Extra Questions for Class 12 Biology Chapter 8 Human Health and Diseases
Q.1. Why is Gambusia introduced into drains and ponds?
Ans. To feed on mosquito larvae so as to eliminate the vectors responsible for causing malaria.
Q.2. Name any two physiological barriers that provide innate immunity?
Ans. Acid in stomach/saliva in mouth/tears in eyes. (Any two)
Q.3. Name the two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitization of its primary host.
Ans. Snail and Fish
Q.4. Name two STDs which can be transmitted through contaminated blood.
Ans. Hepatitis-B and AIDS are the two STDs which can be transmitted through contaminated blood.
Q.5. How does haemozoin affect the human body when released in blood during malarial infection?
Ans. Haemozoin is responsible for the chill and high fever recurring every three to four days during malarial infection
Q.6. Malaria, typhoid, pneumonia and amoebiasis are some of the human infectious diseases. Which ones of these are transmitted through mechanical carriers?
Ans. Malaria and amoebiasis are transmitted through mechanical carriers.
Q.7. How do interferons protect us?
Ans. Interferons protect non-infected cells from further viral infections, by creating cytokine barriers.
Q.8. State two different roles of spleen in the human body.
Ans. Spleen is the secondary lymphoid organ that stores lymphocytes, it filters microbes and acts as a reservoir to store erythrocytes (Any two).
Q.9. What is an autoimmune disease? Give an example.
Ans. It is an abnormal immune response in which the immune system of the body starts rejecting its own body cells or ‘self’ cells and molecules. For example, rheumatoid arthritis.
Q.10. How does colostrum provide initial protection against diseases to new born infants? Give one reason.
Ans. Colostrum contains several antibodies which are absolutely essential for developing resistance in the new-born babies.
Q.11. What is it that prevents a child to suffer from a disease he/she is vaccinated against? Give one reason.
Ans. The immunological memory induced by the vaccine in a child prevents the recurrence of a disease.
Q.12. What are interferons?
Ans. Virus infected cells secrete proteins called interferons which protect non-infected cells from
further viral infection.
Q.13. Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes.
Ans. Dengue/Chikungunya/yellow fever/Eastern equine encephalitis/West Nile fever/Zika virus
disease. (Any two)
Q.14. When does a human body elicit an anamnestic response?
Ans. At the time of secondary response.
Q.15. “Pranay suffered from measles at the age of 10 years. There are rare chances of his getting infected with the same disease for the rest of his life.” Give reason for the statement.
Ans. First exposure to the infection works as vaccination, the immune system of the body gets familiar with the nature of microorganisms and specific antibodies can be produced against infection.
Q.16. In what way are monocytes a cellular barrier in immunity?
Ans. Monocytes can phagocytose (by the process called phagocytosis) and thereby destroy the pathogens.
Q.17. State the functions of mast cells in allergy response.
Ans. Mast cells release chemicals like histamine and serotonin in allergic response.
Q.18. Why do pollen grains of some flowers trigger ‘sneezing’ in some people?
Ans. Pollen grains trigger sneezing by causing allergic reaction.
Q.19. High fever, loss of appetite, stomach pain and constipation are some of the symptoms seen in a patient. How would the doctor confirm that the patient is suffering from typhoid and not amoebiasis?
Ans. By performing Widal test.
Q.20. Name the category of the disease: Rheumatoid arthritis.
Ans. Auto-immune disease.
Q.21. Millions of chickens were killed in West Bengal, Orissa and Maharashtra recently. What was the reason?
Ans. Millions of chickens were killed (culled) in West Bengal, Orissa and Maharashtra because they were found to be infected with H5N1 virus, the causal organism of Bird Flu.