Chhattisgarh Board Class 8 Science Chapter 8 Solution

Chhattisgarh Board Class 8 Science Chapter 8 Solution

 

CG Board Class 8 Micro Organisms –A Wonderful World

 

Choose the correct alternative:-

 

Thing which cannot be seen by naked eyes are of the size –

• Smaller than 1 micron
• Smaller than 10 micron
• Smaller than 100 micron
• Smaller than 1000 micron

 

The first person to see micro organisms by observing bacteria through the self made microscope was –

• Robert Hooke
• Antonia Leewan Hawk
• Edward Jenner
• Louis Pasteur.

 

The germs causing malaria is –

• Bacteria
• Virus
• Protozoa
• Fungi

 

The micro-organisms present in the roots of bengal gram is –

• Bacteria
• Virus
• Protozoa
• Fungi

 

Mushroom is a ………………..

• Protozoa
• Algae
• Flower
• Fungi

 

HIV/AIDS is caused due to –

• Bacteria
• Virus
• Protozoa
• Fungi

 

Answer the following question in short :-

 

(1)     How does boot polish protect leather shoes?

Boot polish protects leather shoes by forming a protective layer on the surface of the leather, which helps repel water, dust, and other things.

 

(2)     Why does curd sometimes turn bitter?

Curd sometimes turns bitter due to the overgrowth of certain bacteria strains, such as Lactobacillus lactis or Lactobacillus fermentum, which produce lactic acid and other compounds that contribute to the bitter taste.

 

(3)     Why must the milk be lukewarm when curd is to be made from it?

Milk must be lukewarm when making curd because it provides an optimal temperature range (around 40-45°C) for the growth and activity of the bacteria cultures present in the curd starter, allowing them to ferment the milk and convert it into curd

 

(4)     How does the leguminous plants increase the fertility of the soil?

Leguminous plants increase the fertility of the soil by hosting nitrogen-fixing bacteria, such as Rhizobium, in their root nodules. These bacteria convert atmospheric nitrogen into a form that can be utilized by plants, thereby enriching the soil with nitrogenous compounds essential for plant growth.

 

(5)     Why must we safe guard food items from micro organisms?

We must safeguard food items from microorganisms to prevent food spoilage, contamination, and the spread of foodborne illnesses caused by harmful bacteria, fungi, viruses, and other pathogens present in the environment.

 

(6)     What are the medium through which micro organisms enter our body?

Microorganisms can enter our body through various mediums, including contaminated water, food, air, direct contact with infected individuals, vectors such as mosquitoes or ticks, and contact with contaminated surfaces or objects.

 

(7)     Must we use the handkerchief used by a person suffering from cold and fever or not? Explain with reasons.

No, we should not use the handkerchief used by a person suffering from cold and fever because it may contain infectious microorganisms like viruses or bacteria that can be transmitted to others and cause illness.

 

(8)     What happens, when our body looses its resistance power?

When our body loses its resistance power, it becomes more susceptible to infections and illnesses caused by microorganisms. This can lead to increased frequency and severity of infections, prolonged recovery times, and overall compromised health.

 

(9)     Why is cleanliness necessary for being healthy?

Cleanliness is necessary for being healthy because it helps prevent the spread of harmful microorganisms that can cause diseases and infections. Maintaining personal hygiene, clean surroundings, and proper sanitation practices reduce the risk of microbial contamination and promote overall health and well-being.

 

(10)   What will happen if a small amount of curd is added to milk to prepare curd and then heated.

If a small amount of curd is added to milk to prepare curd and then heated, the heat will kill the live bacterial cultures present in the curd starter, preventing the milk from fermenting and turning into curd effectively.

 

(11)   Why do the doctors advice us to drink boiled water ?

Doctors advise drinking boiled water to ensure its safety by killing or inactivating harmful microorganisms, such as bacteria, viruses, and parasites, that may be present in untreated water. Boiling water is an effective method of water purification that reduces the risk of waterborne diseases.

 

Important Points

Microorganisms, which cannot be seen by the naked eye, are typically smaller than 100 microns.

Antoni van Leeuwenhoek was the first person to observe microorganisms, including bacteria, through microscopes he made himself.

The germs causing malaria are protozoa of the genus Plasmodium.

Mushroom belongs to the kingdom Fungi.

HIV/AIDS is caused by the human immunodeficiency virus (HIV), which is a type of virus.