Human Health And Disease Chapter 7 : NCERT Solutions for Class 12

SimplyAcad has provided the best NCERT Solutions of Human Health and Disease Class 12 Chapter 7 exercises prescribed in the textbook. These questions test the knowledge and understanding of the concepts related to the chapter. The answers provided are explained in a detailed manner with simplest language to maintain clarity. 

Our subject experts have formed the answers according to the recent syllabus of 2024-25, this allows students to use the right method for approaching the questions in their paper. Regular practice and revision is a must to boost the confidence in students who will be appearing for the 12th board examination.

Human Health and Disease Class 12 Chapter 7 Question 1 to 4

Question 1

What are the various public health measures, which you would suggest as safeguards against infectious diseases?

Solution:

Public health measures are taken to prevent and control the spread of infectious diseases. These measures include:

• Isolation: Prevents the spread of airborne diseases (e.g., chickenpox, pneumonia, tuberculosis) by isolating the infected person to reduce the chances of disease transmission.
• Vaccination: Protects the body against communicable diseases by administering agents that mimic the microbe, helping to provide passive immunization. Vaccines are available for diseases like mumps, polio, and measles.
• Vector eradication: Prevents diseases such as dengue and malaria by ensuring a clean environment, regulating water to avoid stagnation, using mosquito nets and insecticides, and introducing fish like Gambusia in ponds to control mosquito larvae.
• Public and personal hygiene: Includes maintaining a clean body, consuming healthy and nutritious food, and ensuring clean water. Proper disposal of waste, excreta, and disinfecting water reservoirs are also essential.

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Question 2

In which way has the study of biology helped us to control infectious diseases?

Solution:

Biology has played a crucial role in controlling infectious diseases by:

• Enabling the complete eradication of fatal diseases like smallpox through immunization and vaccines.
• Successfully controlling diseases like diphtheria, polio, and pneumonia with vaccines.
• Facilitating the treatment of infectious diseases with antibiotics and other drugs.

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Question 3

How does the transmission of each of the following diseases take place?

(a) Amoebiasis
(b) Malaria
(c) Ascariasis
(d) Pneumonia

Solution:

Name of the Disease	Transmission
Amoebiasis	Ingestion of cysts of Entamoeba histolytica through contaminated water and food.
Malaria	Transmission of Plasmodium via a bite from an infected female Anopheles mosquito.
Ascariasis	Ingestion of contaminated water and food containing Ascaris eggs.
Pneumonia	Spread through droplets and sputum when an infected person coughs.

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Question 4

What measures would you take to prevent water-borne diseases?

Solution:

Measures to prevent water-borne diseases include:

• Providing clean and safe drinking water.
• Prohibiting industries from discharging waste into water bodies.
• Regular cleaning and disinfecting of water tanks and reservoirs.

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Human Health and Disease Class 12 Chapter 7 Question 4 to 8

Question 5

Discuss with your teacher what ‘a suitable gene’ means in the context of DNA vaccines.

Solution:

The term ‘suitable gene’ refers to a specific section of DNA that can be modified in the host to produce a particular protein that targets and kills a specific disease-causing organism.

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Question 6

Name the primary and secondary lymphoid organs.

Solution:

• Primary lymphoid organs: Thymus and bone marrow.
• Secondary lymphoid organs: Mucosal-associated lymphoid tissues (MALT), lymph nodes, spleen, Peyer’s patches (small intestine).

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Question 7

The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:

(a) MALT
(b) CMI
(c) AIDS
(d) NACO
(e) HIV

Solution:

• (a) MALT – Mucosal-Associated Lymphoid Tissues
• (b) CMI – Cell-Mediated Immunity
• (c) AIDS – Acquired Immuno-Deficiency Syndrome
• (d) NACO – National Aids Control Organization
• (e) HIV – Human Immuno-deficiency Virus

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Question 8

Differentiate the following and give examples of each:

(a) Innate and acquired immunity
(b) Active and passive immunity

Solution:

(a) Innate and acquired immunity

Innate Immunity	Acquired Immunity
Non-specific in nature.	Specific in nature.
Present from birth.	Acquired in response to a particular pathogen.
Involves various barriers.	Has memory of the antibody response.
Example: Mucus traps bacteria.	Example: Post-vaccination antibodies respond to pathogens.

(b) Active and passive immunity

Active Immunity	Passive Immunity
The body produces antibodies in response to pathogens.	Antibodies are introduced directly into the body.
Slower response.	Faster response.
Example: Antibody production after vaccination.	Example: Colostrum, rich in antibodies, is transferred from mother to baby.

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Human Health and Disease Class 12 Chapter 7 Question 9 to 12

Question 9

Draw a well-labelled diagram of an antibody molecule.

Solution:

[Insert Diagram Here]

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Question 10

What are the various routes by which transmission of human immunodeficiency virus takes place?

Solution:

The various routes of HIV transmission are:

• Sexual contact with an infected person.
• Organ transplantation from an infected donor.
• Transfusion of contaminated blood or blood products.
• From mother to child through the placenta during pregnancy.

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Question 11

What is the mechanism by which the AIDS virus causes deficiency of the immune system of the infected person?

Solution:

After entering the body, the AIDS virus (HIV) infects macrophages and helper T-lymphocytes. In macrophages, the RNA genome of the virus is converted into viral DNA by reverse transcriptase. This viral DNA is integrated into the host cell’s DNA, leading to the production of new virus particles. These viruses infect other helper T-lymphocytes, leading to a progressive decrease in the number of these cells, weakening the immune system and resulting in acquired immunodeficiency.

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Question 12

How is a cancerous cell different from a normal cell?

Solution:

Cancerous Cell	Normal Cell
Lack of contact inhibition, leading to uncontrolled division.	Exhibits contact inhibition, stopping division when in contact with other cells.
Does not undergo differentiation.	Undergoes differentiation after growth.
Can invade adjacent tissues and disrupt their function.	Remains confined to a specific location.

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Human Health and Disease Class 12 Chapter 7 Question 13 to 17

Question 13

Explain what is meant by metastasis.

Solution:

Metastasis is the process by which cancerous cells spread from the original (primary) tumor to other parts of the body, forming new (secondary) tumors. These cells break away from the primary tumor, travel through the bloodstream or lymphatic system, and establish new tumors in distant organs or tissues.

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Question 14

List the harmful effects caused by alcohol/drug abuse.

Solution:

Harmful effects of alcohol:

• On individuals: Adverse effects on the nervous system and liver, leading to symptoms like fatigue, depression, aggression, and in extreme cases, heart failure, coma, or death.
• On family: Domestic violence, verbal abuse, and insecurity.
• On society: Impulsive behavior, social withdrawal, and increased violence.

Harmful effects of drugs:

• On individuals: Severe effects on the central nervous system, liver, and kidneys. Increased risk of HIV among drug users due to shared needles. Short-term effects include mood swings and depression.
• On family and society: Issues within the family, antisocial behavior, frustration, and irritation.

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Question 15

Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

Solution:

Yes, friends can influence one to take alcohol or drugs. To protect oneself from such influences:

• Develop strong willpower and avoid experimenting with alcohol/drugs out of curiosity or peer pressure.
• Stay away from people who use drugs or alcohol.
• Seek advice from elders, peers, or medical professionals.
• Educate yourself about the consequences of drug abuse.
• Engage in hobbies or extracurricular activities.
• Seek professional help if feeling depressed or frustrated.

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Question 16

Why is it that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.

Solution:

Alcohol and drug use create an addictive impact associated with euphoria, providing a temporary feeling of well-being. Regular intake increases the body’s tolerance, leading to the need for higher doses to achieve the same effect, making it difficult to quit the habit.

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Question 17

In your view, what motivates youngsters to take to alcohol or drugs and how can this be avoided?

Solution:

Youngsters may be motivated to take alcohol or drugs due to curiosity, excitement, peer pressure, stress, and negative emotions. Media portrayal and unstable family relationships also contribute. To avoid this:

• Encourage strong willpower and educate them about the risks.
• Parents should monitor their children’s social circles and guide them away from negative influences.
• Promote involvement in positive activities and hobbies.
• Provide professional help if needed, and create awareness about the dangers of substance abuse.