Class 8 Science Chapter 2 MCQ for 2020-21
| Class: 8 | Science |
| Chapter 2: | MCQ Tests of Microorganism: Friend and Foe |
Class 8 Science Chapter 2 MCQ Tests for Exams
Class 8 Science Chapter 2 MCQ Tests of Microorganism: Friend and Foe with complete explanation and answers. All the questions have four option with one option correct. After attempting you can see the answer and explanation for justification. All the important topics of NCERT Books 8th Science Chapter 2 have been added in these MCQs.
Q1
Paheli wants to know the incorrect statements, given by her teacher as home-work?
[A]. Sodium chloride prevents microbial infection in food.
[B]. Rhizobium may be called beneficial bacteria.
[C]. Vector are the agents for killing the microbes.
[D]. None of the above
Answer: Option C
Explanation:Carrier or vector are the modes of transmission of a disease. Rest of all are correct. Hence, you answer will be option [C].
Q2
Paheli wants to know the non-benefits about microorganisms?
[A]. They can create production of alcohol by fermentation.
[B]. They can create rust of wheat.
[C]. They are caused in cleaning up of the environment.
[D]. None of the above.
Answer: Option B
Explanation:Rust of wheat is caused by fungi which is a disease in plants. Therefore, option [B] is non-benefits of microorganisms.
Q3
Pathogenic microorganisms present in host cells are killed by medicines called
[A]. Pain killer
[B]. Antibodies
[C]. Antibiotics
[D]. Vaccines
Answer: Option C
Explanation:Antibiotics are substances that may inhibit or kill the growth of different microbes. Microorganisms causing infection in host bodies are killed by consumption of these antibiotics.
Q4
A disease “Tetanus” is caused by which bacteria:
[A]. Clostridium tetani
[B]. Vibrio cholerae
[C]. Salmonella typhi
[D]. Mycobacterium tuberculosis
Answer: Option A
Explanation:In 1975 John Bartlett, the discovery of Clostridium difficile and he identified it as the leading cause of hospital-associated infections. Tetanus is caused by a toxin made by spores of bacteria, Clostridium tetani, found in soil, dust and animal feces. When the spores enter a deep flesh wound, they grow into bacteria that can produce a powerful toxin, tetanospasmin. The toxin impairs the nerves that control your muscles (motor neurons).
Q5
The two microorganisms which live in symbiotic association in lichens are
[A]. Fungus and protozoa
[B]. Algae and bacteria
[C]. Bacteria and protozoa
[D]. Algae and fungus
Answer: Option D
Explanation:Lichens is an association between fungal and an algal species. It is a mutually benefiting association where algae provide food to the fungus and in return gets shelter from it.
Q6
Boojho wants to know the preventing method which should not be listed?
[A]. We should make sure that only disposal syringes and needles are used for giving us injection.
[B]. Make sure injections are need to reuse.
[C]. We should avoid to take towels, clothes, bed, utensils used by an infected person.
[D]. All the above
Answer: Option B
Explanation:Healthcare providers (doctors, nurses, and anyone providing injections) should never reuse a needle or syringe either from one patient to another or to withdraw medicine from a vial. Both needle and syringe must be discarded once they have been used.
Q7
In which of the following human disease is or are caused by bacteria?
[A]. Typhoid
[B]. Cholera
[C]. Tuberculosis
[D]. All the above
Answer: Option D
Explanation:Typhoid is a bacterial infection that can lead to a high fever, diarrhea, and vomiting. It can be fatal. It is caused by the bacteria Salmonella typhi. Cholera is an infectious disease that causes severe watery diarrhea, which can lead to dehydration and even death if untreated. It is caused by eating food or drinking water contaminated with a bacterium called Vibrio cholerae.
Tuberculosis (TB) develops when Mycobacterium tuberculosis bacteria are inhaled into the lungs. The infection usually stays in the lungs.
Q8
Malaria is caused by
[A]. Bacteria
[B]. Virus
[C]. Fungus
[D]. None of the above.
Answer: Option D
Explanation:Malaria is not caused by a virus or bacteria. Malaria is caused by a parasite known as Plasmodium, which is normally spread through infected mosquitoes. A mosquito takes a blood meal from an infected human, taking in Plasmodia which are in the blood. Ronald Ross is famous for his work concerning malaria and was awarded the Nobel Prize for Physiology or Medicine in 1902. He discovered that the salivary gland in the mosquito was the storage site of malarial parasites and using infected birds, he demonstrated the full life cycle of the malarial parasitic organism
Q9
The precaution is observed in the use of antibiotics. Choose the incorrect sentence(s):
[A]. Antibiotic may kill the useful bacteria in the body and harm us.
[B]. Wrong dose of antibiotics makes the antibiotic less effective.
[C]. Antibiotics should be taken only on the advice of perfect doctor.
[D]. None of the above
Answer: Option C
Explanation:Antibiotics should be taken only on the advice of “Qualified Doctor”. Qualified doctor means a person who is legally qualified to practice medicine; doctor of medicine. In the other words, a person who engaged in general medical practice, as distinguished from one specializing in surgery.
Q10
A disease “Tetanus” is caused by which bacteria:
[A]. Clostridium tetani
[B]. Vibrio cholerae
[C]. Salmonella typhi
[D]. Mycobacterium tuberculosis
Answer: Option A
Explanation:In 1975 John Bartlett, the discovery of Clostridium difficile and he identified it as the leading cause of hospital-associated infections. Tetanus is caused by a toxin made by spores of bacteria, Clostridium tetani, found in soil, dust and animal feces. When the spores enter a deep flesh wound, they grow into bacteria that can produce a powerful toxin, tetanospasmin. The toxin impairs the nerves that control your muscles (motor neurons).
Types of Fungi
| Yeasts: | Unicellular organisms. |
| Moulds: | Multi cellular organisms. |
| Mushrooms: | Multi cellular organisms. |
| Maldews: | Unicellular organisms. |
The Common Characters of Viruses
- They are the smallest living organisms.
- They do not have a cellular structure.
- They have a simple structure, consisting of a small piece of Nucleic Acid (either DNA or RNA), surrounded by a protein coat.
- They are on the boundary between living and non-living.
Discovery of Viruses
In 1852, a Russian botanist D.I. Ivanovsky discovered viruses from tobacco plants. These viruses were named as TMV (Tabacco Mosaic Viruses). Viruses are the smallest living organisms, ranging in size from about 20-300 mm on average. They cannot be seen with the simple microscope. They pass through filters which retain bacteria.
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What is micro-biology?
There is a world of living organisms which cannot be seen with the naked eyes. They can be seen only through a microscope. Microorganisms are often described as single -celled or unicellular organisms, but there are certain species that are multi-cellulars. The study of micro-organisms is called micro-biology.
What are Extremophiles?
Micro-organisms are found in a variety of places, and they can survive in extremely harsh environmental
conditions. Some types of micro-organisms have adapted to the extreme conditions and sustained colonies; these organisms are known as Extremophiles.
What is Bacteriology?
Becteria are microscopic, unicellualar organisms. They are often coocus -(Spherical) or red-shaped and 0.5- 51/m in the longest dimension. The study of bacteria is known as Bacteriology.
What are Pathogens?
Some micro-organisms are useful to us in many ways, while some are definitely harmful since they cause diseases. The microorganisms which cause disease are known as Pathogens.
