CBSE Class 12 Biology – Human Health and Disease
NCERT-aligned chapter resource | Biology Code 044
1. Health and Disease
Health involves physical, mental and social well-being. Disease can arise from infectious agents, genetic factors, lifestyle and environmental conditions.
2. Common Diseases
Pathogens such as viruses, bacteria, protozoans and helminths cause infectious diseases. Examples in the prescribed chapter include malaria, typhoid, pneumonia, common cold, amoebiasis and ascariasis.
3. Malaria
Malaria is caused by Plasmodium and transmitted through the bite of an infected female Anopheles mosquito. The parasite has stages in both human and mosquito hosts.
4. Immunity
Innate immunity provides non-specific defence. Acquired immunity is specific and involves memory. B lymphocytes produce antibodies, while T lymphocytes contribute to cell-mediated responses.
5. Vaccination
Vaccines expose the immune system to antigenic material in a controlled way so that immunological memory can develop. A later exposure can therefore produce a faster and stronger response.
6. AIDS
HIV attacks cells involved in immune defence, particularly CD4-positive T cells. Progressive loss of immune function makes the person vulnerable to opportunistic infections.
7. Cancer
Cancer involves uncontrolled cell division and can result from genetic changes affecting regulation of the cell cycle. Early detection and appropriate treatment improve outcomes.
8. Drugs and Alcohol Abuse
Substance abuse can affect the nervous system, health, behaviour and social functioning. Prevention includes awareness, support systems and professional intervention.
Chapter-Specific MCQs
- Malaria is transmitted by: (A) female Anopheles (B) housefly (C) Aedes only (D) tick. Answer: A.
- Antibodies are primarily produced by differentiated: (A) B cells (B) RBCs (C) platelets (D) neurons. Answer: A.
- HIV primarily compromises: (A) CD4+ T cells (B) RBCs (C) osteocytes (D) sperm. Answer: A.
Competency Questions
- Why can a person vaccinated against a pathogen respond faster on later exposure?
- Explain why malaria control requires interrupting the mosquito stage of transmission as well as treating infected people.
- How does loss of immune function increase susceptibility to opportunistic infections?