Chapter 8: Human Health and Disease – Long Answer Type Questions

CBSE Class 12 Biology Long 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: Long Answer Type
Answer Length: 120–150 words each
Syllabus Alignment: Strictly NCERT-based

Section A: Health and Its Significance

Q1. Define health and explain the factors affecting human health.

Answer:
Health is a state of complete physical, mental, and social well-being and not merely the absence of disease. Human health is influenced by several interrelated factors. Genetic makeup plays a key role in determining susceptibility to diseases. Environmental factors such as clean water, sanitation, and pollution levels significantly affect health. Lifestyle choices including diet, exercise, sleep, and stress management are crucial determinants. Socio-economic conditions like income, education, and access to healthcare also impact overall health. A balanced interaction among these factors ensures healthy living and disease resistance.

Q2. Why is health considered a social and national concern?

Answer:
Health is considered a social and national concern because it directly affects productivity, economic growth, and quality of life. Poor health reduces work efficiency and increases healthcare expenditure, burdening families and governments. Social factors like sanitation, clean drinking water, education, and public health awareness significantly influence community health. National immunisation programmes and disease-control measures highlight the collective responsibility toward health. Thus, maintaining public health is essential for sustainable national development.

Section B: Common Human Diseases

Q3. Describe typhoid with respect to causative agent, transmission, and symptoms.

Answer:
Typhoid is a bacterial disease caused by Salmonella typhi. It spreads through consumption of contaminated food and water. The bacteria enter the intestinal tract and multiply, leading to systemic infection. Symptoms include prolonged high fever, weakness, abdominal pain, constipation or diarrhoea, and loss of appetite. Severe cases may cause intestinal perforation. Prevention involves maintaining hygiene, safe drinking water, and vaccination.

Q4. Explain pneumonia and its effects on the respiratory system.

Answer:
Pneumonia is a respiratory disease caused by bacteria such as Streptococcus pneumoniae. It spreads via inhalation of droplets from infected individuals. The pathogen infects alveoli, causing them to fill with fluid and pus. This reduces oxygen exchange, leading to breathing difficulty, chest pain, cough, and fever. In severe cases, it may cause hypoxia. Vaccination and early treatment are effective preventive measures.

Q5. Describe malaria and its life cycle in humans.

Answer:
Malaria is caused by the protozoan Plasmodium and transmitted by the female Anopheles mosquito. In humans, sporozoites enter the bloodstream and infect liver cells, multiplying asexually. Merozoites released from liver cells invade red blood cells, causing their rupture and releasing toxins. This leads to periodic fever, chills, and sweating. Prevention includes mosquito control and antimalarial drugs.

Section C: Pathogens and Parasites

Q6. What are pathogens? Explain different types with examples.

Answer:
Pathogens are disease-causing organisms that invade the host body. Major types include viruses (HIV, influenza virus), bacteria (Salmonella, Mycobacterium), protozoa (Plasmodium, Entamoeba), fungi (ringworm), and helminths (Ascaris). Each pathogen has specific modes of transmission and disease mechanisms. Understanding pathogens helps in effective prevention and treatment.

Q7. Explain the role of vectors in disease transmission.

Answer:
Vectors are organisms that transmit pathogens from one host to another. Mosquitoes, flies, and ticks act as vectors. For example, female Anopheles mosquito transmits malaria, while Aedes mosquito spreads dengue. Vectors facilitate disease spread without being affected themselves. Vector control is essential for disease prevention.

Section D: Immunity

Q8. Define immunity and explain innate immunity.

Answer:
Immunity is the ability of the body to resist and fight infections. Innate immunity is the first line of defence present from birth and is non-specific. It includes physical barriers (skin), physiological barriers (acidic stomach secretions), cellular barriers (phagocytes), and cytokine barriers (interferons). It provides immediate protection but does not have memory.

Q9. Describe acquired immunity and its characteristics.

Answer:
Acquired immunity is pathogen-specific immunity developed after exposure to antigens. It involves B-lymphocytes and T-lymphocytes. Key features include specificity, memory, and diversity. Once exposed, the immune system responds faster and stronger upon re-exposure, providing long-term protection.

Q10. Differentiate between active and passive immunity.

Answer:
Active immunity results from the body’s own immune response after infection or vaccination and is long-lasting due to memory cells. Passive immunity involves transfer of ready-made antibodies and provides immediate but short-term protection, such as maternal antibodies.

Section E: Vaccination

Q11. Explain the principle and importance of vaccination.

Answer:
Vaccination introduces weakened or killed antigens to stimulate antibody production without causing disease. It induces immunological memory, providing long-term protection. Vaccination prevents epidemics, reduces mortality, and promotes herd immunity. It is a cost-effective preventive healthcare measure.

Q12. Describe different types of vaccines with examples.

Answer:
Vaccines include live attenuated vaccines (BCG), killed vaccines (typhoid), subunit vaccines, and recombinant vaccines (Hepatitis B). Each type stimulates immune response safely and effectively.

Section F: Allergies

Q13. Explain allergies and their mechanism.

Answer:
Allergies are exaggerated immune responses to harmless substances called allergens. Exposure triggers IgE antibodies, leading to histamine release from mast cells. Symptoms include sneezing, rashes, and asthma. Antihistamines help manage symptoms.

Q14. Why do allergic responses differ among individuals?

Answer:
Genetic differences and immune sensitivity cause variation in allergic responses. Environmental exposure also influences severity.

Section G: Autoimmune Diseases

Q15. What are autoimmune diseases? Explain with an example.

Answer:
Autoimmune diseases occur when the immune system attacks self-antigens. In rheumatoid arthritis, immune cells damage joint tissues, causing inflammation and pain. Genetic and environmental factors contribute to these disorders.

Q16. Why are autoimmune diseases difficult to treat?

Answer:
They involve self-tissues, making immune suppression risky. Long-term management is required.

Section H: Drugs and Alcohol Abuse

Q17. Explain drug abuse and its effects on health.

Answer:
Drug abuse is excessive use of psychoactive substances affecting brain and behaviour. It causes addiction, mental disorders, organ damage, and social problems. Prevention requires awareness and counselling.

Q18. Describe the harmful effects of alcohol abuse.

Answer:
Alcohol abuse damages liver, impairs judgment, causes addiction, and leads to social and health problems like cirrhosis.

Q19. Explain reasons for drug abuse among adolescents.

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

Q20. Suggest preventive measures against drug and alcohol abuse.

Answer:
Education, counselling, family support, awareness programmes, and rehabilitation are key preventive strategies.

Section I: Prevention and Control

Q21. How does personal hygiene help prevent diseases?

Answer:
Personal hygiene reduces pathogen exposure, preventing infections like diarrhoea and respiratory diseases.

Q22. Explain the role of immunisation in public health.

Answer:
Immunisation prevents outbreaks, reduces disease burden, and protects vulnerable populations.

Q23. Why is awareness important in maintaining health?

Answer:
Awareness promotes healthy habits, early diagnosis, and disease prevention.

Q24. Explain the significance of balanced diet in immunity.

Answer:
Balanced diet supplies nutrients essential for immune cell function and disease resistance.

Q25. Why is Human Health and Disease an important chapter in biology?

Answer:
It links biology to real life, promoting disease prevention, health awareness, and responsible lifestyle choices essential for societal well-being.