganisms.
They also help to keep the environment clean
They help in the decomposition of substances
They also help in the formation of manure which is good for plants
Vinegar can be made by using yeast which is useful in edible items
Food preservatives make use of microorganisms so that the food can sustain for a long period of time.
Question 8: Write a short paragraph on the harms caused by microorganisms.
Ans 8: Microorganisms may cause harm to humans and animals. They are the cause for various diseases present in humans. Some of the diseases caused by these microorganisms are typhoid, Whooping cough caused by bacterium, bubonic plague, TB (Tuberculosis), Malaria caused by a protozoan, etc They may cause food poisoning. You may have also suffered from poisoning after eating from unhygienic places. They can decompose certain food items. Bread, fruits etc
Question 9: What are antibiotics? What precautions must be taken while using antibiotics?
Ans 9: Antibiotics as the name suggest, something which acts against the biotic substances: i.e the microorganisms produced in our body. These are the medicines which act against the virus, bacteria, and other disease-causing microbes. Antibiotics are prescribed by medical practitioners.
We need to be careful while taking antibiotics because if taken without correct prescription they may cause allergy or other side effects on the body. Some people take antibiotics without consulting doctors. This can be harmful for their health. We should always consult the doctor and should timely take the medicines.
So, these were Class 8 NCERT science solutions for chapter 2. Microorganisms friend and foe. Hope you found them useful. This was Deepak Kumar here. Don’t forget to share these solutions with your classmates and friends 🙂 You can follow us on Facebook to get free ebooks and PDFs.
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