Exercises

1. What are the various public health measures, which you would suggest as safeguard against infectious diseases?

• Maintenance of personal and public hygiene (clean water, food, and air).
• Proper disposal of waste and excreta.
• Periodic cleaning and disinfection of water reservoirs and tanks.
• Control and elimination of vectors (e.g., mosquito control).
• Immunisation/vaccination programmes for common infectious diseases.

2. In which way has the study of biology helped us to control infectious diseases?

• Identification of pathogens and understanding their life cycles.
• Development of vaccines and immunisation protocols (e.g., smallpox eradication).
• Discovery of antibiotics (e.g., Penicillin) and other life-saving drugs.
• Use of biotechnology to produce safer vaccines (e.g., Hepatitis B).
• Advancements in diagnostic techniques like ELISA and PCR.

3. How does the transmission of each of the following diseases take place?

• (a) Amoebiasis: Through contaminated food and water (Houseflies act as mechanical carriers).
• (b) Malaria: Through the bite of an infected female Anopheles mosquito (vector).
• (c) Ascariasis: Through contaminated soil, water, or vegetables containing eggs of the parasite.
• (d) Pneumonia: By inhaling droplets/aerosols released by an infected person or sharing utensils.

4. What measure would you take to prevent water-borne diseases?

• Consumption of clean and boiled drinking water.
• Proper treatment and filtration of water in reservoirs.
• Ensuring that sewage does not contaminate water bodies.
• Maintaining strict hygiene in public catering and kitchens.

5. Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.

• A 'suitable gene' refers to a specific DNA sequence that codes for an antigenic protein of a pathogen. When this gene is introduced into the body (via a DNA vaccine), the host cells express the protein, triggering a targeted immune response and generating memory without causing the disease.

6. Name the primary and secondary lymphoid organs.

• Primary: Bone marrow and Thymus.
• Secondary: Spleen, Lymph nodes, Tonsils, Peyer’s patches (small intestine), and Appendix.

7. Expand the following abbreviations:

• (a) MALT: Mucosa-Associated Lymphoid Tissue
• (b) CMI: Cell-Mediated Immunity
• (c) AIDS: Acquired Immuno Deficiency Syndrome
• (d) NACO: National AIDS Control Organisation
• (e) HIV: Human Immuno-deficiency Virus

8. Differentiate the following:

• (a) Innate and Acquired Immunity: Innate is non-specific and present at birth; Acquired is pathogen-specific and develops after exposure, showing 'memory'.
• (b) Active and Passive Immunity: Active is when the body produces its own antibodies (slow but long-lasting); Passive is when preformed antibodies are introduced (fast but temporary).

9. Draw a well-labelled diagram of an antibody molecule. (Answer based on Fig 7.4: H2L2 structure with Antigen-binding sites)

10. What are the various routes by which transmission of human immuno-deficiency virus takes place?

• Sexual contact with an infected person.
• Transfusion of contaminated blood and blood products.
• Sharing infected needles (especially among IV drug abusers).
• From an infected mother to her child through the placenta.

11. What is the mechanism by which the AIDS virus causes deficiency of immune system?

• HIV enters Helper T-lymphocytes (TH).
• It replicates and produces progeny viruses, which attack other helper T-cells.
• This leads to a progressive decrease in the number of TH cells, severely weakening the cell-mediated immune response.
• The patient becomes susceptible to various opportunistic infections (e.g., Mycobacterium, Toxoplasma).

12. How is a cancerous cell different from a normal cell?

• Normal cells show contact inhibition, which stops their growth when they touch other cells. Cancerous cells lose this property and divide uncontrollably.
• Cancerous cells are poorly differentiated and compete with normal cells for nutrients, often starving them.
• Cancerous cells (malignant) can spread to other parts of the body (metastasis).

13. Explain what is meant by metastasis.

• Metastasis is the process where cells sloughed from a malignant tumor reach distant sites via the bloodstream and start new tumors wherever they get lodged. It is the most dangerous property of cancer.

14. List the harmful effects caused by alcohol/drug abuse.

• Reckless behaviour, vandalism, and violence.
• Damage to the nervous system and liver (Cirrhosis).
• Risk of infections like AIDS and Hepatitis B (via shared needles).
• Mental and financial distress to family and friends.
• Adverse effects on the foetus during pregnancy.

15. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

• Yes. Peer pressure is a major factor.
• Protection: Develop strong willpower, avoid unsupportive peer groups, seek help from parents or trusted teachers, and engage in healthy extracurricular activities.

16. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit?

• Due to the addictive nature of these substances. Repeated use increases the tolerance level of receptors, requiring higher doses for the same effect. Abrupt discontinuation leads to 'withdrawal syndrome', driving the person back into the cycle of abuse.

17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?

• Motivations: Curiosity, adventure, stress (academic or social), peer pressure, and the perception of being 'cool'.
• Prevention: Avoid undue pressure on children, provide education and counselling, identify early warning signs, and ensure a supportive family environment.