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Table of Contents
NCERT Solutions for Class 12 Biology Chapter : 8 Human Health and Disease
Question 1.
What are the various public health measures, which you would suggest as a safeguard against infectious diseases?
Solution:
Prevention and control of infectious diseases
I. For water-borne diseases like typhoid, amoebiasis, etc.
Practice personal and public hygienic measures.
a. Personal hygienic measures
- Keeping the body clean
- Consumption of clean drinking water
- Eating fresh food
b. Public hygienic measures
- Proper disposal of waste and excreta
- Periodic cleaning and disinfection of water reservoirs, pool, tank etc.
II. For air-borne diseases like common cold, pneumonia
- Avoid close contact with infected persons.
- Avoid the use of belongings of the infected persons.
III. For vector-borne diseases like malaria
- Control and eliminate the vectors and their breeding places
- Introducing larvivorous fishes like Gambusia in ponds that feed on the larvae of the mosquito
- Avoid stagnation of water around the residential area.
- Spraying of insecticides in ditches, drainage areas, etc.
- Protection from a mosquito bite. Use mosquito nets in the doors and windows to prevent the entry of mosquitoes. It is very important in the light of recently widespread diseases like dengue fever, chikungunya etc.
The use of vaccines and immunization programmes has enabled us to eradicate smallpox. Diseases like polio, diphtheria, tetanus etc. have been controlled to an extent by the use of vaccines. Nowadays biotechnology is focussing on the preparation of newer and safer vaccines. A large number of antibiotics are available to treat many infectious diseases.
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 developed as we have come to know about 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 helps us to eradicate these diseases.
→ Biotechnology has helped in the preparation of developed and safe drugs and vaccines.
→ Antibiotics have also played a major role in the treatment of various infectious diseases.
3. How does the transmission of each of the following diseases take place?
(a) Amoebiasis (b) Malaria (c) Ascariasis (d) Pneumonia
Answer
(a) Amoebiasis: It is a vector transmitted disease that spreads by the means of contaminated food and water. The vector involved in the transmission of this disease is the housefly. Its mode of transmission is Entamoeba histolytica.
(b) Malaria: It is a vector transmitted disease that spreads by the biting of the female Anopheles mosquito. Its mode of transmission is Ascaris lumbricoides.
(c) Ascariasis: It spreads through contaminated food and water. Its mode of transmission is Ascaris lumbricoides
(d) Pneumonia: It spreads by the sputum of a diseased person. Its mode of transmission is Streptococcus pneumoniae,
Question 4.
What measure would you take to prevent water-borne diseases?
Solution:
Water-borne diseases can be prevented by drinking clean water. Water should be free from contamination, suspended and dissolved substances. If water is contaminated it should be boiled and filtered before drinking. Periodic cleaning and disinfection of water reservoirs, pools, and tanks should be done.
Question 5.
Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
Solution:
‘A suitable gene’ means the gene which is able to produce antigenic polypeptides of the pathogen in bacteria and yeast. Using recombinant DNA technology, it is possible to produce vaccines in large scale for immunisation. Hepatitis B vaccine is produced using this technology.
Question 6.
Name the primary and secondary lymphoid organs.
Solution:
Primary lymphoid organs are bone marrow and thymus. Secondary lymphoid organs are the spleen, lymph nodes, tonsils, Peyer’s patches of the small intestine, and mucosa-associated lymphoid tissues (MALT).
Question 7.
The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form.
- MALT
- CMI
- AIDS
- NACO
- HIV
Solution:
- MALT – Mucosal-associated lymphoid tissue.
- CMI – Cell-Mediated Immunity
- AIDS – Acquired Immuno Deficiency Syndrome
- NACO – National AIDS Control Organisation
- HIV – Human immunodeficiency virus.
(a) Innate and acquired immunity (b) Active and passive immunity
Answer
(a) Innate and acquired immunity
| Innate immunity | Acquired immunity |
| (i) It is a non-pathogen specific type of defense mechanism. | (i) It is a pathogen specific type of defense mechanism. |
| (ii) It is inherited from parents and protects the individual since birth. | (ii) It is acquired after the birth of an individual. |
| (iii) It operates by providing barriers against the entry of pathogenic agents. | (iii) It produces primary and secondary responses, which are mediated by B-lymphocytes and T-lymphocytes. |
| (iv) It does not specific memory. | (iv) It is observed by an immunological memory. |
(b) Active and passive immunity
| Active immunity | Passive immunity |
| (i) It is a type of acquired immunity in which the body produces its own antibodies against disease-causing antigens. | (i) It is a type of acquired immunity in which readymade antibodies are transferred from one person to another. |
| (ii) It shows long lasting effect. | (ii) It does not have long lasting effect. |
| (iii)It is slow. It takes time in producing antibodies and giving responses. | (iii) It is fast. It provides immediate respose. |
| (iv) Injecting microbes through vaccination inside the body is an example of active immunity. | (iv) Transfer of antibodies present in the mother’s milk to the infant is an example of passive immunity. |
9. Draw a well-labelled diagram of an antibody molecule.
Answer
Answer
AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV).
This is transmitted by following modes –
(a) Unprotected sexual contact with a diseased person.
(b) Transfusion of blood from a healthy to a diseased person.
(c) Sharing infected needles or syringes.
(d) infected mother to a child through the placental connection.
11. What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
Answer
→ AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV) via sexual or blood to blood contact.
→ After entering the human body, the HIV virus attacks and enters into the macrophages. Inside the macrophages, the RNA of the virus replicates with the help of enzyme reverse transcriptase and gives rise to viral DNA copy.
→ Then, this viral DNA incorporates into the host DNA and directs the synthesis of virus particles. → At the same time, HIV enters helper T- lymphocytes. It replicates and produces viral progeny.
→ These newly formed progeny viruses get released into the blood, attacking other healthy helper T-lymphocytes in the body.
→ As a result, the number of T-lymphocytes in the body of an infected person decreases in number, which causes decrease in immunity of person.
12. How is a cancerous cell different from a normal cell?
Answer
| Normal cell | Cancerous cell |
| (i) Normal cells show the property of contact inhibition. Therefore, when these cells come into contact with other cells, they stop dividing. | (i) Cancerous cells lack the property of contact inhibition. Therefore, they continue to divide, thereby forming a mass of cells called tumor. |
| (ii) They undergo differentiation after attaining a specific growth. | (ii) They do not undergo differentiation. |
| (iii) These cells remain confined at a particular location. | (iii) These cells do not remain confined at a particular location. They move into neighboring tissues and disturbs the functioning. |
13. Explain what is meant by metastasis.
Answer
The property of metastasis is perfomed by malignant tumors. These melingnent cells moves through different part of body by a pathological process. These cells divide uncontrollably, forming a mass of cells called tumor. From the tumor, some cells get shed off and enter into the blood stream. From the blood stream, these cells reach distant parts of the body and therefore, start the formation of new tumors by dividing actively.
14. List the harmful effects caused by alcohol/drug abuse.
Answer
Alcohol and drugs have several adverse effects on the individual, his family, and the society.
(i) Effects of alcohol:
→ Effects on the individual: Alcohol is injurious to the health of the individual. When an individual consumes excess alcohol, it causes damage to the liver and the central nervous system. As a result, other symptoms such as depression, fatigue, aggression, loss of weight and appetite may also be observed in the individual. Sometimes, extreme levels of alcohol consumption may also lead to heart failure, resulting coma and death. The immediate adverse effects of alcohol abuse are manifested in form of reckless bhehaviour, vandalism and voilence,Also, it is advisable for pregnant women to avoid alcohol as it may inhibit normal growth of the baby.
→ Effects on the family: Consumption of excess alcohol by any family member can have devastating effects on the family. It leads to several domestic problems such as quarrels, frustrations, insecurity, etc.
Effects of alcohol on society-
(a) Rash behaviour
(b) Malicious mischief and violence
(c) Disturbing social network
(d) Loss of interest in social activities, loss of interests in hobbies,change in eating and sleeping habites etc.
(ii) Effects of drugs: An individual who is addicted to drugs creates problems not only for himself but also for his family.
→ Effects on the addited individual: Drugs have an adverse effect on the central nervous system of an individual. This leads to the malfunctioning of several other organs of the body such as the kidney, liver, etc. The spread of HIV is most common in these individuals as they share common needles while injecting drugs in their body. Drugs have long-term side effects on both males and females. These side effects include increased aggressiveness, mood swings, and depression
→ Effects on the family and society: A person addicted to drugs creates problems for his family and society. A person dependant on drugs becomes frustrated, irritated, and anti-social.At the time of drug addicted becomes mental and financial distress.
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?
Answer
Yes, friends can influence one to take drugs and alcohol. A person can take the following steps for the prevention of themself against drug abuse:
→ by avoiding undue peer pressur as everyone has theire own field of interest which shouid be respected by theire teachers and family. One should not experiment with alcohol for curiosity and fun.
→ Avoid the company of friends who take drugs.
→ Seek help from parents and peers.a child should not pushed beyond his/her threshold limits.
→ Take proper knowledge and counseling about drug abuse. Devote your energy in other extra-curricular activities.
→ Seek immediate professional and medical help from psychologists and psychiatrists if symptoms of depression and frustration become apparent.
→ Get rid of the problems completely and lead a perfectly normal life by increasing their will power.
16. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
Answer
This question should be discussed with your subject teacher.
17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
Answer
→ Various factors are responsible for motivating youngsters towards alcohol or drugs. Curiosity, need for adventure and excitement, experimentation for fun are the initial causes for motivating youngsters.
→ Some youngsters start consuming drugs and alcohol in order to overcome negative emotions (such as stress, pressure, depression, frustration) and to excel in various fields..such youngsters use to abuse alcohol due to their family pressure for academics .
→ Several mediums like television, internet, newspaper, movies promote various brend by the brand ambassadors like celebrities . Celebrities are also ideal of youngsters so the get much infiuenced by them.
→ Amongst these factors, reasons such as unstable and unsupportive family structures and peer pressure can also lead an individual to be dependant on drugs and alcohol.
Preventive measures against addiction of alcohol and drugs:
(i) Parents should motivate and try to increase the will power of their child.
(ii) Parents should educate their children about the ill-effects of alcohol. They should provide them with proper knowledge and counselling regarding the consequences of addiction to alcohol.
(iii) It is the responsibility of the parent to discourage a child from experimenting with alcohol. Youngsters should be kept away from the company of friends who consume drugs.
(iv) Children should be encouraged to devote their energy in other extra- curricular and recreational activities.
(v) Proper professional and medical help should be provided to a child if sudden symptoms of depression and frustration are observed.
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