Ncert solution for class 8 science ch 2 microorganism friend and foe.


ncert solution of class 8 science ch 2.


 These NCERT solutions for science 8 include detailed answers to all questions in Chapter 2 - micro-organisms provided in the NCERT book, Friends and Enemies who are scheduled for Class 8 in schools Are there.
science book
book

questions 1 to 5.

Q 1. Fill in the blanks.
Answer:
(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria

Q 2. Tick the correct option.
Answer:
(a) alcohol
(b) streptomycin
(c) female anopheies mosquito
(d) housefly
(e) growth if yeast cells
(f) fermentation

Q 3
Match the following column I and II.
Answer:
           Column I                           column II 
(i) Bacteria ------------------ causing cholera
(ii) Rhizobium-------------- fixing nitrogen
(iii) Lactobaccilus--------- setting of curd
(iv) Yeast----------------------- baking of bread
(v) A protozoan------------- causing malaria
(vi) A virus-------------------- causing AIDS

Q 4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: Micro organisms can be seen through the naked eye. They can be seen with the help of a magnifying glass or microscope.
For example, the fungus growing on the bread is so small that it can only be seen with the help of a magnifying glass or microscope.

Q 5What are the major groups of microorganisms?
Answer: There are five major groups of micro-organisms:
(i) Bacteria - they are a cell-patient-micro organisms. They can be spiral or rod-shaped.
(ii) Fungi - they are mostly microscopic micro-organisms. Bread mold are common examples of fungi.
(iii) Protozoa - They primarily contain organisms such as amoeba, plasmodium, etc.
They can be unicellular or multicellular.
(iv) Virus-virus are micro-organisms that produce disease, which are reproduced only within the host organism.

(v) Algae - They include multicellular, photosynthetic organisms such as spirogyra, clamidodona etc.

questions 6 to 9.

Q 6.Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer: Bacteria such as rhizobium in the soil and some blue-green algae can cure atmospheric nitrogen and convert it into usable nitrogenous compounds. These nitrogenous compounds can be easily used by plants for the synthesis of plant proteins and other compounds.

Q 7.Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Micro organisms can be seen through the naked eye. However, they are important for plants and the environment.
Importance of micro-organisms:
They are used in the process of making winemaking, baking, pickling and other food.
Fermentation of alcohol by yeast is widely used in the preparation of alcohol and bread.
A bacterial lactobacillus promotes the formation of yogurt.
Microorganisms are used to reduce pollution. For example, disruptions like bacteria and fungi break the dead body and emit to form arctic compounds, which can be absorbed by plants.
They are used to help improve soil fertility by fixing atmospheric nitrogen with the help of bacteria Rhizobium and some other blue-green algae.
Microbial also plays an important role in the preparation of medicines. Antibiotics contain chemicals produced by microorganisms to kill bacteria. Streptomycin, for example, is an antibiotic.
Some microorganisms are also used in biological treatment of sewage and industrial pollution.

Q 8.Write a short paragraph on the harms caused by microorganisms.
Answer: Harmful effects of micro-organisms:
Microorganisms cause diseases in animals. For example, in humans, bacteria causes illnesses such as tuberculosis, cholera, typhoid etc. In cattle, foot and mouth disease is caused by a virus. Apart from this, many microorganisms cause diseases in plants. For example, due to microbial diseases in plants, the productivity of wheat, orange, apple etc. decreases. On entering our body some microorganisms produce toxic substances. This leads to food poisoning. Some micro-organisms like fungus spoil our food. For example, under the salted conditions on bread, unutilized bread produces a white cotton-like increase on the bread.

Q 9. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer: Antibiotics medicines produce some micro-organisms to kill micro-organisms. These medicines are usually obtained from bacteria and fungi. Streptomycin, tetracycline, penicillin, etc. are common antibiotics.
Caution should be taken while using antibiotics:
(i) Antibiotics should be taken under the supervision of a qualified doctor.
(ii) The course (intake) of antibiotics should be completed according to the prescription given by the doctor.
(iii) Antibiotics should be taken in the right amount and at the right time. An incorrect dose of antibiotics makes the drug ineffective. In addition, excessive consumption of medicines can kill useful bacteria present in our body.


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