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Glance on Biology Chapter 7 Human Health and Diseases Class 12 NCERT Solutions
Detailed explanations for human health and diseases NCERT Solutions and a free PDF packed with clear concepts are provided.
The 12th biology 7th chapter exercise will give you a basic idea about the chapter. It will help the students understand human health, diseases, and other important related terms.
The chapter consists of theories on diseases causing pathogens and agents. It will give a clear idea of how the pathogens use an infected human body as a host to resume a part of their lifecycle.
Students will get to learn what pathogens are and how they damage critical parts of human physiology. The concepts of immunity, AIDS, cancer, and drug and alcohol issues in society are also covered in the NCERT Solutions of Class 7 Biology Human Health and Disease.
In Human Health and Diseases Class 12 NCERT solutions, students will get all the answers to all the questions given in the chapter exercise, which will help them learn the chapter systematically.
1. What are the various public health measures you would suggest as a safeguard against infectious diseases?
Ans: Public health measures are preventive measures that are taken to check the spread of various infectious diseases. These measures should be taken to reduce contact with infectious agents. Some of these methods are:
(1) Personal and Public Hygiene Should be Maintained: One of the most important methods of preventing infectious diseases is the maintenance of personal and public hygiene. Personal hygiene involves maintaining a clean body, consumption of healthy and nutritious food, drinking clean water, etc. Whereas public hygiene involves proper disposal of waste material, excreta, periodic cleaning, and disinfection of water reservoirs.
(2) Isolation of Infected Persons: To prevent the spread of air-borne diseases such as pneumonia, chickenpox, tuberculosis, etc., it is essential to keep the infected person in isolation to reduce the chances of spreading these diseases.
(3) Vaccination: The protection of the body from communicable diseases by administering some agent that mimics the microbe inside the body is known as vaccination. It provides both active and passive immunization to the body. Various vaccines are available for the treatment of many diseases such as tetanus, polio, measles, mumps, etc.
(4) Vector Eradication: Many diseases such as malaria, filariasis, dengue, and chikungunya spread through vectors. By providing a clean environment and preventing the breeding of mosquitoes these diseases can be prevented easily. By not allowing water to stagnate around residential areas, the breeding of mosquitoes can be prevented. To keep our environment healthy, regular cleaning of coolers should be done, also the use of mosquito nets, and insecticides such as malathion in drains, ponds, etc. should be considered. Fish such as Gambusia are introduced in ponds to control the breeding of mosquito larvae in stagnant water.
2. In which way has the study of biology helped us to control infectious diseases?
Ans: In the field of biology, various advancements once a person starts taking alcohol or drugs have helped us in gaining a better understanding to fight against various infectious diseases. Biology has helped us in studying the life cycle of various parasites, pathogens, and vectors along with their modes of transmission and controlling measures. Vaccination programs against several infectious diseases such as smallpox, chickenpox, tuberculosis, etc. have helped nearly eradicate these diseases. In the preparation of newer or safer drugs and vaccines, biotechnology has helped a lot. In treating infectious diseases the antibiotics have also played a very important role.
3. How does the transmission of each of the following diseases take place?
(a) Amoebiasis
(b) Malaria
(c) Ascariasis
(d) Pneumonia
Ans:
4. What measure would you take to prevent water-borne diseases?
Ans: Water-borne diseases like cholera, typhoid, hepatitis B, etc. spread by drinking contaminated water. By ensuring proper disposal of sewage, excreta, and periodic cleaning habits we can prevent ourselves from water-borne diseases. Along with these, measures such as disinfecting community water reservoirs, boiling and filtering drinking water, etc. should also be observed.
5. Discuss with your teacher what ‘a suitable gene’ means, in the context of DNA vaccines.
Ans: In the context of DNA vaccines, a ‘suitable gene’ refers to a specific DNA segment that can be injected into the cells of the host body to produce specific proteins. The specific proteins kill the specific disease-causing organism in the body of the host and it also provides immunity to the host body.
6. Name the primary and secondary lymphoid organs.
Ans: The names of primary and secondary lymphoid organs are as follows:
(a) Primary lymphoid organs - The bone marrow and the thymus.
(b) Secondary lymphoid organs - The spleen, lymph nodes, tonsils, Peyer’s patches of the small intestine, and appendix.
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
Ans: The abbreviations with their full forms are as follows:
(a) MALT – Mucosa – Associated Lymphoid Tissue
(b) CMI – Cell-Mediated Immunity
(c) AIDS – Acquired Immunodeficiency Syndrome
(d) NACO – National AIDS control organization
(e) HIV – Human Immunodeficiency Virus
8. Differentiate the following and give examples of each:
(a) Innate and acquired immunity
Ans:
(b) Active and passive immunity
Ans:
9. Draw a well-labelled diagram of an antibody molecule.
Ans: A well-labelled diagram of an antibody molecule is drawn below.
In diagram
(a) Antigen binding site
(b) Light chain
(c) Disulphide bridges
(d) Constant region
(e) Heavy chain
(f) Variable region of light chain
(g) Constant region of light chain
(h) Disulphide bonds
10. What are the various routes by which transmission of the human immunodeficiency virus takes place?
Ans: AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). The various modes of transmission of this virus are:
Making unprotected sexual contact with an infected person.
Transfusion of an infected person’s blood to a healthy person.
Sharing of infected needles and syringes.
Through the placenta from an infected mother to a child.
11. What is the mechanism by which the AIDS virus causes deficiency of the immune system of the infected person?
Ans: AIDS (Acquired Immunodeficiency Syndrome) is caused by the human immunodeficiency virus (HIV) through sexual or blood-blood contact. After entering the human body, HIV attacks and enters the macrophages. The RNA of the virus replicates with the help of enzyme reverse transcriptase and gives rise to viral DNA, inside the macrophages. After this, the viral DNA is incorporated into the host DNA and directs the synthesis of virus particles. Simultaneously, HIV enters into the helper T-lymphocytes. There it replicates and produces viral progeny. Now, these newly formed progeny viruses get released into the blood, attacking other healthy helper T lymphocytes in the body. As a result, the number of T-lymphocytes in the body of an infected person decreases progressively and hence decreases the immunity of a person.
12. How is a cancerous cell different from a normal cell?
Ans: The differences are given below in the table.
13. Explain what is meant by metastasis.
Ans: Metastasis Property is exhibited by malignant tumours. and it is the pathological process of spreading cancerous cells to the different parts of the body. These cells divide uncontrollably, forming a mass of cells called tumours. From the tumour, some cells get sloughed off and enter into the bloodstream. Through the bloodstream, these cells reach different parts of the body, and therefore, by dividing actively at their position they begin the formation of new tumours
14. List the harmful effects caused by alcohol/drug abuse.
Ans: Alcohol and drugs have several adverse effects on the individual, his family, and society. The list of harmful effects is given below:
(A) Effects of alcohol:
(a) Effects on the Individual: Alcohol harms the body of an individual. The consumption of excess alcohol by an individual causes damage to the liver and the nervous system. This results in the appearance of other symptoms such as depression, fatigue, aggression, loss of weight, and appetite in the individual. Sometimes, extreme levels of alcohol consumption may also lead to heart failure, resulting in coma and death. Also, pregnant women should avoid alcohol as it may inhibit the normal growth of the baby.
(b) Effects on the Family:
Consumption of excess alcohol by any family member is having devastating effects on the family. It may lead to several domestic problems such as quarrels, frustrations, insecurity, etc.
(c) Effects on Society:
(i) Rash behavior
(ii) Malicious mischief and violence
(iii) Deteriorating social network
(iv) Loss of interest in social and other activities
(B) Effects of Drugs: An individual who is addicted to using drugs can create several problems not only for himself but also for his family too.
Effects on the Individual: Drugs harm the central nervous system of an individual which results in the malfunctioning of several other organs of the body such as the kidney, liver, etc. In these individuals, the spread of HIV is most common because they share common needles while injecting drugs into their bodies. On both males and females drugs have long-term side effects which include increased aggressiveness, mood swings, and depression.
Effects on the Family and Society: A person addicted to drugs creates problems for his family and society too. That person becomes frustrated, irritated, and anti-social.
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?
Ans: Yes, I think that friends can highly influence a person to take drugs or alcohol. Following steps should be taken by a person for protecting himself/herself against drug abuse:
(a) Increase your willpower to stay away from alcohol and drugs. For curiosity and fun, one should not experiment with alcohol.
(b) Avoid the company of drug-taking friends.
(c) Seek help from parents and peers.
(d) Take proper knowledge and counseling about drug abuse and devote your energy to other extracurricular activities.
(e) If symptoms of depression and frustration become apparent, seek immediate professional and medical help from psychologists and psychiatrists.
16. Why is it that it is difficult to get rid of this habit once a person starts taking alcohol or drugs? Discuss it with your teacher.
Ans: Drug and alcohol consumption has an inherent addictive nature related to euphoria and a short-lived feeling of well-being. Repeated intake of medicine increases the tolerance level of the body’s receptors, resulting in more consumption of medicine.
17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
Ans: Many factors are liable for motivating youngsters towards alcohol or drugs. The initial causes of motivation are curiosity, the need for adventure and excitement, experimentation. Some youngsters start consuming drugs and alcohol to beat negative emotions (such as stress, pressure, depression, frustration) and to excel in various fields. Several mediums like television, the internet, newspaper, movies, etc. are also responsible for promoting the idea of using alcohol for fun to the younger generation. Among these factors, reasons such as unstable and unsupportive family structures and peer pressure can also lead an individual to depend on drugs and alcohol. Preventive measures that work against addiction to alcohol and drugs too are given below:
(a) Parents should motivate and try to increase the willpower of their children.
(b) Parents should educate their children regarding the ill effects of alcohol. They should provide them with proper knowledge and counselling regarding the consequences of addiction to alcohol.
(c) It’s the responsibility of the parent to discourage a toddler from experimenting with alcohol. Youngsters should be kept far away from the company of friends who consume drugs.
(d) Children should be encouraged to devote their energy to other extra-curricular and recreational activities.
(e) Proper professional and medical help should be provided to the child if sudden symptoms and depression and frustration are observed.
Topics Covered in Class 12 Chapter 7: Human Health and Diseases
Benefits of Learning With Human Health and Diseases Class 12 NCERT Solutions
The Human Health and Diseases class 12 NCERT will help the students to learn and understand the chapter thoroughly. Here are some of the key features of studying the 12th biology 7th chapter exercise.
Detailed explanations and step-by-step solutions for all topics in the chapter.
Includes topics like common diseases in humans, immunity, AIDS, cancer, drugs, and alcohol abuse.
NCERT Solutions for Human Health and Diseases Class 12 is curated by experienced educators to ensure accuracy and clarity.
Covers important concepts such as the immune system, types of immunity, and the role of pathogens in diseases.
Clear and concise explanations using precise biological terminology.
Detailed analysis of the causes, symptoms, and prevention of various diseases.
Aligned with the latest CBSE syllabus and exam pattern.
In-depth analysis of key concepts and their applications in real-life scenarios.
Detailed explanation of topics like the lifecycle of the malarial parasite, cancer and its types, and the effects of drugs and alcohol on the human body.
Important Study Materials For Chapter 7- Human Health and Diseases
Conclusion
The human health and diseases class 12 NCERT solutions provide an invaluable resource for students studying the topic in-depth. The 12th biology 7th chapter exercise covers all the questions related to the chapter. The solutions provide accurate answers and offer additional explanations, examples, and relevant diagrams to facilitate better comprehension of the subject matter and effectively prepare students for board exams.
NCERT Solutions for Class 12 Biology | Other Chapter-wise Links
The other chapter-wise links for NCERT Solutions for Class 12 Biology are given below.
Other Related Links for Class 12 Biology
FAQs on CBSE Class 12 Biology Chapter 7 Human Health and Disease – NCERT Solutions 2025–26
1. How do the NCERT solutions for Class 12 Biology Chapter 7 explain the public health measures needed to prevent infectious diseases?
The NCERT solutions for Class 12 Biology, Chapter 7, detail several essential public health measures for disease prevention. The correct approach for an exam answer includes these points:
- Maintenance of Personal and Public Hygiene: This involves keeping the body clean, consuming uncontaminated food and water, proper disposal of waste and excreta, and regular disinfection of public water reservoirs.
- Isolation of Infected Persons: To prevent the spread of highly contagious airborne diseases like pneumonia and chickenpox, it is critical to keep infected individuals separate from healthy ones.
- Vaccination Programs: Administering vaccines to build immunity against severe diseases such as polio, tetanus, and measles is a cornerstone of public health.
- Vector Control: Eradicating disease-carrying organisms (vectors) like mosquitoes is crucial. This is achieved by preventing water stagnation, using insecticides, and introducing biological controls like Gambusia fish in ponds.
2. What is the correct method to explain how the study of biology has helped control infectious diseases, as per the NCERT exercise?
According to the NCERT solutions, a complete answer should highlight how biology has provided the tools to fight diseases. Key points to include are:
- Understanding the life cycles of pathogens and vectors, which allows us to identify and break their transmission chains.
- The development of effective vaccines against diseases like smallpox and tuberculosis, which has helped in their near-eradication.
- Advancements in biotechnology that have led to the creation of new, safer, and more effective drugs and vaccines.
- The discovery and mass production of antibiotics, which have been fundamental in treating bacterial infections successfully.
3. How should one answer the question on the transmission modes of Amoebiasis, Malaria, Ascariasis, and Pneumonia for the CBSE exam?
For a full-marks answer, the NCERT solutions indicate the need for precise transmission modes for each disease:
- Amoebiasis: Transmitted through the faecal-oral route. The primary source is consuming food or water contaminated with the cysts of the protozoan parasite Entamoeba histolytica.
- Malaria: Spreads to humans through the bite of an infected female Anopheles mosquito, which acts as a vector to transfer the Plasmodium sporozoites.
- Ascariasis: Caused by ingesting food or water that has been contaminated with the eggs of the common roundworm, Ascaris lumbricoides.
- Pneumonia: Spreads directly from person to person by inhaling infectious droplets or aerosols released when an infected individual coughs or sneezes.
4. The NCERT solutions list primary and secondary lymphoid organs. Why is this distinction important for understanding the immune system?
This distinction is crucial because the two types of organs perform different, sequential functions in the immune response. Primary lymphoid organs, which are the bone marrow and thymus, are the sites where lymphocytes (B-cells and T-cells) originate and mature. It is here they learn to recognise 'self' from 'non-self'. In contrast, secondary lymphoid organs, such as the spleen, lymph nodes, and tonsils, are the sites where mature lymphocytes encounter antigens and initiate the adaptive immune response. Without primary organs, there would be no functional lymphocytes to carry out surveillance in the secondary organs.
5. What are the full forms of MALT, CMI, AIDS, NACO, and HIV as required in the solutions for Chapter 7?
The NCERT textbook for Chapter 7 requires students to know the full forms of these key abbreviations. The correct expansions are:
- MALT: Mucosa-Associated Lymphoid Tissue
- CMI: Cell-Mediated Immunity
- AIDS: Acquired Immunodeficiency Syndrome
- NACO: National AIDS Control Organisation
- HIV: Human Immunodeficiency Virus
6. When solving the NCERT question on the difference between innate and acquired immunity, what key concepts must be included for a high-scoring answer?
To provide a comprehensive solution as per the CBSE pattern, you must compare innate and acquired immunity on several key parameters:
- Specificity: Innate immunity is non-specific and acts against all pathogens, while acquired immunity is pathogen-specific.
- Timing: Innate immunity is present from birth. Acquired immunity develops only after the body is exposed to a specific pathogen or through vaccination.
- Memory: Innate immunity lacks immunological memory. Acquired immunity is characterised by memory, which allows for a faster and more intense response upon subsequent infection with the same pathogen.
- Components: Innate immunity involves physical barriers (skin, mucus), physiological barriers (fever), and cells like neutrophils. Acquired immunity relies on B-lymphocytes and T-lymphocytes.
7. According to the NCERT solutions, what is the step-by-step mechanism by which the HIV virus weakens the human immune system?
The solution outlines a precise sequence of events:
- After entering the body, the HIV virus first targets and enters cells like macrophages.
- Inside the macrophage, the viral RNA is converted into viral DNA by the enzyme reverse transcriptase.
- This viral DNA is then incorporated into the host cell's DNA, forcing the cell to produce new virus particles. The macrophage effectively becomes an 'HIV factory'.
- Simultaneously, HIV infects and destroys helper T-lymphocytes, which are crucial for coordinating the immune response.
- The progressive destruction of these T-cells leads to a severely weakened immune system, making the person highly vulnerable to other infections.
8. Why is 'metastasis' considered a defining feature of malignant tumours but not benign tumours in the NCERT solution?
The NCERT solution explains that metastasis is the property that makes malignant tumours so dangerous. Malignant tumour cells lose the property of contact inhibition, allowing them to divide uncontrollably. They can break away from the primary tumour, travel through the bloodstream or lymphatic system, and establish new tumours in other parts of the body. This process of spreading is called metastasis. In contrast, benign tumours are non-cancerous and remain encapsulated at their original site; they do not invade other tissues and hence do not show metastasis.
9. What steps does the NCERT solution suggest to protect oneself from peer pressure related to alcohol or drug use?
The solution provides a clear, step-by-step guide for self-protection against such influences:
- Develop strong willpower and make a firm decision to avoid experimenting with harmful substances.
- Carefully choose friends and avoid the company of individuals who indulge in alcohol or drug abuse.
- Do not hesitate to seek help and guidance from trusted adults like parents and teachers.
- Gain proper knowledge about the severe consequences of addiction and channel energy into positive outlets like sports, hobbies, or studies.
- If experiencing symptoms of stress or depression, seek professional medical help immediately.
10. The NCERT exercise asks why quitting alcohol or drugs is so difficult. What is the biological reason for this, based on the chapter's concepts?
The difficulty in quitting is due to the biological phenomena of addiction and dependence. Drugs and alcohol stimulate the brain to release chemicals like dopamine, which creates a powerful but temporary feeling of pleasure or euphoria. With repeated use, the brain's receptors adapt and become less sensitive, a condition known as tolerance. This forces the individual to consume larger amounts to achieve the same effect. Over time, the body becomes physically dependent on the substance for normal functioning. When the substance is withdrawn, the person experiences severe and unpleasant withdrawal symptoms, making it extremely difficult to quit without proper support and medical intervention.
