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Question 6:

Name the primary and secondary lymphoid organs.


(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.

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


(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

Question 8:

Differentiate the following and give examples of each:

(a) Innate and acquired immunity

(b) Active and passive immunity


(a) Innate and acquired immunity

Innate immunity

Acquired immunity


It is a non−pathogen specific type of defense mechanism.


It is a pathogen specific type of defense mechanism.


It is inherited from parents and protects the individual since birth.


It is acquired after the birth of an individual.


It operates by providing barriers against the entry of foreign infectious agents.


It operates by producing primary and secondary responses, which are mediated by B­−lymphocytes and T-lymphocytes.


It does not have a specific memory.


It is characterized by an immunological memory.

(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 has a long lasting effect.


It does not have long lasting effect.


It is slow. It takes time in producing antibodies and giving responses.


It is fast. It provides immediate relief.


Injecting microbes through vaccination inside the body is an example of active immunity.


Transfer of antibodies present in the mother’s milk to the infant is an example of passive immunity.

Question 9:

Draw a well-labelled diagram of an antibody molecule.


Question 10:

What are the various routes by which transmission of human immunodeficiency virus takes place?


AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV).

It has the following modes of transmission:

(a) Unprotected sexual contact with an infected person.

(b) Transfusion of blood from a healthy to an infected person.

(c) Sharing infected needles and syringes.

(d) From an infected mother to a child through the placenta.

Question 11:

What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?


AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV) via sexual or blood-blood contact. After entering the human body, the HIV virus attacks and enters the macrophages. Inside the macrophages, the RNA of the virus replicates with the help of enzyme reverse transcriptase and gives rise to viral DNA. 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 there. 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 progressively, thereby decreasing the immunity of a person.

Question 12:

How is a cancerous cell different from a normal cell?


Normal cell

Cancerous cell


Normal cells show the property of contact inhibition. Therefore, when these cells come into contact with other cells, they stop dividing.


Cancerous cells lack the property of contact inhibition. Therefore, they continue to divide, thereby forming a mass of cells or tumor.


They undergo differentiation after attaining a specific growth.


They do not undergo differentiation.


These cells remain confined at a particular location.


These cells do not remain confined at a particular location. They move into neighboring tissues and disturb its function.

Question 13:

Explain what is meant by metastasis.


The property of metastasis is exhibited by malignant tumors. It is the pathological process of spreading cancerous cells to the different parts of the body. These cells divide uncontrollably, forming a mass of cells called tumor. From the tumor, some cells get sloughed off and enter into the blood stream. From the blood stream, these cells reach distant parts of the body and therefore, initiate the formation of new tumors by dividing actively.

Question 14:

List the harmful effects caused by alcohol/drug abuse.


Alcohol and drugs have several adverse effects on the individual, his family, and the society.

A. Effects of alcohol:

Effects on the individual: Alcohol has an adverse effect on the body of an individual. When an individual consumes excess alcohol, it causes damage to the liver and the 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. 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 on the society:

(a) Rash behavior

(b) Malicious mischief and violence

(c) Deteriorating social network

(d) Loss of interest in social and other activities

B Effects of drugs: An individual who is addicted to drugs creates problems not only for himself but also for his family.

Effects on the 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.

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Question 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, friends can influence one to take drugs and alcohol. A person can take the following steps for protecting himself/herself against drug abuse:

(a) Increase your will power to stay away from alcohol and drugs. One should not experiment with alcohol for curiosity and fun.

(b) Avoid the company of friends who take drugs.

(c) Seek help from parents and peers.

(d) Take proper knowledge and counseling about drug abuse. Devote your energy in other extra-curricular activities.

(e) Seek immediate professional and medical help from psychologists and psychiatrists if symptoms of depression and frustration become apparent.

Question 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.


Drug and alcohol consumption has an inherent addictive nature associated with euphoria and a temporary feeling of well-being. Repeated intake of drugs increases the tolerance level of the body’s receptors, leading to more consumption of drugs.

Question 17:

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


Many factors are responsible for motivating youngsters towards alcohol or drugs. Curiosity, need for adventure and excitement, experimentation are the initial causes of motivation. 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. Several mediums like television, internet, newspaper, movies etc. are also responsible for promoting the idea of alcohol to the younger generation. 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:

(a) Parents should motivate and try to increase the will power of their child.

(b) 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.

(c) 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.

(d) Children should be encouraged to devote their energy in other extra- curricular and recreational activities.

(e) Proper professional and medical help should be provided to a child if sudden symptoms of depression and frustration are observed.