Class 8 Science - Microorganisms Friend or Foe HOTS Questions

1. The yeast multiply by a process called

(a)    Binary fission

(b)   Budding

(c)    Spore formation

(d)   None of the above

Ans: b

2. The example of protozoan is

(a)    Penicillium

(b)   Blue green algae

(c)    Amoeba

(d)   Bacillus

Ans: c

3. The most common carrier of communicable diseases is

(a)    Ant

(b)   Housefly

(c)    Dragonfly

(d)   Spider

Ans: b
The housefly is the most common carrier of communicable diseases. Here are some key points:

• Houseflies can carry harmful pathogens from waste to food.
• They often land on contaminated surfaces, picking up germs.
• When they touch uncovered food, they can transfer these germs, leading to illness.
• To prevent disease, always cover food and maintain good hygiene.

Housefly

4. The following is an antibiotics

(a)    Alcohol

(b)   Yeast

(c)    Sodium bicarbonate

(d)   Streptomycin

Ans: d

5. Yeast produces alcohol and carbon dioxide by a process called

(a)   Evaporation

(b)   Respiration

(c)   Fermentation

(d)   Digestion

Ans: c
Yeast produces alcohol and carbon dioxide through a process called fermentation. This process involves:

• Conversion of sugar into alcohol.
• Release of carbon dioxide, which helps dough rise in baking.
• Utilisation of natural sugars found in grains and fruits.

Fermentation is crucial in the production of various foods and beverages, including bread and wine.

6. The algae commonly used as fertilizers are called

(a)   Staphylococcus

(b)   Diatoms

(c)   Blue green algae

(d)   None of the above

Ans: c
Blue-green algae, also known as cyanobacteria, are commonly used as fertilizers due to their ability to:

• Fix nitrogen from the atmosphere.
• Enhance soil fertility.
• Support plant growth by providing essential nutrients.

These algae play a vital role in agriculture and are beneficial for sustainable farming practices.

7. Cholera is caused by

(a)   Bacteria

(b)   Virus

(c)   Protozoa

(d)   Fungi

Ans: a

• Cholera is caused by bacteria.
• These bacteria are known as Vibrio cholerae.
• Cholera is primarily transmitted through contaminated water or food.

8. Plant disease citrus canker is caused by

(a)   Virus

(b)   Fungi

(c)   Bacteria

(d)   None of these

Ans: c

9. The bread dough rises because of

(a)   Kneading

(b)   Heat

(c)   Grinding

(d)   Growth of yeast cells

Ans: d

• The bread dough rises due to the growth of yeast cells.
• Yeast ferments the sugars in the dough.
• This process produces carbon dioxide, which creates bubbles.
• These bubbles expand, causing the dough to rise.

Q 10.  Carrier of dengue virus is

(a)   House fly

(b)   Dragon fly

(c)   Female Aedes Mosquito

(d)   Butterfly

Ans: c
The carrier of the dengue virus is the female Aedes mosquito. This mosquito is responsible for transmitting the virus to humans through its bites.

• The dengue virus is not spread by common insects like houseflies or butterflies.
• It is crucial to control the population of Aedes mosquitoes to prevent dengue outbreaks.

Q 11.  Yeast is used in the production of

(a)   Sugar

(b)   Alcohol

(c)   Hydrochloric acid

(d)   Oxygen

Ans: b
Alcohol Yeast is primarily used in the production of:

• Alcohol - Yeast ferments sugars to produce alcohol.
• Other options like sugar, hydrochloric acid, and oxygen are not produced by yeast.

Q 12.  The vaccine for smallpox was discovered by

(a)    Robert Koch

(b)   Alexander Fleming

(c)    Sir Ronald Ross

(d)   Edward Jenner

Ans: d
Edward Jenner is credited with the discovery of the smallpox vaccine in 1798. His work laid the foundation for modern vaccination practices. Here are some key points about his contribution:

• Jenner used material from cowpox lesions to create immunity against smallpox.
• This method demonstrated that exposure to a related, less harmful virus could protect against a more dangerous one.
• His discovery significantly reduced the incidence of smallpox, leading to its eventual eradication.

Q 13. Chickenpox is caused by

(a)    Virus

(b)   Fungi

(c)   Protozoa

(d)   Bacteria

Ans: a

• Chickenpox is caused by a virus.
• It spreads through air or direct contact with an infected person.
• Common symptoms include itchy rashes and fever.

Q 14. The bacterium which promote the formation of curd

(a)   Rhizobium

(b)   Spirogyra

(c)   Breadmould

(d)   Lactobacillus

Ans: d
The bacterium that helps in making curd is Lactobacillus. Here are some key points:

• Lactobacillus is a type of bacteria.
• It multiplies in warm milk, turning it into curd.
• This process is essential for making various dairy products.

Q 15. Plasmodium is a human parasite which causes

(a)   dysentery

(b)  Sleeping sickness

(c)   Malaria

(d)   All of the above

Ans: c

• Plasmodium is a type of protozoan parasite.
• It is responsible for causing malaria in humans.
• Malaria is transmitted through the bite of infected female Anopheles mosquitoes.
• Symptoms of malaria include fever, chills, and flu-like illness.

Thus, the correct answer is C) Malaria.

Q 16. The bacterium Bacillus Anthracis was discovered by

(a)   Edward Jenner

(b)   Alexander Fleming

(c)   Louis Pasteur

(d)   Robert Koch

Ans: d
Robert Koch Robert Koch discovered the bacterium Bacillus anthracis, which causes anthrax disease. His work was crucial in understanding how this bacterium affects both humans and animals.

Q 17. Carrier of malaria causing protozoan is

(a)   Butterfly

(b)   Housefly

(c)   Female Anopheles Mosquito

(d)   Cockroach

Ans: c
The carrier of the malaria-causing protozoan is the female Anopheles mosquito. Here are some key points:

• Malaria is caused by a parasite called Plasmodium.
• The female Anopheles mosquito is essential for transmitting this parasite.
• Other insects, like houseflies and cockroaches, do not transmit malaria.

Q 18. The process of conversion of sugar into alcohol is called

(a)   Infection

(b)   Moulding

(c)   Nitrogen fixation

(d)   Fermentation

Ans: d

Q 19. Foot and mouth disease of cattle is caused by

(a)   Fungi

(b)   Virus

(c)    Algae

(d)   None of these

Ans: b
Virus Foot and mouth disease in cattle is caused by a virus. This highly contagious viral infection affects cloven-hoofed animals, leading to:

• Blisters in the mouth and on the feet
• Fever and drooling
• Loss of appetite and weight

Effective control measures include:

• Vaccination of livestock
• Quarantine of infected animals
• Strict hygiene practices on farms

Q 20. Which of the following is not a fungi

(a)    Paramecium

(b)   Bread mould

(c)    Penicillium

(d)   Aspergillus  

Ans: a

• The organism that is not a fungus is A) Paramecium.
• Paramecium is a type of protozoan, which is different from fungi.
• Fungi include organisms like bread mould, Penicillium, and Aspergillus.