Human Health and Disease
Welcome to HSLC Guru! This page provides complete English-medium notes, summary, question answers, MCQs, fill in the blanks, true/false and a glossary for Class 12 Biology Chapter 8 — Human Health and Disease, prepared strictly according to the ASSEB (Assam State School Education Board) syllabus. The chapter covers concept of health, common human diseases, immunity, vaccination, AIDS, cancer, and drug/alcohol abuse — each topic broken down with clear explanations, diagrams in words, and exam-style answers.
Summary
Concept of Health: Health is a state of complete physical, mental and social well-being, not merely the absence of disease (as defined by WHO). Good health is maintained by balanced diet, personal hygiene, regular exercise, awareness about diseases and their effects on the body, vaccination/immunisation against infectious diseases, proper disposal of wastes, control of vectors and maintenance of clean environment. When the functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms, we say that we are not healthy — that is, we have a disease. Diseases are broadly grouped into infectious (transmitted from one person to another) and non-infectious (e.g., cancer, diabetes).
Common Human Diseases: (a) Bacterial — Typhoid caused by Salmonella typhi (transmitted through contaminated food and water); symptoms include sustained high fever (39–40 °C), weakness, stomach pain, constipation, headache and loss of appetite — confirmed by the Widal test. Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae, infecting the alveoli which fill with fluid causing breathing trouble. (b) Viral — Common cold caused by Rhino viruses, infects the nose and respiratory passage; symptoms — nasal congestion, sore throat, cough, headache. (c) Protozoan — Malaria caused by Plasmodium (P. vivax, P. malariae, P. falciparum), transmitted by the bite of female Anopheles mosquito; Amoebiasis (amoebic dysentery) caused by Entamoeba histolytica, transmitted through contaminated food/water by housefly as mechanical vector. (d) Helminthic — Ascariasis caused by Ascaris lumbricoides (intestinal roundworm); Filariasis (elephantiasis) caused by Wuchereria bancrofti and W. malayi, transmitted by female Culex mosquito. (e) Fungal — Ringworm caused by Microsporum, Trichophyton and Epidermophyton — appears as dry, scaly lesions on skin, scalp, nails, accompanied by itching.
Immunity: The overall ability of the host to fight disease-causing organisms is called immunity. It is of two types — Innate immunity (non-specific, present from birth) provides four types of barriers: Physical barriers (skin, mucous lining of respiratory, digestive and urogenital tracts), Physiological barriers (acid in stomach, saliva, tears in eyes), Cellular barriers (PMNL-neutrophils, monocytes, NK cells, macrophages), and Cytokine barriers (interferons released by virus-infected cells protect non-infected cells). Acquired immunity is pathogen-specific — characterised by memory; primary response is low-intensity at first encounter, subsequent encounters cause heightened secondary/anamnestic response. It is mediated by lymphocytes — B-lymphocytes produce antibodies (humoral immune response, HI) and T-lymphocytes directly attack pathogens (cell-mediated immune response, CMI); CMI is also responsible for graft rejection. Antibodies are proteins of the form H₂L₂ (two heavy + two light chains) — five classes: IgA, IgM, IgE, IgD, IgG. Active immunity is produced by host’s own cells (slow, long-lasting); passive immunity is ready-made antibodies given to the host (e.g., colostrum, antitoxin). Vaccination/immunisation works on the principle of memory — antigenic proteins (vaccines) generate primary response and memory cells, which on subsequent infection produce a massive secondary response. Allergy is the exaggerated response of the immune system to certain antigens (allergens — dust, pollen, mites) producing IgE antibodies; symptoms include sneezing, watery eyes, running nose. Auto-immunity is the condition in which the body attacks self-cells (e.g., rheumatoid arthritis).
AIDS, Cancer and Drug Abuse: AIDS (Acquired Immuno Deficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus), a retrovirus with RNA genome. Transmission — sexual contact with infected person, transfusion of contaminated blood, sharing of infected needles, from infected mother to child through placenta. HIV attacks helper T-cells (TH), reverse transcriptase produces viral DNA which integrates into host DNA — leading to drastic decrease in TH count and immune failure. Diagnosis is by ELISA; treatment uses anti-retroviral drugs. Prevention — safe sex, use of disposable needles, screening of blood. Cancer is uncontrolled proliferation of cells without differentiation — types: Carcinoma (epithelial cells), Sarcoma (connective tissues — bone, muscle), Leukaemia (blood cancer), Lymphoma (lymph nodes/spleen). Causes — physical, chemical and biological carcinogens; oncogenes/proto-oncogenes in normal cells when activated cause cancer. Detection — biopsy, histopathology, MRI, CT, antibodies against tumour-specific antigens. Treatment — surgery, radiotherapy, chemotherapy and immunotherapy (α-interferon). Drugs and Alcohol Abuse: Common drugs of abuse are opioids (heroin/smack, derived from Papaver somniferum) — depresses CNS; cannabinoids (marijuana, hashish, ganja, charas — from Cannabis sativa) — affect cardiovascular system; cocaine (coke/crack from Erythroxylum coca) — potent CNS stimulant; amphetamines, barbiturates — sedatives. Addiction and dependence develop. Prevention — avoid undue peer pressure, education and counselling, seeking help from parents and peers, looking for danger signs, professional and medical help.
Question Answers — 1 Mark
The following short questions are aimed at quick revision of important keywords, scientific names and definitions. Each carries one mark.
Q1. Define health according to WHO.
Answer: Health is a state of complete physical, mental and social well-being and not merely the absence of disease.
Q2. Name the bacterium that causes typhoid.
Answer: Salmonella typhi.
Q3. Which test is used to confirm typhoid?
Answer: The Widal test.
Q4. Name the vector responsible for the transmission of malaria.
Answer: Female Anopheles mosquito.
Q5. Which fungi cause ringworm?
Answer: Microsporum, Trichophyton and Epidermophyton.
Q6. Expand AIDS.
Answer: Acquired Immuno Deficiency Syndrome.
Q7. Name the type of virus that causes AIDS.
Answer: Human Immunodeficiency Virus (HIV) — a retrovirus.
Q8. What is the structural formula of an antibody molecule?
Answer: H₂L₂ — two heavy chains and two light chains.
Q9. Name any two cannabinoid-yielding plants.
Answer: Cannabis sativa (marijuana, hashish, ganja, charas).
Q10. What is the source of cocaine?
Answer: Erythroxylum coca (coca plant).
Q11. Name the protozoan that causes amoebic dysentery.
Answer: Entamoeba histolytica.
Q12. Which immunoglobulin is the most abundant in human blood?
Answer: IgG.
Q13. Name a disease that develops due to over-activation of the immune system against self-antigens.
Answer: Rheumatoid arthritis (an example of auto-immune disease).
Question Answers — 2/3 Marks
The following questions cover comparison-type, definition-type and short-explanation answers. Each carries 2 or 3 marks.
Q1. Distinguish between innate and acquired immunity.
Answer: Innate immunity is non-specific, present from birth and provides four types of barriers (physical, physiological, cellular, cytokine). Acquired immunity is pathogen-specific, develops after exposure to a pathogen, has memory and gives stronger secondary response on re-infection.
Q2. Differentiate between active and passive immunity.
Answer: Active immunity is produced when the host’s own cells generate antibodies in response to antigens (vaccination, infection); it is slow but long-lasting. Passive immunity involves transfer of ready-made antibodies (e.g., colostrum, antitoxin); it acts immediately but is short-lived.
Q3. What is meant by humoral and cell-mediated immune responses?
Answer: Humoral immune response (HI) is mediated by B-lymphocytes which produce antibodies in the blood. Cell-mediated immune response (CMI) is mediated by T-lymphocytes which directly attack pathogens and infected cells; CMI is also responsible for graft rejection.
Q4. List the four barriers of innate immunity with one example each.
Answer: (i) Physical barriers — skin and mucous membranes; (ii) Physiological barriers — HCl in stomach, saliva, tears; (iii) Cellular barriers — neutrophils, monocytes, NK cells, macrophages; (iv) Cytokine barriers — interferons released by virus-infected cells protect non-infected cells.
Q5. Mention the modes of transmission of HIV.
Answer: (i) Sexual contact with an infected person; (ii) transfusion of contaminated blood and blood products; (iii) sharing of infected needles (drug abusers); (iv) from infected mother to child through the placenta.
Q6. What are oncogenes? How are they related to cancer?
Answer: Oncogenes are cancer-causing genes. Their inactive form, called proto-oncogenes, is present in normal cells. Under conditions of activation by physical, chemical or biological carcinogens, they transform normal cells into cancerous (tumour) cells.
Q7. Define addiction and dependence in the context of drug abuse.
Answer: Addiction is a psychological attachment to certain effects (euphoria, temporary feeling of well-being) associated with drugs/alcohol; the user feels a strong urge to use them again and again. Dependence is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome (anxiety, shakiness, nausea, sweating) if regular dose is discontinued.
Q8. Mention any three differences between benign and malignant tumours.
Answer: (i) Benign tumours remain confined to the original location whereas malignant tumours invade and damage surrounding tissues. (ii) Benign tumours grow slowly; malignant tumours grow rapidly. (iii) Cells of malignant tumours travel via blood to distant sites and form new tumours, a property called metastasis; benign tumours do not show metastasis.
Question Answers — 5/7 Marks
The following long-answer questions are intended for descriptive writing — students should attempt them in detail with proper headings, subheadings and labelled diagrams wherever possible.
Q1. Describe the structure of an antibody molecule and name the five classes of antibodies with their functions.
Answer: An antibody (immunoglobulin) is a Y-shaped protein molecule consisting of four polypeptide chains — two identical heavy (H) chains and two identical light (L) chains held together by disulphide bonds. Hence its structure is represented as H₂L₂. Each chain has a variable region (antigen-binding site) and a constant region. The five classes are: IgA — present in mucosal secretions (tears, saliva, colostrum), provides local immunity; IgM — first antibody produced during primary response, large pentameric structure; IgE — involved in allergic reactions and parasitic infections; IgD — present on B-cell surface as antigen receptor; IgG — most abundant in blood, crosses placenta giving passive immunity to the foetus, important in secondary immune response.
Q2. Discuss AIDS — its causative agent, mode of transmission, mechanism of damage to immune system, diagnosis, treatment and prevention.
Answer: AIDS (Acquired Immuno Deficiency Syndrome) was first reported in 1981 and is caused by Human Immunodeficiency Virus (HIV), a retrovirus with single-stranded RNA enclosed in a protein coat. Transmission — (i) sexual contact, (ii) transfusion of contaminated blood, (iii) sharing of infected needles, (iv) infected mother to foetus via placenta. Mechanism — after entering the body, HIV enters macrophages where its RNA replicates by reverse transcriptase to form viral DNA which integrates into host DNA. The infected macrophages release new viruses that attack helper T-lymphocytes (TH); the number of TH cells decreases progressively, weakening immunity and leaving the patient prone to bacterial, viral and protozoan infections. Diagnosis — by ELISA test. Treatment — anti-retroviral drugs (only partially effective). Prevention — making blood safe from HIV, use of disposable needles and syringes in hospitals, free distribution of condoms, control of drug abuse, advocating safe sex, regular check-ups and education through agencies like NACO and WHO.
Q3. Explain cancer — its types, causes, methods of detection and treatment.
Answer: Cancer is a disease characterised by uncontrolled, unregulated proliferation of cells (loss of contact inhibition) leading to formation of a mass called tumour. Tumours are benign (confined to original location) or malignant (invasive, spread by metastasis). Types — (i) Carcinoma — cancers of epithelial tissues (skin, lung, breast); (ii) Sarcoma — cancers of connective tissues like bone and muscle; (iii) Leukaemia — blood cancer (cancer of WBCs in bone marrow); (iv) Lymphoma — cancer of lymph nodes/spleen. Causes — physical carcinogens (X-rays, gamma rays, UV rays), chemical carcinogens (tobacco smoke), biological carcinogens (oncogenic viruses with viral oncogenes); proto-oncogenes/cellular oncogenes get activated. Detection — biopsy and histopathological studies, blood and bone-marrow tests for leukaemia, radiography (X-ray), CT (computed tomography), MRI (magnetic resonance imaging), monoclonal antibodies against tumour-specific antigens. Treatment — (i) Surgery — removal of tumour; (ii) Radiotherapy — irradiation of tumour cells lethally; (iii) Chemotherapy — drugs to kill cancerous cells (most have side effects like hair loss, anaemia); (iv) Immunotherapy — biological response modifiers such as α-interferon activate the immune system to destroy tumour.
Q4. Write an essay on drugs and alcohol abuse — types of commonly abused drugs, adverse effects and prevention.
Answer: Drug abuse is the use of drugs for purposes other than medicinal in amounts and frequencies that impair physical, physiological or psychological functioning. Commonly abused drugs include — Opioids: heroin (smack) — chemically diacetylmorphine, white, odourless, bitter, obtained from latex of poppy plant Papaver somniferum; taken by snorting and injection; depresses the CNS, slows body functions. Cannabinoids: marijuana, hashish, charas and ganja — obtained from inflorescence of Cannabis sativa; affect the cardiovascular system. Cocaine: from Erythroxylum coca; potent CNS stimulant — produces a sense of euphoria and high energy; excessive doses cause hallucinations. Other drugs include amphetamines, barbiturates, benzodiazepines (sedatives) and certain plant products like Atropa belladonna and Datura (hallucinogens). Tobacco contains nicotine which raises blood pressure and heart rate; chronic use causes cancer of lung, urinary bladder and throat, bronchitis, gastric ulcer, etc. Alcohol abuse damages the liver, nervous system, and disrupts family/social life. Repeated use leads to addiction (psychological attachment) and dependence (tendency of the body to manifest withdrawal syndrome). Prevention — (i) avoid undue peer pressure; (ii) education and counselling to face stress and failure; (iii) seeking help from parents and peers; (iv) looking for danger signs such as drop in academic performance, isolation, fatigue; (v) seeking professional and medical help.
Q5. What is vaccination? Explain the principle of immunisation with an example, and distinguish between active and passive immunisation.
Answer: Vaccination/immunisation is the process of introducing a vaccine — antigenic proteins of a pathogen or weakened/inactivated pathogen — into the body to develop immunity against that pathogen. The principle is based on the property of memory of the immune system. On first exposure, the antigens of the vaccine produce antibodies (primary response) and generate memory B and T cells. When the actual pathogen attacks later, these memory cells recognise it quickly and mount a massive secondary (anamnestic) response, neutralising the pathogen. Examples — vaccines against polio, tetanus, hepatitis-B, BCG (tuberculosis). In passive immunisation (e.g., snake-bite anti-venom, tetanus antitoxin), preformed antibodies are directly injected to provide quick relief. In active immunisation, the host’s own immune system produces antibodies in response to the antigens — slower, but provides long-lasting immunity through memory cells. Recombinant DNA technology has enabled large-scale production of safe vaccines such as the hepatitis-B vaccine produced from yeast.
Multiple Choice Questions (MCQs)
Choose the correct option in each of the following questions. These MCQs cover the most important facts of the chapter and are designed for objective-type tests.
Q1. Typhoid is caused by:
(a) Salmonella typhi (b) Streptococcus (c) Plasmodium (d) Rhino virus
Answer: (a) Salmonella typhi.
Q2. Widal test is used for diagnosis of:
(a) Malaria (b) Pneumonia (c) Typhoid (d) AIDS
Answer: (c) Typhoid.
Q3. Malaria is transmitted by the bite of:
(a) Female Culex (b) Female Anopheles (c) Female Aedes (d) Housefly
Answer: (b) Female Anopheles.
Q4. Filariasis is caused by:
(a) Ascaris lumbricoides (b) Wuchereria bancrofti (c) Entamoeba (d) Trichophyton
Answer: (b) Wuchereria bancrofti.
Q5. Antibodies are made up of how many polypeptide chains?
(a) 2 (b) 3 (c) 4 (d) 5
Answer: (c) 4 (two heavy + two light).
Q6. Cell-mediated immunity is provided by:
(a) B-lymphocytes (b) T-lymphocytes (c) Eosinophils (d) Erythrocytes
Answer: (b) T-lymphocytes.
Q7. HIV is a:
(a) DNA virus (b) Bacteriophage (c) Retrovirus (d) Bacterium
Answer: (c) Retrovirus.
Q8. Cancer of epithelial cells is called:
(a) Sarcoma (b) Carcinoma (c) Leukaemia (d) Lymphoma
Answer: (b) Carcinoma.
Q9. Heroin is obtained from:
(a) Cannabis sativa (b) Erythroxylum coca (c) Papaver somniferum (d) Atropa belladonna
Answer: (c) Papaver somniferum.
Q10. Interferons are released by:
(a) Normal cells (b) Virus-infected cells (c) Bacteria (d) Fungi
Answer: (b) Virus-infected cells.
Q11. Acid in the stomach is an example of:
(a) Physical barrier (b) Physiological barrier (c) Cellular barrier (d) Cytokine barrier
Answer: (b) Physiological barrier.
Q12. The vector of filariasis is:
(a) Female Anopheles (b) Female Culex (c) Female Aedes (d) Sandfly
Answer: (b) Female Culex.
Fill in the Blanks
1. The causative agent of amoebiasis is __________.
Answer: Entamoeba histolytica.
2. Antibodies belonging to the class __________ are responsible for allergic reactions.
Answer: IgE.
3. The diagnostic test for AIDS is __________.
Answer: ELISA.
4. Cancer of bone or muscle is known as __________.
Answer: Sarcoma.
5. Cocaine is obtained from the plant __________.
Answer: Erythroxylum coca.
True / False
1. Innate immunity is pathogen-specific. — False (it is non-specific).
2. Colostrum provides passive immunity to the newborn. — True.
3. HIV destroys helper T-lymphocytes. — True.
4. Marijuana is obtained from Papaver somniferum. — False (from Cannabis sativa).
5. α-Interferon is used in immunotherapy of cancer. — True.
Quick Revision Points
- Health is more than absence of disease — it is physical, mental and social well-being.
- Typhoid — Salmonella typhi; confirmed by Widal test; transmitted by contaminated food/water.
- Pneumonia — Streptococcus pneumoniae; affects alveoli of the lung.
- Common cold — Rhino viruses; affects the upper respiratory tract.
- Malaria — Plasmodium (P. vivax, P. malariae, P. falciparum); vector — female Anopheles.
- Amoebiasis — Entamoeba histolytica; mechanical vector — housefly.
- Ascariasis — Ascaris lumbricoides; intestinal roundworm.
- Filariasis — Wuchereria bancrofti; vector — female Culex; causes elephantiasis.
- Ringworm — Microsporum, Trichophyton, Epidermophyton; fungal disease of skin/nails.
- Innate immunity — four barriers: physical, physiological, cellular, cytokine.
- Acquired immunity — primary and secondary response; memory cells; B and T lymphocytes.
- Antibody structure — H₂L₂; classes — IgA, IgM, IgE, IgD, IgG.
- Active immunity is slow but long-lasting; passive immunity is immediate but short-lived.
- AIDS — HIV (retrovirus); attacks helper T-cells; diagnosed by ELISA.
- Cancer types — carcinoma, sarcoma, leukaemia, lymphoma; treatment — surgery, radiotherapy, chemotherapy, immunotherapy (α-interferon).
- Drugs of abuse — opioids (heroin from Papaver somniferum), cannabinoids (from Cannabis sativa), cocaine (from Erythroxylum coca), amphetamines.
- Prevention of drug abuse — avoid peer pressure, education, parental support, professional help.
Glossary
| Term | Meaning |
|---|---|
| Health | State of complete physical, mental and social well-being. |
| Pathogen | Disease-causing organism (bacterium, virus, protozoan, fungus, helminth). |
| Typhoid | Bacterial disease caused by Salmonella typhi; confirmed by Widal test. |
| Pneumonia | Bacterial infection of alveoli caused by Streptococcus pneumoniae. |
| Common cold | Viral infection caused by Rhino viruses affecting nose and respiratory tract. |
| Malaria | Protozoan disease caused by Plasmodium; vector — female Anopheles. |
| Amoebiasis | Amoebic dysentery caused by Entamoeba histolytica. |
| Ascariasis | Helminthic infection caused by intestinal roundworm Ascaris lumbricoides. |
| Filariasis | Disease caused by Wuchereria bancrofti; transmitted by Culex; causes elephantiasis. |
| Ringworm | Fungal disease caused by Microsporum, Trichophyton, Epidermophyton. |
| Innate immunity | Non-specific, inborn immunity with four barriers. |
| Acquired immunity | Pathogen-specific immunity with memory; involves B and T lymphocytes. |
| Antibody | Y-shaped protein (H₂L₂) produced by B-cells against antigens. |
| Antigen | Foreign substance that triggers an immune response. |
| Active immunity | Immunity produced by host’s own cells; slow but long-lasting. |
| Passive immunity | Ready-made antibodies given to host (e.g., colostrum, antitoxin). |
| Vaccine | Antigenic preparation introduced to develop immunity through memory. |
| Allergy | Exaggerated response of immune system to allergens (IgE-mediated). |
| Auto-immunity | Condition where body attacks its own cells (e.g., rheumatoid arthritis). |
| AIDS | Acquired Immuno Deficiency Syndrome — caused by HIV retrovirus. |
| ELISA | Enzyme-Linked Immunosorbent Assay — diagnostic test for HIV. |
| Cancer | Uncontrolled proliferation of cells without differentiation. |
| Carcinogen | Cancer-causing agent — physical, chemical or biological. |
| Oncogene | Activated proto-oncogene that causes cancer. |
| Metastasis | Spread of malignant tumour cells to distant body parts. |
| Biopsy | Microscopic examination of suspected tissue for cancer detection. |
| Chemotherapy | Use of drugs to kill cancerous cells. |
| Radiotherapy | Use of radiation to destroy tumour cells. |
| Immunotherapy | Use of biological response modifiers (e.g., α-interferon) against cancer. |
| Opioid | Drug like heroin (from Papaver somniferum) that depresses CNS. |
| Cannabinoid | Drug from Cannabis sativa — affects cardiovascular system. |
| Cocaine | CNS stimulant from Erythroxylum coca. |
| Addiction | Psychological attachment to drugs/alcohol. |
| Dependence | Body’s tendency to manifest withdrawal syndrome on stopping the drug. |
| Withdrawal syndrome | Set of symptoms (anxiety, nausea, sweating) when drug intake is stopped. |
| Macrophage | Phagocytic cell of cellular barrier; engulfs microbes. |
| Interferon | Protein released by virus-infected cells to protect non-infected cells. |
| NK cell | Natural Killer cell — part of cellular barrier of innate immunity. |
| Primary response | Initial low-intensity immune response on first exposure to antigen. |
| Secondary response | Heightened (anamnestic) immune response on subsequent exposure. |
| Memory cells | B/T cells that remember past antigens for future quick response. |
| Allergen | Substance like dust, pollen or mites that triggers an allergic reaction. |
| Histamine | Chemical released during allergic reactions causing inflammation. |
| Tumour | Abnormal mass of cells formed due to uncontrolled cell division. |
| Benign tumour | Non-invasive tumour confined to original location. |
| Malignant tumour | Invasive tumour that spreads to other parts (metastasis). |
| NACO | National AIDS Control Organisation — agency for AIDS awareness in India. |
| WHO | World Health Organisation — global health authority. |
| Reverse transcriptase | Enzyme of HIV that converts viral RNA into DNA inside host cell. |
| Helper T-cell (TH) | T-lymphocyte that helps B-cells; primary target of HIV. |
| Heroin | Opioid drug (smack) — chemically diacetylmorphine; depresses CNS. |
| Marijuana | Cannabinoid drug from inflorescence of Cannabis sativa. |
| Hashish/Charas/Ganja | Different forms of cannabinoids from Cannabis sativa. |
| Amphetamine | Synthetic stimulant drug used as drug of abuse. |
| Barbiturate | Sedative drug abused for tranquillising effect. |
| Nicotine | Alkaloid in tobacco that raises blood pressure and heart rate. |
| Anti-retroviral drug | Drug used in treatment of HIV/AIDS to prolong life. |
Important Diagrams to Practise
- Life cycle of Plasmodium in human and female Anopheles mosquito.
- Schematic structure of an antibody molecule (H₂L₂ — heavy and light chains, antigen-binding site, disulphide bonds).
- Replication of HIV inside helper T-lymphocyte (entry, reverse transcription, integration, release of new virions).
- Diagrammatic representation of the four barriers of innate immunity.
- Origin of cancer — proto-oncogene to oncogene activation flow chart.
Exam Tips
- Always write scientific names in italics or underlined — e.g., Salmonella typhi, Plasmodium, Anopheles.
- For long answers, use sub-headings such as Causative agent, Mode of transmission, Symptoms, Diagnosis, Treatment and Prevention.
- While writing about cancer, mention all four types (carcinoma, sarcoma, leukaemia, lymphoma) with examples.
- For drug abuse questions, include both prevention and rehabilitation measures.
- Remember that AIDS does not spread by handshaking, hugging, sharing food, mosquito bite or coughing — only by the four routes mentioned.
- Practise diagram of antibody — it is frequently asked in board exams.
Common Mistakes to Avoid
- Do not confuse Anopheles (malaria vector) with Culex (filariasis vector) or Aedes (dengue vector).
- Do not write H2L2 simply as “two chains”; specify two heavy and two light chains.
- Do not write that AIDS is caused by bacteria — it is caused by HIV (a retrovirus).
- Leukaemia is a cancer of WBCs in bone marrow, not of lymph nodes (which is lymphoma).
- Heroin is from Papaver somniferum; marijuana from Cannabis sativa; cocaine from Erythroxylum coca — do not mix these up.
End of Chapter 8 — Human Health and Disease. For more chapter-wise notes, MCQs and previous-year question answers, keep visiting HSLC Guru.