NCERT Solutions for Class 12 Biology Chapter 7 Human Health and Disease
NCERT Solutions for Class 12 Biology Chapter 7 Human Health and Disease covers Common Infectious Diseases in Humans, Immunity (Innate and Acquired), Vaccination, Allergy, Autoimmunity, AIDS, Cancer, and Drug and Alcohol Abuse.
Overview of Topics & Subtopics (Click to Jump)
1. Common Diseases in Humans & Immunity
Short Note:
• Common Pathogens & Diseases:
- Typhoid: Caused by Salmonella typhi (confirmed by Widal Test).
- Pneumonia: Caused by Streptococcus pneumoniae or Haemophilus influenzae.
- Malaria: Caused by Plasmodium (P. vivax, P. falciparum, P. malariae). Vector: Female Anopheles mosquito. Malignant malaria caused by P. falciparum is fatal.
- Amoebiasis: Caused by Entamoeba histolytica.
- Ringworms: Caused by fungi belonging to genera Microsporum, Trichophyton, Epidermophyton.
• Immunity Types:
1. Innate Immunity: Non-specific defense present from birth (Physical, Physiological, Cellular, and Cytokine barriers like Interferons).
2. Acquired Immunity: Pathogen-specific defense characterized by memory. Involves B-lymphocytes (produce antibodies) and T-lymphocytes (help B-cells and provide Cell-Mediated Immunity/CMI).
2. AIDS, Cancer & Autoimmune Disorders
Short Note:
• AIDS (Acquired Immuno Deficiency Syndrome): Caused by Human Immunodeficiency Virus (HIV), a retrovirus with RNA genome. Targets Helper T-cells (TH cells), leading to severe loss of immunity. Diagnosed by ELISA test.
• Cancer: Uncontrolled mitotic cell division resulting in formation of masses of cells called tumors (Benign and Malignant). Malignant tumors show Metastasis (sloughed off cells reach new sites via blood and start new tumors).
- Causes: Carcinogens (Physical: X-rays/UV; Chemical: Tobacco smoke; Biological: Oncogenic viruses).
• Autoimmunity: Abnormal immune response where body attacks its own self-cells (e.g., Rheumatoid arthritis).
3. Drugs and Alcohol Abuse
Short Note:
• Opioids: Bind to opioid receptors in CNS and GI tract. E.g., Morphine (extracted from latex of Papaver somniferum / Opium poppy), Heroin (Diacetylmorphine / Smack, depressant).
• Cannabinoids: Obtained from Cannabis sativa. Affect cardiovascular system (Marijuana, Hashish, Charas, Ganja).
• Coca Alkaloids / Cocaine: Obtained from Erythroxylum coca. Interferes with neurotransmitter Dopamine; acts as a potent CNS stimulant causing euphoria and hallucinations.
• Addiction & Dependence: Psychological attachment to certain effects like euphoria and temporary feeling of well-being. Withdrawal symptoms occur if regular dosage is abruptly discontinued.
Intext & Conceptual Questions
| Feature | Innate Immunity | Acquired Immunity |
|---|---|---|
| Presence | Present right from birth. | Acquired during lifetime after exposure to pathogens. |
| Specificity | Non-specific type of defense. | Pathogen-specific type of defense. |
| Memory | No immunological memory. | Characterized by immunological memory. |
| Components | Physical, physiological, cellular, and cytokine barriers. | B-lymphocytes (humoral) and T-lymphocytes (cell-mediated). |
Metastasis: It is the property of malignant tumor cells to detach from the primary tumor site, migrate via blood or lymph to distant organs, and establish secondary tumors in new locations.
Why feared: Metastasis makes cancer treatment extremely difficult because tumor cells spread throughout the body, leading to multi-organ failure and rapid health deterioration.
Textbook Chapter End Exercise Questions
The life cycle of Plasmodium requires two hosts:
1. Human Host (Asexual Phase):
• Female Anopheles mosquito injects sporozoites into human blood through bite.
• Sporozoites reach liver cells via blood and multiply asexually, rupturing liver cells.
• Parasites enter Red Blood Cells (RBCs) and reproduce asexually, causing RBCs to burst.
• Rupture of RBCs releases toxic substance Haemozoin, responsible for recurring high fever and chills every 3-4 days.
• Sexual stages (gametocytes) develop in RBCs.
2. Mosquito Host (Sexual Phase):
• Mosquito takes up gametocytes with blood meal.
• Fertilization and development occur in mosquito's gut.
• Mature infective sporozoites migrate to mosquito's salivary glands, ready to infect a new human host.
• Primary Lymphoid Organs: Organs where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
Examples: Bone Marrow and Thymus.
• Secondary Lymphoid Organs: Organs where differentiated lymphocytes interact with antigens and proliferate to form effector cells.
Examples: Spleen, Lymph nodes, Tonsils, Peyer's patches of small intestine, and MALT.
| Drug | Source Plant | Health Effect / Hazard |
|---|---|---|
| Heroin | Papaver somniferum (Opium poppy) | Acts as a depressant and slows down bodily functions; highly addictive. |
| Cannabinoids | Cannabis sativa (Hemp plant) | Affects cardiovascular system and alters perception/mood. |
| Cocaine | Erythroxylum coca | Stimulates central nervous system, produces euphoria, and induces severe hallucinations at high doses. |
Read More & Chapter Resources
These short notes are designed for quick revision. Read the main points once, then use the related material below to practise the same chapter. Revising a concept and checking it with questions can make your preparation more focused.