Here are simplified step-by-step explanations of NCERT Solutions for Class 12 Science Biology Chapter 8 “Human Health And Disease.” These solutions are highly favored among Biology students in Class 12 Science for their ease of understanding and usefulness in completing homework assignments and exam preparation. All questions and answers from Chapter 8 of the NCERT Book for Class 12 Science Biology are available here at no cost, aiding students in their studies. Page No 164: Question 1: What are the various public health measures, which you would suggest as safeguard against infectious diseases? ANSWER: Public health measures are preventive measures which are taken to check the spread of various infectious diseases. These measures should be taken to reduce the contact with infectious agents. Some of these methods are: (1) Maintenance of personal and public hygiene:It is one of the most important methods of preventing infectious diseases. This measure includes maintaining a clean body, consumption of healthy and nutritious food, drinking clean water, etc. Public hygienic includes proper disposal of waste material, excreta, periodic cleaning, and disinfection of water reservoirs. (2) Isolation: To prevent the spread of air-borne diseases such as pneumonia, chicken pox, tuberculosis, etc., it is essential to keep the infected person in isolation to reduce the chances of spreading these diseases. (3) Vaccination: Vaccination is the protection of the body from communicable diseases by administering some agent that mimics the microbe inside the body. It helps in providing passive immunizationto the body. Several vaccines are available against many diseases such as tetanus, polio, measles, mumps, etc. (4) Vector Eradication: Various diseases such as malaria, filariasis, dengue, and chikungunya spread through vectors. Thus, these diseases can be prevented by providing a clean environment and by preventing the breeding of mosquitoes. This can be achieved by not allowing water to stagnate around residential areas. Also, measures like regular cleaning of coolers, use of mosquito nets and insecticides such as malathion in drains, ponds, etc. can be undertaken to ensure a healthy environment. Introducing fish such as Gambusia in ponds also controls the breeding of mosquito larvae in stagnant water. Page No 164: Question 2: In which way has the study of biology helped us to control infectious diseases? ANSWER: Various advancements that have occurred in the field of biology have helped us gain a better understanding to fight against various infectious diseases. Biology has helped us study the life cycle of various parasites, pathogens, and vectors along with the modes of transmission of various diseases and the measures for controlling them. Vaccination programmes against several infectious diseases such as small pox, chicken pox, tuberculosis, etc. have helped eradicate these diseases. Biotechnology has helped in the preparation of newer and safer drugs and vaccines. Antibiotics have also played an important role in treating infectious diseases. Page No 164: Question 3: How does the transmission of each of the following diseases take place? (a) Amoebiasis (b) Malaria (c) Ascariasis (d) Pneumonia ANSWER: Disease Causative organism Mode of transmission a. Amoebiasis Entamoeba histolytica It is a vector-borne disease that spreads by the means of contaminated food and water. The vector involved in the transmission of this disease is the housefly. b. Malaria Plasmodium sp. It is a vector-borne disease that spreads by the biting of the female Anopheles mosquito. c. Ascariasis Ascaris lumbricoides It spreads via contaminated food and water. d. Pneumonia Streptococcus pneumoniae It spreads by the sputum of an infected person. Page No 164: Question 4: What measure would you take to prevent water-borne diseases? ANSWER: Water-borne diseases such as cholera, typhoid, hepatitis B, etc. spread  by drinking contaminated water. These water-borne diseases can be prevented by ensuring proper disposal of sewage, excreta, periodic cleaning. Also, measures such as disinfecting community water reservoirs, boiling drinking water, etc. should be observed. Page No 164: Question 5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines. ANSWER: A ‘suitable gene’ refers to a specific DNA segment which can be injected into the cells of the host body to produce specific proteins. This protein kills the specific disease-causing organism in the host body and provides immunity. Page No 164: Question 6: Name the primary and secondary lymphoid organs. ANSWER: (a) Primary lymphoid organs include the bone marrow and the thymus. (b) Secondary lymphoid organs are the spleen, lymph nodes, tonsils, Peyer’s patches of small intestine, and appendix. Page No 164: Question 7: The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT (b) CMI (c) AIDS (d) NACO (e) HIV ANSWER: (a) MALT- Mucosa-Associated Lymphoid Tissue (b) CMI- Cell-Mediated Immunity (c) AIDS- Acquired Immuno Deficiency Syndrome (d) NACO- National AIDS Control Organization (e) HIV- Human Immuno Deficiency virus Page No 164: Question 8: Differentiate the following and give examples of each: (a) Innate and acquired immunity (b) Active and passive immunity ANSWER: (a) Innate and acquired immunity Innate immunity Acquired immunity 1. It is a non−pathogen specific type of defense mechanism. 1. It is a pathogen specific type of defense mechanism. 2. It is inherited from parents and protects the individual since birth. 2. It is acquired after the birth of an individual. 3. It operates by providing barriers against the entry of foreign infectious agents. 3. It operates by producing primary and secondary responses, which are mediated by BÂ−lymphocytes and T-lymphocytes. 4 It does not have a specific memory. 4 It is characterized by an immunological memory. (b) Active and passive immunity Active immunity Passive immunity 1. It is a type of acquired immunity in which the body produces its own antibodies against disease-causing antigens. 1. It is a type of acquired immunity in which readymade antibodies are transferred from one individual to another. 2. It has a long lasting effect. 2. It does not have long lasting effect. 3. It is slow. It takes time in producing antibodies and giving responses. 3. It is fast. It provides immediate relief. 4. Injecting microbes through vaccination inside the body is an example of active immunity. 4. Transfer of antibodies present in the mother’s milk to the infant is an example of …
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