CBSE Class 12 Biology Short Answer Questions (NCERT): Human Health and Disease

Course & Examination Details

• Course: CBSE Class 12 Biology
• Unit: Unit III – Biology and Human Welfare
• Chapter: Chapter 8 – Human Health and Disease
• Prescribed Textbook: NCERT Biology Class XII
• Examination: CBSE Class 12 Board Examination
• Question Type: Short Answer Type
• Answer Length: 60–80 words each

Section A: Health and Its Significance

Q1. Define health and explain why it is not merely the absence of disease.

Answer:
Health is a state of complete physical, mental, and social well-being. It is not merely the absence of disease because a person may be disease-free but still suffer from stress, malnutrition, or social problems that affect overall well-being.

Q2. Explain the factors that influence human health.

Answer:
Human health is influenced by genetic makeup, environmental conditions, lifestyle habits, nutrition, sanitation, and socio-economic factors. Balanced diet, personal hygiene, clean surroundings, and stress-free life contribute to good health.

Q3. Differentiate between congenital and acquired diseases.

Answer:
Congenital diseases are present at birth and usually result from genetic defects, whereas acquired diseases develop after birth due to infections, lifestyle factors, or environmental influences.

Q4. Why is health considered a social responsibility?

Answer:
Health depends on sanitation, safe drinking water, nutrition, education, and healthcare facilities, which are influenced by social and governmental efforts, making health a social responsibility.

Q5. Explain the relationship between health and economic development.

Answer:
Healthy individuals are more productive and contribute to economic growth. Poor health increases medical expenses and reduces efficiency, affecting national development.

Section B: Common Human Diseases

Q6. Describe typhoid with respect to causative agent and symptoms.

Answer:
Typhoid is caused by Salmonella typhi and spreads through contaminated food and water. Symptoms include sustained fever, weakness, abdominal pain, constipation, and loss of appetite.

Q7. Explain pneumonia and its mode of transmission.

Answer:
Pneumonia is caused by bacteria such as Streptococcus pneumoniae. It spreads through inhalation of droplets released during coughing or sneezing, causing fever, cough, and breathing difficulty.

Q8. Describe malaria and its causative organism.

Answer:
Malaria is caused by the protozoan Plasmodium and transmitted by female Anopheles mosquitoes. It causes recurrent fever, chills, and sweating.

Q9. What is amoebiasis? Mention its symptoms.

Answer:
Amoebiasis is caused by Entamoeba histolytica and spreads through contaminated food and water. Symptoms include diarrhoea, abdominal pain, and dysentery.

Q10. Distinguish between infectious and non-infectious diseases.

Answer:
Infectious diseases are caused by pathogens and spread from person to person, while non-infectious diseases do not spread and include disorders like diabetes and cancer.

Section C: Pathogens and Parasites

Q11. What are pathogens? Name their major types.

Answer:
Pathogens are disease-causing organisms. Major types include bacteria, viruses, protozoa, fungi, and helminths.

Q12. Explain the role of parasites in causing diseases.

Answer:
Parasites live in or on the host and derive nutrition, harming the host’s body and causing diseases such as malaria and ascariasis.

Q13. Differentiate between ectoparasites and endoparasites.

Answer:
Ectoparasites live on the body surface, like lice, while endoparasites live inside the body, such as tapeworms and Plasmodium.

Q14. How does poor sanitation promote infectious diseases?

Answer:
Poor sanitation contaminates food and water, facilitating the spread of pathogens and increasing incidence of waterborne diseases.

Q15. Explain how vectors help in disease transmission.

Answer:
Vectors like mosquitoes transmit pathogens from infected to healthy individuals, playing a key role in spreading diseases such as malaria.

Section D: Immunity

Q16. Define immunity and explain its importance.

Answer:
Immunity is the ability of the body to resist infections. It protects against pathogens and helps maintain health.

Q17. Describe innate immunity.

Answer:
Innate immunity is non-specific defence present from birth. It includes physical, physiological, cellular, and cytokine barriers that provide immediate protection.

Q18. Explain acquired immunity.

Answer:
Acquired immunity is pathogen-specific and develops after exposure. It involves B and T lymphocytes and shows immunological memory.

Q19. Differentiate between innate and acquired immunity.

Answer:
Innate immunity is non-specific and lacks memory, while acquired immunity is specific and has memory, providing long-term protection.

Q20. What role do lymphocytes play in immunity?

Answer:
B-lymphocytes produce antibodies, while T-lymphocytes help in cell-mediated immunity, together forming acquired immunity.

Section E: Vaccination and Immunisation

Q21. Explain the principle of vaccination.

Answer:
Vaccination introduces antigens to stimulate antibody production and memory cell formation, providing protection without causing disease.

Q22. Differentiate between active and passive immunity.

Answer:
Active immunity involves antibody production by the body and is long-lasting, while passive immunity involves transfer of antibodies and is short-lived.

Q23. What are recombinant vaccines? Give an example.

Answer:
Recombinant vaccines are produced using genetic engineering. Hepatitis B vaccine is an example.

Q24. Explain herd immunity.

Answer:
Herd immunity occurs when a large proportion of a population becomes immune, reducing disease spread and protecting unvaccinated individuals.

Q25. Why is vaccination considered a preventive measure?

Answer:
Vaccination prevents diseases before infection occurs, reducing mortality and disease burden.

Section F: Allergies

Q26. What is an allergy?

Answer:
An allergy is an exaggerated immune response to harmless substances known as allergens.

Q27. Explain the mechanism of allergic reactions.

Answer:
Allergic reactions involve IgE antibodies and release of histamine from mast cells, causing inflammation and symptoms.

Q28. Name common allergens and symptoms.

Answer:
Common allergens include pollen and dust mites. Symptoms include sneezing, watery eyes, and skin rashes.

Q29. How are allergies treated?

Answer:
Allergies are treated using antihistamines, steroids, and by avoiding allergens.

Q30. Why do allergies vary among individuals?

Answer:
Genetic factors and immune sensitivity differ among individuals, causing variation in allergic responses.

Section G: Autoimmune Diseases

Q31. What are autoimmune diseases?

Answer:
Autoimmune diseases occur when the immune system attacks the body’s own tissues.

Q32. Explain rheumatoid arthritis as an autoimmune disorder.

Answer:
In rheumatoid arthritis, immune cells attack joint tissues, causing inflammation, pain, and joint damage.

Q33. What causes autoimmune diseases?

Answer:
They are caused by genetic predisposition and environmental triggers leading to loss of self-tolerance.

Q34. How is Type 1 diabetes an autoimmune disease?

Answer:
In Type 1 diabetes, immune cells destroy insulin-producing pancreatic cells.

Q35. Why are autoimmune diseases difficult to cure?

Answer:
They involve self-antigens, making suppression of immunity risky and complex.

Section H: Drugs and Alcohol Abuse

Q36. What is drug abuse?

Answer:
Drug abuse is excessive or improper use of drugs affecting physical and mental health.

Q37. Explain the effects of alcohol on the human body.

Answer:
Alcohol depresses the nervous system, damages the liver, affects judgment, and can lead to addiction.

Q38. What are the reasons for drug abuse among adolescents?

Answer:
Peer pressure, curiosity, stress, lack of awareness, and family problems contribute to drug abuse.

Q39. Explain the harmful effects of drug addiction.

Answer:
Drug addiction causes physical dependence, mental disorders, social problems, and risk of infections like HIV.

Q40. How does drug abuse lead to social problems?

Answer:
Drug abuse affects family relationships, academic performance, and can lead to crime and unemployment.

Section I: Prevention and Control

Q41. Suggest measures to prevent drug abuse.

Answer:
Education, counselling, family support, awareness programmes, and rehabilitation help prevent drug abuse.

Q42. Why is counselling important in drug abuse prevention?

Answer:
Counselling helps individuals cope with stress, build confidence, and avoid harmful habits.

Q43. Explain the role of family in maintaining health.

Answer:
Family provides emotional support, guidance, and promotes healthy habits essential for well-being.

Q44. How does personal hygiene prevent diseases?

Answer:
Personal hygiene reduces exposure to pathogens, preventing infectious diseases.

Q45. Why is immunisation important in public health?

Answer:
Immunisation prevents disease outbreaks and protects vulnerable populations.

Section J: Integrated Concepts

Q46. How are immunity and vaccination related?

Answer:
Vaccination induces acquired immunity by stimulating antibody production and memory cells.

Q47. Why is awareness important in disease prevention?

Answer:
Awareness promotes healthy practices, early detection, and timely treatment.

Q48. Explain the significance of balanced diet in health.

Answer:
Balanced diet provides essential nutrients, boosts immunity, and prevents deficiency diseases.

Q49. How does stress affect human health?

Answer:
Stress weakens immunity, affects mental health, and increases disease susceptibility.

Q50. Why is Human Health and Disease an important chapter?

Answer:
It connects biology with real life, promoting disease prevention and healthy lifestyle choices.

✔ Strictly NCERT-Based | ✔ CBSE Board Aligned | ✔ Ideal for 3–4 Mark Answers