Important Questions Class 12 Biology Chapter 7 Human Health and Disease With Answers

Health is a state of complete physical, mental, and social well-being, not only absence of disease.
Infectious diseases, immunity, AIDS, cancer, and substance abuse directly affect human health.

Human Health and Disease connects daily life with core Biology, making it one of the most practical chapters in CBSE Class 12. Important Questions Class 12 Biology Chapter 7 help students revise disease transmission, immunity, vaccines, AIDS, cancer, and drug abuse for the 2026-27 board exam pattern. NCERT includes examples such as typhoid, pneumonia, common cold, malaria, amoebiasis, ascariasis, filariasis, ringworm, antibody structure, HIV replication, cancer detection, and adolescence-related substance abuse.

Key Takeaways

• Health: Health includes physical, mental, and social well-being, not only freedom from disease.
• Infectious Diseases: Pathogens include bacteria, viruses, fungi, protozoans, and helminths.
• Immunity: Innate immunity is present from birth, while acquired immunity is pathogen-specific and memory-based.
• AIDS and Cancer: AIDS weakens helper T-lymphocytes, while cancer involves uncontrolled cell division and metastasis.

Important Questions Class 12 Biology Chapter 7 Structure 2026-27

Important Questions Class 12 Biology Chapter 7 for CBSE 2026-27

Students searching for this chapter usually need direct board-style answers, not general health advice. CBSE 2026-27 questions can test disease examples, immune responses, AIDS transmission, cancer diagnosis, and prevention of drug abuse.

1. What is health according to Class 12 Biology?

Health is a state of complete physical, mental, and social well-being. It does not only mean absence of disease or physical fitness.

1. Good health improves work efficiency.
2. It increases productivity.
3. It increases longevity.
4. It reduces infant and maternal mortality.

Final answer:
Health means complete physical, mental, and social well-being.

2. What factors affect human health?

Human health is affected by genetic disorders, infections, and lifestyle. Food, water, rest, exercise, and habits also influence health.

1. Genetic disorders may be present from birth.
2. Infections occur due to pathogens.
3. Lifestyle includes diet, exercise, rest, and habits.
4. Mental state can influence immunity.

Final fact:
The nervous and endocrine systems influence immune function.

3. What is the difference between infectious and non-infectious diseases?

Infectious diseases spread from one person to another, while non-infectious diseases do not spread through transmission.

Final fact:
AIDS is infectious, while cancer is non-infectious.

Human Health and Disease Class 12 Biology Important Questions on Common Diseases

Disease-based questions need the pathogen, symptoms, mode of transmission, and prevention. Indian school exams often ask typhoid, pneumonia, malaria, amoebiasis, ascariasis, filariasis, and ringworm from NCERT.

4. What are pathogens?

Pathogens are disease-causing organisms that enter the body, multiply, and disturb normal body functions. They can cause tissue damage and symptoms.

Types of pathogens include:

1. Bacteria
2. Viruses
3. Fungi
4. Protozoans
5. Helminths

Final fact:
Most parasites are pathogens because they harm their host.

5. Which bacterium causes typhoid?

Salmonella typhi causes typhoid fever in humans. It enters the small intestine through contaminated food and water.

Symptoms:

1. Sustained high fever of 39°C to 40°C.
2. Weakness.
3. Stomach pain.
4. Constipation.
5. Headache.
6. Loss of appetite.

Final fact:
Severe typhoid can cause intestinal perforation and death.

6. What is Widal test Class 12 Biology?

Widal test confirms typhoid fever. It detects antibodies produced against Salmonella typhi.

1. Typhoid spreads through contaminated food and water.
2. Salmonella typhi enters the intestine.
3. The pathogen can migrate through blood.
4. Widal test helps confirm infection.

Final answer:
Widal test is used for typhoid diagnosis.

7. Who was Typhoid Mary?

Typhoid Mary was Mary Mallon, a typhoid carrier who spread typhoid through food she prepared. She worked as a cook.

1. She carried Salmonella typhi.
2. She did not stop transmitting the disease.
3. She spread typhoid for several years.

Final fact:
Typhoid Mary is a classic carrier case in medicine.

8. Which bacteria cause pneumonia?

Streptococcus pneumoniae and Haemophilus influenzae cause pneumonia in humans. They infect the alveoli of lungs.

Symptoms:

1. Fever.
2. Chills.
3. Cough.
4. Headache.
5. Difficulty in breathing.
6. Bluish lips and fingernails in severe cases.

Final fact:
Pneumonia spreads through droplets, aerosols, or shared utensils.

9. Which virus causes common cold?

Rhinoviruses cause common cold. They infect the nose and respiratory passage but not the lungs.

Symptoms:

1. Nasal congestion.
2. Nasal discharge.
3. Sore throat.
4. Hoarseness.
5. Cough.
6. Headache.
7. Tiredness.

Final fact:
Common cold usually lasts for 3-7 days.

Class 12 Biology Human Health and Disease Questions With Answers on Malaria and Parasites

Parasite-based questions usually ask the disease, causative organism, vector, symptoms, and life cycle. Malaria is the most important protozoan disease in this chapter.

10. Which organism causes malaria?

Plasmodium causes malaria. Different species cause different types of malaria.

Species include:

1. Plasmodium vivax.
2. Plasmodium malariae.
3. Plasmodium falciparum.

Final fact:
Plasmodium falciparum causes malignant malaria, which can be fatal.

11. What is the infectious stage of Plasmodium in humans?

Sporozoite is the infectious stage of Plasmodium in humans. It enters through the bite of infected female Anopheles mosquito.

1. The mosquito injects sporozoites.
2. Sporozoites first reach liver cells.
3. They later attack red blood cells.
4. RBC rupture causes fever and chills.

Final answer:
Sporozoite is the infectious stage.

12. Why does malaria cause chills and high fever?

Malaria causes chills and high fever because ruptured RBCs release haemozoin. This toxic substance triggers recurring fever.

1. Plasmodium multiplies inside RBCs.
2. Infected RBCs rupture.
3. Haemozoin is released.
4. Chills and high fever recur every three to four days.

Final fact:
Haemozoin release causes malarial fever cycles.

13. Why does Plasmodium need two hosts?

Plasmodium needs humans and female Anopheles mosquitoes to complete its life cycle. The mosquito also acts as the vector.

1. Human host supports multiplication in liver cells and RBCs.
2. Mosquito host supports further development.
3. Sporozoites are stored in mosquito salivary glands.
4. Mosquito bite transfers infection to another human.

Final fact:
Female Anopheles mosquito transmits malaria.

14. What causes amoebiasis?

Entamoeba histolytica causes amoebiasis or amoebic dysentery. It lives in the large intestine of humans.

Symptoms:

1. Constipation.
2. Abdominal pain.
3. Cramps.
4. Stools with excess mucus.
5. Stools with blood clots.

Final fact:
Houseflies act as mechanical carriers for amoebiasis.

15. What causes ascariasis?

Ascaris causes ascariasis in humans. It is a common intestinal roundworm.

Symptoms:

1. Internal bleeding.
2. Muscular pain.
3. Fever.
4. Anaemia.
5. Intestinal blockage.

Mode of infection:
Contaminated water, vegetables, fruits, and soil carry eggs of the parasite.

Final fact:
Ascaris eggs leave the body through faeces.

16. What causes elephantiasis or filariasis?

Wuchereria causes elephantiasis or filariasis. Wuchereria bancrofti and Wuchereria malayi are the main filarial worms.

1. The worms live in lymphatic vessels.
2. They cause chronic inflammation.
3. Lower limbs often swell and deform.
4. Genital organs may also be affected.

Final fact:
Female mosquito vectors transmit filariasis.

17. Which fungi cause ringworm?

Microsporum, Trichophyton, and Epidermophyton cause ringworm. Ringworm affects skin, nails, and scalp.

Symptoms:

1. Dry scaly lesions.
2. Intense itching.
3. Infection in skin folds.
4. Infection between toes or groin area.

Final fact:
Heat and moisture help ringworm fungi grow.

Class 12 Biology Human Health and Disease NCERT Questions on Prevention

Prevention questions need personal hygiene, public hygiene, vaccination, vector control, and safe water measures. CBSE 2026-27 can frame these as case-based public health questions.

18. What public health measures prevent infectious diseases?

Public health measures include waste disposal, clean drinking water, vector control, vaccination, and hygiene in food and water resources.

Measures:

1. Proper disposal of waste and excreta.
2. Cleaning and disinfection of water reservoirs.
3. Hygienic practices in public catering.
4. Control of insect vectors.
5. Vaccination against infectious diseases.

Final fact:
Public hygiene prevents food-borne, water-borne, and vector-borne diseases.

19. How can malaria and filariasis be prevented?

Malaria and filariasis can be prevented by controlling mosquito vectors and their breeding places.

Measures:

1. Avoid water stagnation.
2. Clean household coolers regularly.
3. Use mosquito nets.
4. Introduce Gambusia fish in ponds.
5. Spray insecticides in ditches and swamps.
6. Use wire mesh on doors and windows.

Final fact:
Vector control is essential for mosquito-borne diseases.

20. How can water-borne diseases be prevented?

Water-borne diseases can be prevented through clean water, sanitation, and safe food practices.

Measures:

1. Drink clean water.
2. Wash fruits and vegetables.
3. Avoid food contaminated with faecal matter.
4. Dispose excreta properly.
5. Disinfect water reservoirs.

Final answer:
Safe water and sanitation prevent typhoid, amoebiasis, and ascariasis.

Immunity Class 12 Biology Questions for CBSE 2026-27

Immunity questions appear often because they connect barriers, antibodies, vaccination, lymphoid organs, allergy, and autoimmunity. The most searched queries include innate immunity, acquired immunity, active immunity, passive immunity, and antibody structure.

21. What is immunity?

Immunity is the ability of the host to fight disease-causing organisms. The immune system provides this protection.

1. The body faces many infectious agents daily.
2. Only some exposures cause disease.
3. The immune system defends against most pathogens.

Final answer:
Immunity is the body’s defence ability against pathogens.

22. What are the two types of immunity?

The two types of immunity are innate immunity and acquired immunity.

1. Innate immunity is present from birth.
2. It is non-specific.
3. Acquired immunity develops after exposure.
4. It is pathogen-specific and memory-based.

Final fact:
Acquired immunity gives stronger secondary response.

23. What is innate immunity Class 12 Biology?

Innate immunity is a non-specific defence present at birth. It blocks entry or growth of foreign agents.

Barriers include:

1. Physical barriers.
2. Physiological barriers.
3. Cellular barriers.
4. Cytokine barriers.

Final answer:
Innate immunity gives immediate general protection.

24. Name the four barriers of innate immunity.

The four barriers of innate immunity are physical, physiological, cellular, and cytokine barriers.

1. Physical barriers: skin and mucus.
2. Physiological barriers: stomach acid, saliva, tears.
3. Cellular barriers: neutrophils, monocytes, macrophages, natural killer cells.
4. Cytokine barriers: interferons from virus-infected cells.

Final fact:
Interferons protect non-infected cells from viral infection.

25. What is acquired immunity Class 12 Biology?

Acquired immunity is pathogen-specific immunity with memory. It produces a stronger response on second exposure.

1. First exposure gives primary response.
2. Primary response has low intensity.
3. Second exposure gives secondary response.
4. Secondary response is highly intensified.

Final fact:
Secondary response is also called anamnestic response.

26. What is the difference between humoral immunity and cell-mediated immunity?

Humoral immunity uses antibodies, while cell-mediated immunity uses T-lymphocytes.

Final fact:
CMI is responsible for graft rejection.

27. What is antibody structure Class 12 Biology?

An antibody has four peptide chains: two heavy chains and two light chains. It is represented as H2L2.

Structure:

1. Two heavy chains.
2. Two light chains.
3. Chain arrangement gives antigen-binding ability.

Examples of antibodies:
IgA, IgM, IgE, IgG

Final answer:
Antibody molecule is represented as H2L2.

28. What is the difference between active and passive immunity?

Active immunity forms antibodies inside the host, while passive immunity gives ready-made antibodies directly.

Final fact:
Colostrum contains IgA antibodies.

29. Why is colostrum important for a newborn baby?

Colostrum is important because it contains abundant IgA antibodies. These antibodies protect the newborn infant.

1. Colostrum is yellowish fluid.
2. It is secreted in early lactation.
3. It provides passive immunity.

Final fact:
The foetus also receives antibodies through the placenta.

30. What is vaccination Class 12 Biology?

Vaccination introduces antigenic proteins or weakened pathogens into the body to generate immune memory. It protects against future infection.

1. Vaccine triggers antibody production.
2. Memory B-cells and T-cells form.
3. Later exposure gives faster response.
4. The pathogen gets neutralised quickly.

Final fact:
Hepatitis B vaccine is produced from yeast using recombinant DNA technology.

31. What is allergy Class 12 Biology?

Allergy is an exaggerated immune response to certain environmental antigens called allergens. IgE antibodies mediate allergic responses.

Common allergens:

1. Dust mites.
2. Pollens.
3. Animal dander.

Symptoms:
Sneezing, watery eyes, running nose, and breathing difficulty.

Final fact:
Histamine and serotonin released from mast cells cause allergy symptoms.

32. What is autoimmunity?

Autoimmunity occurs when the body attacks its own cells due to genetic or unknown reasons. It causes autoimmune disease.

1. The immune system normally recognises self and non-self.
2. Failure of self-recognition damages body cells.
3. Rheumatoid arthritis is an autoimmune disease.

Final answer:
Autoimmunity means immune attack against self-cells.

33. Name the primary and secondary lymphoid organs.

Primary lymphoid organs are bone marrow and thymus, while secondary lymphoid organs include spleen, lymph nodes, tonsils, Peyer’s patches, and appendix.

Primary lymphoid organs:

1. Bone marrow.
2. Thymus.

Secondary lymphoid organs:

1. Spleen.
2. Lymph nodes.
3. Tonsils.
4. Peyer’s patches.
5. Appendix.

Final fact:
MALT forms about 50 percent of lymphoid tissue in the human body.

AIDS Class 12 Biology Questions With Answers

AIDS questions need exact routes of HIV transmission, HIV replication, helper T-lymphocyte destruction, ELISA, and prevention. This is a high-intent topic in Class 12 Biology searches.

34. What is AIDS?

AIDS stands for Acquired Immuno Deficiency Syndrome. It is caused by Human Immunodeficiency Virus.

1. Acquired means gained during life.
2. Immunodeficiency means weakened immune system.
3. Syndrome means a group of symptoms.

Final fact:
AIDS was first reported in 1981.

35. What type of virus is HIV?

HIV is a retrovirus with an RNA genome enclosed inside an envelope. It uses reverse transcriptase during replication.

1. HIV contains RNA.
2. Reverse transcriptase makes viral DNA.
3. Viral DNA enters host DNA.
4. Infected cells produce virus particles.

Final answer:
HIV is an RNA retrovirus.

36. How is HIV transmitted?

HIV spreads through body fluids, not by touch or casual contact.

Routes of transmission:

1. Sexual contact with an infected person.
2. Transfusion of contaminated blood.
3. Sharing infected needles.
4. Infected mother to child through placenta.

Final fact:
HIV does not spread by mere physical contact.

37. How does HIV cause immunodeficiency?

HIV causes immunodeficiency by reducing helper T-lymphocytes in the body. This weakens immune defence.

Steps:

1. HIV enters macrophages.
2. Viral RNA forms viral DNA by reverse transcriptase.
3. Viral DNA enters host DNA.
4. Macrophages produce virus particles.
5. HIV enters helper T-lymphocytes.
6. Helper T-cells decrease gradually.

Final fact:
Low helper T-cell count makes patients vulnerable to infections.

38. Which test is used for AIDS diagnosis?

ELISA is widely used for AIDS diagnosis. ELISA stands for enzyme-linked immunosorbent assay.

1. HIV infection weakens immunity.
2. ELISA detects infection markers.
3. Early testing helps control spread.

Final answer:
ELISA is used for AIDS diagnosis.

39. How can AIDS be prevented?

AIDS can be prevented through safe sex, screened blood, disposable needles, and public awareness.

Measures:

1. Use safe blood from blood banks.
2. Use disposable needles and syringes.
3. Avoid sharing injection needles.
4. Practise safe sex.
5. Promote regular HIV testing in high-risk groups.

Final fact:
NACO and NGOs educate people about AIDS in India.

Cancer Class 12 Biology Questions With Answers

Cancer-related searches usually focus on normal cells versus cancer cells, benign and malignant tumours, metastasis, carcinogens, diagnosis, and treatment.

40. What is cancer?

Cancer is a disease in which cells lose normal growth control and divide continuously. These cells form masses called tumours.

1. Normal cells show contact inhibition.
2. Cancer cells lose contact inhibition.
3. They keep dividing.
4. Tumours form from uncontrolled cell growth.

Final fact:
Cancer is a major cause of death worldwide.

41. How are cancer cells different from normal cells?

Cancer cells lose contact inhibition, while normal cells stop uncontrolled growth after contact with other cells.

Final fact:
Loss of contact inhibition causes tumour formation.

42. What is the difference between benign and malignant tumours?

Benign tumours remain confined, while malignant tumours invade surrounding tissues and spread.

Final fact:
Malignant tumours are more dangerous.

43. What is metastasis Class 12 Biology?

Metastasis is the spread of cancer cells from one body site to distant sites through blood. It is the most feared property of malignant tumours.

1. Cells break away from the tumour.
2. They enter blood circulation.
3. They lodge in distant tissues.
4. They start new tumours.

Final answer:
Metastasis means formation of secondary tumours.

44. What are carcinogens?

Carcinogens are physical, chemical, or biological agents that induce cancer. They transform normal cells into cancerous cells.

Types:

1. Physical carcinogens: X-rays, gamma rays, UV rays.
2. Chemical carcinogens: tobacco smoke chemicals.
3. Biological carcinogens: oncogenic viruses.

Final fact:
Tobacco smoke is a major cause of lung cancer.

45. How is cancer detected?

Cancer is detected through biopsy, histopathology, blood tests, bone marrow tests, radiography, CT, MRI, antibodies, and molecular biology techniques.

1. Biopsy examines suspected tissue.
2. Histopathology studies stained tissue sections.
3. CT gives three-dimensional internal images.
4. MRI detects pathological and physiological changes.
5. Molecular techniques detect inherited susceptibility genes.

Final fact:
Early detection improves treatment success.

46. How is cancer treated?

Cancer is treated through surgery, radiotherapy, chemotherapy, and immunotherapy. Many cancers use combined treatment.

1. Surgery removes tumour mass.
2. Radiotherapy kills tumour cells using radiation.
3. Chemotherapy uses anticancer drugs.
4. Immunotherapy uses biological response modifiers.

Example:
Alpha-interferon activates immune response against tumours.

Final fact:
Cancer treatment depends on type and stage.

Drug and Alcohol Abuse Class 12 Biology Questions for Indian Students

Drug abuse questions connect Biology with adolescent health, peer pressure, addiction, dependence, and prevention. CBSE 2026-27 may ask these as value-based or case-based questions.

47. What is drug abuse?

Drug abuse means using drugs for non-medicinal purposes or in harmful amounts or frequency. It impairs physical, physiological, or psychological functions.

1. Some medicines are useful when prescribed.
2. Misuse can damage health.
3. Repeated use can lead to addiction.

Final fact:
Drug abuse is common among vulnerable adolescents.

48. What are opioids?

Opioids are drugs that bind to opioid receptors in the central nervous system and gastrointestinal tract. Heroin is an opioid.

1. Heroin is chemically diacetylmorphine.
2. It comes from morphine.
3. Morphine comes from Papaver somniferum latex.
4. Heroin acts as a depressant.

Final fact:
Heroin is commonly called smack.

49. What are cannabinoids?

Cannabinoids are chemicals that interact with cannabinoid receptors mainly in the brain. They come from Cannabis sativa.

Products include:

1. Marijuana.
2. Hashish.
3. Charas.
4. Ganja.

Final fact:
Cannabinoids affect the cardiovascular system.

50. What is cocaine?

Cocaine is a coca alkaloid obtained from Erythroxylum coca. It stimulates the central nervous system.

1. Cocaine is also called coke or crack.
2. It interferes with dopamine transport.
3. It produces euphoria and increased energy.
4. Excess dose causes hallucinations.

Final fact:
Cocaine is usually snorted.

51. Why is tobacco harmful?

Tobacco is harmful because it contains nicotine and many cancer-linked chemicals. Nicotine raises blood pressure and heart rate.

Effects:

1. Lung cancer.
2. Urinary bladder cancer.
3. Throat cancer.
4. Bronchitis.
5. Emphysema.
6. Coronary heart disease.
7. Gastric ulcer.

Final fact:
Smoking increases carbon monoxide in blood and reduces oxygen transport.

52. Why are adolescents vulnerable to drug and alcohol abuse?

Adolescents are vulnerable because this phase includes biological, behavioural, mental, and psychological changes.

Common causes:

1. Curiosity.
2. Peer pressure.
3. Stress from academics.
4. Need for adventure.
5. Misleading media influence.
6. Unsupportive family environment.

Final fact:
Adolescence usually covers 12-18 years of age.

53. What is addiction?

Addiction is a psychological attachment to effects such as euphoria and temporary well-being. It drives repeated drug or alcohol use.

1. Repeated use increases tolerance.
2. Receptors respond only to higher doses.
3. Higher intake increases addiction risk.
4. Even one use can become a fore-runner to addiction.

Final fact:
Addiction can become self-destructive.

54. What is dependence?

Dependence is the body’s tendency to show withdrawal symptoms when drug or alcohol use stops suddenly.

Withdrawal symptoms include:

1. Anxiety.
2. Shakiness.
3. Nausea.
4. Sweating.

Final fact:
Severe withdrawal may need medical supervision.

55. What are the harmful effects of drug and alcohol abuse?

Drug and alcohol abuse can cause reckless behaviour, violence, coma, death, infections, and long-term organ damage.

Effects include:

1. Respiratory failure.
2. Heart failure.
3. Cerebral haemorrhage.
4. AIDS and Hepatitis B through infected needles.
5. Liver cirrhosis.
6. Nervous system damage.

Final fact:
Drug or alcohol use during pregnancy can harm the foetus.

56. How can drug and alcohol abuse be prevented?

Drug and alcohol abuse can be prevented through education, counselling, family support, peer support, and medical help.

Measures:

1. Avoid undue peer pressure.
2. Accept disappointments and failures.
3. Seek help from parents and trusted friends.
4. Watch for danger signs.
5. Consult psychologists, psychiatrists, or rehabilitation centres.

Final fact:
Early intervention reduces long-term harm.

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