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Human Health and Diseases

Q1. What is an allergy? Mention their symptoms.

Ans: The exaggerated response of the immune system to certain antigens present in the environment is called allergy.

Symptoms of allergic reactions include sneezing, watery eyes, running nose and difficulty in breathing.

Q2. List any three characteristics of cancerous cell.


  • The cells divide repeatedly with uncontrolled cell division.

  • The cancer cells do not require extracellular growth factors.

  • Cancer cells have lost the property of contact inhibition.

  • Due to repeated division, cells form a large mass of tissue called tumour.

  • The cells pass out from the tumour to new sites for forming secondary tumours.

Q3. What is innate immunity? Mention four different types of barriers of innate immunity by giving an example for each.

Ans: Innate immunity is non-specific type of defence, that is present at the time of birth. It consists of four types of barriers. They are,

  1. Physical barriers: Skin on our body, mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts.

  2. Physiological barriers: Acid in the stomach, saliva in the mouth, tears from eyes.

  3. Cellular barriers: Leukocytes like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes.

  4. Cytokine barriers: Interferons.

Q4. Name the diseases caused by the following organisms;
  1. Rhino virus

  2. Epidermophyton

  3. Salmonella typhi

  4. Wuchereria malayi

  5. Plasmodium vivax


  1. Rhino virus - Common cold

  2. Epidermophyton - Ringworms

  3. Salmonella typhi - Typhoid

  4. Wuchereria malayi - Filariasis / Elephantiasis

  5. Plasmodium vivax - Malaria

Q5. What are carcinogens? List any two types of carcinogens.

Ans: The cancer-causing agents are called carcinogens.

Carcinogens are of following types:

  1. Chemical agents: Aniline dyes, N-nitrosodimethylamine, benzopyrene, chemicals in cigarette smoke.

  2. Physical agents: Ionising radiations like X-rays and gamma-rays, non-ionising radiations like UV-rays.

  3. Biological agents: Oncogenic viruses, some parasites.

Q6. Define immunity and name two different types of immunity.

Ans: The overall ability of the host to fight the disease-causing organisms is called immunity.

Immunity is of two types:

  1. Innate immunity

  2. Acquired immunity