The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 12 Biology Chapter 8, "Human Health And Disease" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
01. What are the various public health measures, which you would suggest as safeguard against infectious diseases?
Ans. In truth, laws and regulations of public health in respect of fight against infectious diseases belong to the following categories:
Maintenance of personal and public hygiene: This is a basic approach in the prevention of most communicable diseases. This measures comprises of keeping oneself clean, eating healthy and balanced diets, taking clean water, etc. Philloney public hygiene there is proper segregation and treatment of waste and defecation, regular sanitation of the community, and cleansing of the water systems.
Isolation: People who have contracted infectious diseases which are transmitted through the air such as pneumonia, chicken pox or tuberculosis need to be kept apart from other people as a reasonable measure to control the spread of such infections.
Vaccination: It is the process of conferring immunity on an individual from infectious diseases by the introduction of an agent which tends to reproduce the micro-organism within the individual’s body. It is thus useful in giving the suffering body some passive immunity from the virus. Against many other diseases,specific vaccines are available, such as those protecting against tetanus, polio, measles, mumps, etc;
Vector Eradication: Some diseases such as malaria, filariasis and diseases like dengue and chikungunya are diseases which spread to the human body through vectors. Hence, these diseases can be avoided by making the environment clean and HVAC prevention of mosquitoes’ reproduction as cases. They do include not permitting water to pool around openly used spaces. Also, measures like periodic cleaning of coolers, use of mosquito nets and spreading of insecticides 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 still water against diseases.
02. In which way has the study of biology helped us to control infectious diseases?
Ans. Pathology is the branch of science that focuses on the study of diseases. In a broader context, it also encompasses diagnostic, preventive, and therapeutic measures. While pathology examines various types of diseases, we will specifically focus on those caused by pathogenic organisms. This includes understanding the host's reactions, which manifest as symptoms, diagnosing these conditions through symptom analysis, exploring the etiology of the pathogens, and outlining the steps taken to treat the host by eliminating or, when necessary, managing the pathogen. Thus, the study of biology has significantly contributed to our ability to control infectious diseases.
03. Hovy does the transmission of each of the following diseases take place?
(a)Amoebiasis (b) Malaria
(c)Ascariasis (d) Pneumonia
Ans. (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 pneumonia
04. What measure would you take to prevent water-borne diseases?
Ans. Drinking contaminated water is a major cause of waterborne diseases like typhoid and cholera. To prevent these illnesses, it's important to dispose of sewage and waste properly. We should also regularly check our water sources and ensure we boil water before drinking it.
05. Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
Ans. A 'suitable gene' is a particular segment of DNA that can be introduced into the cells of a host organism to create specific proteins. These proteins target and eliminate disease-causing organisms within the host, thereby offering immunity.
06. Name the primary and secondary lymphoid organs.
Ans. Primary lymphoid organs – Bone marrow and thymils.
Secondary lymhoid organs – Spleen, lymph nodes, tonsils.
07. The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its fall form:
(a) MALT
(b) CMI
(c) AIDS
(d)NACO
(e) HIV
Ans. (a) MALT- Mucosa-Associated Lymphoid Tissue
(b) CMI- Cell-Mediated Immunity
(c) AIDS- Acquired Immune Deficiency Syndrome
(d) NACO- National AIDS Control Organization
(e) HIV- Human Immune Deficiency virus
08. Differentiate the following and give examples of each:
(a) Innate and acquired immunity
(b)Active and passive immunity
Ans. a) Innate and acquired immunity
Innate Immunity | Acquired immunity |
It is inherited from parents and protects the individual since birth. | Developed after birth of child during one’s own life |
It is inherited from parents | Not inherited from parents |
Innate immunity is not acquired from any previous attack of disease | Acquired in response to a disease or after being vaccinated |
b) Active and passive immunity
Active immunity | Passive immunity |
It is a type of acquired immunity in which the body produces its own antibodies against disease-causing antigens. | It is a type of acquired immunity in which readymade antibodies are transferred from one individual to another. |
It doesn’t have any side effects | It may have side effects |
Long lasting | Have a short span |
It takes a long period to provide relief | It immediately provide relief |
09. Draw a well-labelled diagram of an antibody molecule.
Ans.
10. What are the various routes by which transmission of human immunodeficiency virus takes place?
Ans. Various routes by which transmission of human immunodeficiency virus takes place are
(i) Illicit sexual contact.
(ii) Sexual contact with multiple partners.
(iii) Transfusion of the blood of infected person.
(iv) Intravenous drug users that shares needles are at high risk of contracting AIDS.
11. What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
Ans. AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which spreads through sexual contact or blood-to-blood transmission. Once the virus enters the human body, it targets and infects macrophages. Inside these cells, the virus's RNA is replicated with the help of an enzyme called reverse transcriptase, leading to the formation of viral DNA. This viral DNA then integrates into the host's DNA, instructing the cell to produce new virus particles. Simultaneously, HIV also infects helper T-lymphocytes, where it replicates and generates new viral offspring. These newly created viruses are released into the bloodstream, where they go on to attack other healthy helper T-lymphocytes. Consequently, the number of T-lymphocytes in an infected individual declines over time, resulting in a weakened immune system.
12. How is a cancerous cell different from a normal cell?
Ans.
| Normal Cells | Cancerous Cells |
|---|
| 1. Contact inhibition: Normal cells stop dividing when they come into contact with other cells. | 1. Lack of contact inhibition: Cancerous cells do not stop dividing, leading to the formation of a mass of cells or a tumor. |
| 2. Differentiation: Normal cells mature and perform specific functions after reaching a certain size. | 2. No differentiation: Cancerous cells do not mature or perform specific functions. |
| 3. Confined location: Normal cells stay in one place within the body. | 3. Spread to other areas: Cancerous cells can move to nearby tissues, disrupting their function |
13. Explain what is meant by metastasis.
Ans. Metastasis refers to the process where cancer cells, due to uncontrolled growth, spread to other parts of the body via bodily fluids, leading to the formation of secondary tumors. This characteristic is only seen in malignant tumors.
14. List the harmful effects caused by alcohol/drug abuse.
Ans. The harmful effects of alcohol abuse include:
(i) Alcohol produces more energy primarily as heat, but it also causes blood vessels to dilate. As a result, the heat generated is quickly lost. Continuous dilation can make the arterial walls brittle and rigid over time. These changes in blood vessel properties, along with the accumulation of fatty deposits from alcohol, can negatively impact heart function.
(ii) Alcoholism can lead to conditions such as gastric ulcers and gastritis.
(iii) In cases of chronic alcoholism, nerve axons can become inflamed, resulting in neuritis.
(iv) The liver can suffer permanent damage due to fat accumulation, leading to a condition known as cirrhosis, where the liver becomes dry and hardened.
The harmful effects of drug abuse include:
(i) Overdosing on drugs can result in coma and death, often due to respiratory failure, heart failure, or cerebral hemorrhage.
(ii) Individuals may show a lack of interest in personal hygiene, experience withdrawal, isolation, depression, fatigue, and exhibit aggressive or rebellious behavior.
(iii) Those who use intravenous drugs are at risk of contracting serious infections such as AIDS and hepatitis B.
(iv) The negative consequences of drug use can manifest as reckless behavior, vandalism, and violence.
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?
Ans. Yes, friends can definitely influence someone to use drugs and alcohol. Here are some steps a person can take to protect themselves from drug abuse:
Strengthen your willpower to resist alcohol and drugs. It's important not to experiment with alcohol out of curiosity or for fun.
Steer clear of friends who use drugs.
Reach out for support from parents and peers.
Educate yourself about drug abuse and seek counseling if needed. Channel your energy into other extracurricular activities.
If you notice signs of depression or frustration, don't hesitate to seek immediate help from psychologists or psychiatrists.
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.
Ans. Once a person begins consuming alcohol or drugs, breaking free from that habit can be incredibly challenging. They often believe that alcohol is the only way to feel normal. Additionally, there are physical and psychological factors that create resistance to quitting. Prolonged alcohol use can lead to such a strong addiction that a person's nervous system only functions properly in the presence of alcohol or drugs, making it difficult for them to live a normal life without these substances.
17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
Ans. It suggests that human beings must have been using mind-affecting drugs right from the bare beginnings of prehistory. Man is addicted to drugs, smoking and drinking because he cannot make mental adjustment with stresses & strains, drudgery, extreme misery in daily life. Until we can find a better way to handle this serious situation and take the edge off, humans have resorted broadly to stimulants, depressents of all colors AND hallucengens. Stimulants: Accelerates body processes; depressant slows them down. Hallucinogens change what a person thinks, feels or sees.
What Parents Can Do to Prevent Drug Abuse could be:
(i) Communicate openly with the children, listen to their problems patiently and teach them how to handle the problems.
(ii) Take interest in children’s activities and their friends circle.
(iii) Set an example for children by not taking drugs or alcohol.
(iv) Keep track of prescribed drugs in home.
(v) Learn as much as possible about drugs.
