NCERT Solutions for Class 12 Biology Chapter 8 Human Health and Disease in Hindi Mediem
FAQs on NCERT Solutions for Class 12 Biology In Hindi Chapter 8 Human Health and Disease In Hindi Mediem
1. How should you explain the transmission methods of common infectious diseases like Amoebiasis and Pneumonia in your NCERT solutions for Class 12 Biology?
When preparing the NCERT solution for Chapter 8, explain the transmission of diseases by identifying the causative agent and the mode of transmission.
- Amoebiasis: Caused by the protozoan Entamoeba histolytica. Its transmission occurs through the faecal-oral route. The primary source is contaminated food and water, with houseflies acting as mechanical carriers.
- Pneumonia: Caused by bacteria like Streptococcus pneumoniae. It is transmitted when a healthy person inhales droplets or aerosols released by an infected person during coughing or sneezing. Sharing utensils with an infected person can also spread the disease.
2. What is the correct method to differentiate between Innate and Acquired Immunity as per the NCERT Class 12 syllabus?
To correctly differentiate between these two types of immunity for your NCERT solution, you should create a comparison based on key characteristics:
- Origin: Innate immunity is present from birth (inborn), while acquired immunity develops during an individual's lifetime after exposure to a pathogen.
- Specificity: Innate immunity is non-specific, providing a general defence against all pathogens. Acquired immunity is pathogen-specific.
- Memory: Innate immunity does not have immunological memory. Acquired immunity is based on memory; a second encounter with the same pathogen elicits a stronger, faster response.
- Components: Innate immunity includes physical barriers (skin), physiological barriers (stomach acid), cellular barriers (phagocytes), and cytokine barriers. Acquired immunity involves B-lymphocytes and T-lymphocytes.
3. How can you provide a step-by-step solution for the mechanism by which HIV depletes the immune system?
For a complete NCERT solution, explain the mechanism of HIV action in a sequential manner:
1. Entry: The HIV virus enters the host body and infects macrophages, which act as an 'HIV factory'.
2. Replication: Inside the macrophage, the viral RNA genome replicates to form viral DNA using the enzyme reverse transcriptase.
3. Integration: This viral DNA incorporates into the host cell's DNA and directs the infected cell to produce new virus particles.
4. Attack on T-cells: The newly produced viruses are released and attack helper T-lymphocytes (TH cells).
5. Immune Depletion: This cycle repeats, leading to a progressive decrease in the number of helper T-cells. Since TH cells are critical for the immune system, their depletion severely compromises the body's ability to fight off even minor infections, leading to Acquired Immunodeficiency Syndrome (AIDS).
4. Why is the loss of 'contact inhibition' a crucial point to include when explaining the difference between a cancer cell and a normal cell in NCERT solutions?
Including 'contact inhibition' is crucial because it is the fundamental property that distinguishes the growth patterns of normal and cancerous cells. A complete solution should state that normal cells exhibit contact inhibition, a mechanism that stops cell growth and division upon contact with other cells. In contrast, cancer cells lose this property. This loss allows them to grow in an uncontrolled and unregulated manner, invading adjacent tissues and forming tumours. Mentioning this concept demonstrates a deeper understanding of the mechanism behind oncogenic transformation.
5. How does the study of biology help in controlling infectious diseases, as required for the NCERT Class 12 exercise?
The study of biology provides the essential knowledge to control infectious diseases in several ways:
- Pathogen Identification: It helps identify the causative agents (like bacteria, viruses, fungi) of various diseases.
- Understanding Life Cycles: By studying the life cycles of pathogens and vectors (e.g., mosquito in malaria), we can identify weak points to break the chain of transmission.
- Developing Treatments: Knowledge of pathogen biology is fundamental to developing effective antibiotics and other drugs.
- Vaccine Production: Understanding the immune response (immunology) allows for the creation of vaccines that provide active immunity against specific diseases.
6. What are the key public health measures that should be listed in the NCERT solution for preventing infectious diseases?
Your NCERT solution should list the following key public health measures:
- Education: Spreading awareness about personal and community hygiene.
- Sanitation: Proper disposal of waste and excreta to prevent contamination.
- Clean Food and Water: Ensuring access to safe drinking water and uncontaminated food.
- Vector Control: Eradicating or controlling disease vectors like mosquitoes by draining stagnant water and using insecticides.
- Vaccination: Implementing large-scale immunisation programs to protect the population against diseases like polio, measles, and tetanus.
7. How should you structure the answer for the NCERT question on the harmful effects of alcohol and drug abuse?
To structure this answer effectively, categorize the harmful effects into immediate and long-term consequences:
- Immediate Effects: Include reckless behaviour, vandalism, and violence. High doses can lead to coma or death due to respiratory or heart failure.
- Long-term Health Effects: Mention chronic use leading to damage to the nervous system and liver cirrhosis (from alcohol). Using drugs intravenously can transmit serious infections like HIV (AIDS) and Hepatitis B.
- Social and Mental Effects: Note that addiction can lead to social isolation, depression, poor academic performance, and financial distress for the individual and their family.
8. What is the biological reason it is difficult to stop alcohol or drug use once someone starts, a key concept in Chapter 8?
The difficulty in quitting stems from the concepts of tolerance and dependence. Your answer should explain that with repeated use, the receptors in our brain adapt and their tolerance level increases. This means the person needs progressively larger doses to achieve the same effect. This leads to a state of psychological and physical dependence, where the body shows characteristic and unpleasant withdrawal symptoms if the drug or alcohol is discontinued. This withdrawal syndrome forces the user to continue the cycle of abuse to avoid discomfort.
9. How do you list the primary and secondary lymphoid organs for the NCERT solution?
The solution should clearly distinguish between the two types of lymphoid organs based on their function.
1. Primary Lymphoid Organs: These are the organs where immature lymphocytes differentiate into antigen-sensitive lymphocytes. They include:
- Bone marrow
- Thymus
2. Secondary Lymphoid Organs: These organs provide the sites for lymphocytes to interact with antigens and proliferate to become effector cells. They include:
- Spleen
- Lymph nodes
- Tonsils
- Peyer's patches of the small intestine

















