Important Questions for CBSE Class 12 Biology Chapter 7 - Human Health and Disease 2024-25

Very Short Questions and Answers (1 Mark Question)

1. Name the diagnostic test which confirms typhoid.

Ans: The diagnostic test which confirms typhoid is the Widal test.

2. Name the two major groups of cells required to attain specific immunity.

Ans: B-lymphocytes and T-lymphocytes are the two major groups of cells required to attain specific immunity.

3. You have heard of many incidences of Chikungunya in our country. Name the vector of the disease.

Ans: Aedes mosquito is the name of the vector of the Chikungunya disease.

4. Breast-fed babies are more immune to diseases than bottle-fed babies. Why?

Ans: Breast-fed babies are more immune to diseases than bottle-fed babies because the mother​s milk consists of antibodies (Ig A) which are not available in the case of bottle-fed babies.

5. Name the pathogen which causes malignant malaria.

Ans: The pathogen which causes malignant malaria is Plasmodium falciparum.

6. Which microorganism is used to produce the hepatitis B Vaccine?

Ans: The microorganism which is used to produce the hepatitis B Vaccine is Yeast.

7. What is the reason for shivering in malarial patients?

Ans: The reason for shivering in malarial patients is the release of the toxic substance hemozoin when RBC ruptures, after sporozoite infection, and causes chilling and high fever.

8. When is a tumor referred to as malignant?

Ans: A tumor is referred to as malignant when it starts to grow rapidly and then invade & damage the surrounding of the normal tissues.

9. Why does an AIDS patient suffer from many infections?

Ans: AIDS patients suffer from many infections because, in AIDS patients, the immune system weakens greatly and is unable to fight against any infection.

10. Name two curable sexually transmitted diseases?

Ans: The two curable sexually transmitted diseases are Gonorrhoea & Syphilis.

11. Name the type of cells that produce antibodies?

Ans: B – lymphocytes are the type of cells that produce antibodies.

12. Give the scientific name of the causative germ of elephantiasis?

Ans: The scientific name of the causative germ of elephantiasis is Wuchereria bancrofti.

13. Name the fish that help in the eradication of mosquito larvae.

Ans: Gambusia is the fish that help in the eradication of mosquito larvae.

Short Questions and Answers (2 Marks Question)

1. Where are B-cells and T-cells formed? How do they differ from each other?

Ans: B-cells and T-cells are the lymphocytes that are formed in the bone marrow. The function of B-cells is to produce antibodies while the T-cells do not produce antibodies instead they help B-cells in producing antibodies.

2. Given below are the pathogens and the diseases caused by them. Which out of these pairs is not the correct matching pair and why?

(a) Wuchereria​ Filariasis

(b) Microsporum​ Ringworm

(c) Salmonella ​ Common Cold

(d) Plasmodium ​ Malaria

Ans: Salmonella: Common cold is not a matching pair because the common cold is a viral disease that is caused by a virus while Salmonella is a bacterium that causes bacterial disease in the intestinal tract of the body.

3. What would happen to the immune system, if the thymus gland is removed from the body of a person?

Ans: The thymus gland is responsible for the production and maturation of T-lymphocytes. If the thymus gland is removed from the body of a person, then the immune system of the person will become weak.

4. Lymph nodes are secondary lymphoid organs. Describe the role of lymph nodes in our immune response.

Ans: The role of lymph nodes in our immune response is to act as the site where the lymphocytes and the antigen interact with each other. The immune system of the person got responsive when the microorganisms enter the lymph nodes resulting in the activation of the lymphocytes present there.

5. What is the role of histamine in inflammatory response? Name few drugs which reduce the symptoms of allergy.

Ans: Histamine is released by mast cells and they act as an allergy-mediator which causes the dilation of the blood vessels. The drugs which reduce the symptoms of allergy are Antihistamine steroids and adrenaline.

6. Differentiate between two different types of tumors?

Ans: The difference between two different types of tumors is:

7. What do you mean by withdrawal Symptoms? What are its characteristics?

Ans: Withdrawal symptoms are observed in the case of a drug addict where the body of a person shows characteristic unpleasant symptoms if they suddenly do not get the regular dose of the drug. The characteristics symptoms include anxiety, sweating, shakiness, depression, restlessness, muscular cramps, etc.

8. Differentiate between active & passive immunity?

Ans: The difference between active & passive immunity are:

9. Enumerate the two properties of cancer cells that distinguish them from normal cells.

Ans: The two properties of cancer cells that distinguish them from the normal cells are:

i) The cells undergo uncontrolled proliferation without any differentiation

ii) The cells can invade other tissues which are called metastasis.

10. What are allergens? How do they cause inflammatory responses inside the human body?

Ans: The allergens are the substances that cause the hypersensitive reaction of the immune system such as dust, pollen grains, etc. When the person is exposed to an allergen for the first time then no allergy is caused but if they get exposed to allergens frequently then the allergen combines with Ig E on the mast cell resulting in the bursting of the cells and release of Histamines which leads to the inflammatory response. Thus, allergens are said to be weak antigens.

11. What are autoimmune diseases? Give two examples?

Ans: Autoimmune diseases are those in which the immune system of the body gets disturbed ad starts to attack the healthy cells. Immunity is based on the ability to differentiate foreign organisms from self-cells. Sometimes the immune system may go off the track & turns against self-antigen and elicit immunity. Examples of autoimmune diseases are Rheumatoid arthritis and Myasthenia gravis.

Long Questions and Answers (3 Marks Questions)

1. What are Cannabinoids? From which plant Cannabinoids are obtained? Which part of the body is affected by consuming these substances?

Ans: Cannabinoids are a group of naturally occurring chemicals present in Cannabis and interact with Cannabinoid receptors present there.

- Cannabinoids are obtained from the plant Cannabis sativa mainly from their inflorescence.

- The part of the body which is affected adversely by consuming these substances is the cardiovascular system.

2. In the figure, the structure of an antibody molecule is shown. Observe it and answer the following questions.

(i) Label parts A, B, and C.

Ans: A - Antigen binding site, B - Light chain, C- Heavy chain.

(ii) Which cells produce these chemicals?

Ans: B – lymphocytes are the cells that produce these chemicals.

(iii) State the function of these molecules.

Ans: The function of antibodies is to provide an acquired immune response to the body.

3. Mention any three causes of drug abuse. Suggest some measures for the prevention and control of drug abuse.

Ans: Reasons to attract towards and cause drug abuse: Curiosity, escape from frustration and failure, peer pressure, false belief of enhanced performance, family problems. 

Preventive measures:

- Avoid undue peer pressure

- Education and Counselling

- Seeking help from parents and peers.

- Looking for danger signs

- Seeking professional and medical help

4. A person shows unwelcome immunogenic reactions while exposed to certain substances.

(a) Name this condition.

Ans: When a person shows unwelcome immunogenic reactions while exposed to certain substances is called allergy. 

(b) What common term is given to the substances responsible for this condition?

Ans: Allergens is the common term that is given to the substances responsible for the allergy.

(c) Name the cells and the chemical substances released which cause such reactions.

Ans: Mast Cells are the cells while ​Histamine and Serotonin are the chemical substances released which cause such reactions.

5. Fill in the blanks in the different columns of the table given below to identify the no’s 1 to 6.

Ans: The fill-in blanks in the different columns of the table given below to identify the no’s 1 to 6 are:

(i) Alveoli filled with fluid, reduced breathing, fever, chills, cough, and headache.

(ii) Salmonella typhi

(iii) Common Cold

(iv) Internal bleeding, muscular pain, anemia, fever, and blockage of the intestinal passage.

(v) Microsporum species/Trichophyton species/Epidermophyton Species.

(vi) Amoebiasis/amoebic dysentery

6. In the given flow diagram, the replication of retrovirus in a host cell is shown. Examine it and answer the following questions

(a) Why is a virus called retrovirus?

Ans: A virus is called retrovirus because it consists of RNA as genetic material and undergoes reverse transcription to produce DNA as in the case of HIV.

(b) Fill in (1) and (2)

Ans: 1: Viral DNA is produced by reverse transcriptase.

2: New Viral RNA is produced by the infected cell.

(c) Can infected cells survive while viruses are being replicated and released by the host cells?

Ans: Yes, the infected cell can survive while viruses are being replicated and released by the host cell.

7. What is innate immunity? List the four types of barriers that protect the body from the entry of foreign agents.

Ans: The immunity which is resent at the time of birth and shows a non-specific type of defense is called Innate Immunity.

The four types of barriers that protect the body from the entry of foreign agents are:

(i) Physical Barriers: Skin, digestive and urinogenital tract, mucous-coated epithelium, or respiratory.

(ii) Physiological Barriers: Acidity of Stomach, tears, sweat, lysozyme in saliva.

(iii) Cellular Barrier: Macrophages, monocytes neutrophils, and natural killer lymphocytes.

(iv) Cytokine Barriers: Interferons produced by Virally infected cells, protect the non-infected cells from further Viral infection.

8. How does the humoral immune system works when our body is infected?

Ans: The immunity in which antibodies are developed for attacking the microbes is called the Humoral immune response. The receptors are present on the surface of each B-cell that recognize a specific antigen. When the B-cell is exposed to antigens then it will result in triggering of B-cells to proliferate further thus leading to the formation of a large clone cell which continuous stimulation and then result in the increase in the number of B-lymphocytes which then differentiates into plasma cells that are smaller antibody-producing cells. Antibodies that are produced by each clone of plasma cells will react with their antigenic determinant and leads to the stimulation of the initial proliferation. The phagocytic cells digest the antigen-antibody complex which is formed when the antibody binds to the antigen. When plasma cells are exposed to the same antigen later then some of these plasma cells develop into memory cells.

9. It was diagnosed by a specialist that the Immune System of the body of a patient has been suppressed. Describe the infection and the mechanism of its proliferation in the body.

Ans: If the immune system of the patient has been suppressed then he is found to be suffering from the human immunodeficiency virus (HIV). The HIV enters into the helper T- cells & undergoes replication to produce progeny viruses. The replication of virus involves: -

(i)First viral capsid enters the cell where the reverse transcriptase enzyme will copy single-stranded RNA and convert it into complementary DNA.

(ii) The ribonuclease H degrades the RNA & the DNA strand becomes double-stranded DNA after its duplication.

(iii) Integrase enzyme is responsible for a complex sequence of reactions in which the Proviral DNA is integrated into cells’ DNA.

(iv) Virus becomes active once it has infected the cell resulting in the liberation of a large number of virus particles that can infect other cells.

10. What are carcinogens? What are the different types of carcinogens? Also, mention the different methods of treatment of cancer?

Ans: Carcinogens are the substances that cause cancer. These substances may be chemical or physical things like: -

1. Smoking

2. Tobacco chewing

3. Radiations e.g., UV- x-ray, cosmic rays.

4. Chemical agents.g., mustard gas, aflatoxin, cadmium oxide

5. Biological agents e.g., retroviruses

6. Cellular agents proto-oncogenes which when activated under certain conditions may lead to oncogenic transformation of cells.

Treatment of cancer involves: -

1. Surgery: - surgical removal of the tumor.

2. Chemotherapy: treatment with drugs that can destroy cancer cells.

3. Immunotherapy: interleukin, use of interferons, vaccines to generate non-specific defense mechanism.

4. Radiation Therapy: - therapy like x-ray or radiotherapy and the utilization of ionizing radiations that help to kill cancer cells.

5. Hormonal Suppression: providing or blocking certain hormones.

11. describe the ill – effects of drug abuse in males and females. also, mention the preventive measures that are to be taken to reduce such effects.

Ans: the ill-effects of drug abuse in males and females are:

1) ILL – Defects in Males: - increased aggressiveness, acne, decreased sperm production, mood swing depression reduction of the size of testicles, premature baldness, kidney, and liver dysfunction.

2) ILL – Effects in Females: - increased aggressiveness, masculinization, mood swings, excessive hair growth on the face and body, depression abnormal menstrual cycle, and deepening of the voice.

the preventive measures that are to be taken to reduce such effects are: -

1. Education and Counselling: - to accept failure as part of life, to face problems or stress, and to channel child’s energy to some health-promoting activities.

2. Avoid Undue Peer Pressure: - to pressurize a child to perform beyond his capabilities.

3. Seeking Help From Parents and Peers: - to share the feeling of anxiety and guilt.

4. Seeking Professional for Medical Help: - help available in the form of a highly qualified psychiatrist, psychologist, etc.

12. What is vaccination? What type of immunity is provided by vaccination?

Ans: The process of development of immunity with the help of vaccines taken in the body is called vaccination, here to produce immunity against a particular pathogen a weakened pathogen is injected into the body that results in the production of antibodies. The antibodies that are produced against these antigens would result in the neutralization of the pathogenic agent. The vaccine will startle the pathogen by producing a large number of antibodies and will also generate memory B – and T – cells that help in recognizing the pathogen quickly when they are exposed to them.

The type of immunity provided by vaccination is Active immunity. However, we need to directly inject the immunity to a patient’s body if a person is infected with some deadly microbe to which a quick immune response is required, this type of immunization is called Passive immunization.

13. (i) Differentiate between communicable and non – communicable diseases?

Ans: The difference between communicable & non – communicable diseases are:

(ii) Name the body part & the host in which the following events take place in the life cycle of plasmodium.

(a) Fertilization

Ans: Fertilization in the life cycle of plasmodium takes place in the gut of female anopheles.

(b) Development of Gametophyte

Ans: Development of Gametophyte in the life cycle of plasmodium takes place in RBCs of Human beings.

(c) Release of sporozoites

Ans: Salivary gland of female anopheles release of sporozoites.

(d) Asexual Reproduction.

Ans: Asexual Reproduction takes place in the liver cells of human beings.

Very Long Questions and Answers (5 Marks Questions)

1. Answer the following concerning Caner.

(a) How does a cancerous cell differ from a normal cell?

Ans: The growth and differentiation in normal cells are highly controlled and regulated (contact = inhibition) while in the case of cancerous cells they continue to divide giving rise to masses of cells (tumours) and have lost the property of contact inhibition.

(b) Benign tumour is less dangerous than a malignant tumour. Why?

Ans: Benign tumour is less dangerous than a malignant tumour because the benign tumour will be confined to only the affected organ and is enclosed in a connective tissue sheath and does not enter the metastatic stage.

(c) Describe the causes of cancer.

Ans: Cancer may be caused due to various carcinogens that include chemicals (Nicotine, Aflatoxin, Cadmium oxide, Asbestos), physical (radiations), and biological (viral oncogenes).

(d) mention two methods of treatment of the disease.

Ans: The methods of treatment of the disease are surgery, radiotherapy, chemotherapy.

2. The pathogen of a disease depends on the RBCs of humans for growth and reproduction. The person with this pathogen suffers from the chill and high fever.

(a) Name the disease.

Ans: Malaria is a disease where the pathogen of a disease depends on the RBCs of humans for growth and reproduction.

(b) Name the different species of Plasmodium. 

Ans: The different species of Plasmodium are Plasmodium. vivax, P. Malariae and P. falciparum.

(c) How malaria is caused?

Ans: Malaria is caused by the release of toxins (hemozoin) which is produced by the malarial parasite in the human body by the rupturing of RBCs in the blood.

(d) Represent the life cycle of the pathogen diagrammatically.

Ans: The life cycle of Plasmodium:

3. The immune system of a person is suppressed. He was found positive for a pathogen in the diagnostic test ELISA.

(a) Name the disease, the patient is suffering from.

Ans: When the immune system of a person is suppressed then the person is found to be suffering from AIDS (Acquired Immunodeficiency Syndrome).

(b) Which pathogen is identified by the ELISA test?

Ans: HIV (Human Immunodeficiency Virus) pathogen is identified by ELISA test.

(c) Which cells of the body are attacked by the pathogen?

Ans: Helper T-cells, macrophages, B-lymphocytes are cells of the body that are attacked by the pathogen.

(d) Suggest preventive measures of the infection.

Ans: Preventive measures of the infection are:

(i) People should be educated about AIDS transmission.

(ii) Disposable needles and syringes should be used

(iii) Sexual habits should be changed immediately

(iv) High-risk groups should be discouraged from donating blood.

(v) Routine screening may be done.

4. Discuss the role of lymphoid organs in the immune response. Explain the different types of lymphoid organs giving two examples of each type in humans.

Ans: the role of lymphoid organs in the immune response is the origin, maturation & proliferation of lymphocytes. these lymphoid organs are of two types: -

1. Primary Lymphoid Organ: - they are sensitive lymphocytes in which the immature lymphocytes differentiate into antigens. it consists of: -

(a) Bone Marrow: – it is the main lymphoid organ where all types of blood cells including lymphocytes are formed and are present in the thigh region. it helps in the development & maturation of b – cells by providing a micro-environment.

(b) Thymus: - it is located beneath the chest bone near the heart. it helps in the development & maturation of t – lymphocytes by providing a microenvironment.

2. Secondary Lymphoid Organ: - they help the lymphocytes to interact with the antigen which results in the proliferation leading to the formation of effector cells. it includes.

(a) Spleen: - it is a large bean-shaped organ that consists of lymphocytes & phagocytes. it is called the graveyard of rbcs and thus acts as a filter of blood by trapping blood–bound microorganisms.

(b) Lymph Node: - they are small – solid structures and are part of the lymphatic systems that are located at different points. its main role is to trap the antigens that try to enter into lymph & tissue fluid. these antigens will result in the activation of lymphocytes.

5. With the help of a well–labeled diagram, Describe the life cycle of malarial parasite.

Ans: Malaria is a protozoan disease caused by plasmodium vivax. It has two hosts – female anopheles which acts as the vector of plasmodium and man that acts as the primary host where the parasite maintains an amoeboid stage in RBCS & later produces gametophyte.

The life cycle of plasmodium involves the following steps: -

• In humans malaria is caused by Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium knowlesi.

• Malaria parasite life cycle in humans is of four-phase- pre-erythrocytic schizogony phase, erythrocytic schizogony phase, gametogenic phase, and exoerythrocytic schizogony phase.

• Sporozoites of malaria are present in the salivary gland of mosquitoes and transmitted to humans by mosquito bites where sporozoites are introduced into the blood.

• The development phase of malaria sporozoites takes place in the liver of humans where multiple nuclear divisions develop schizont containing numerous merozoites.

• Numerous merozoites are released and enter red blood cells by the receptor for merozoites in the glycoprotein.

• Malaria disease’s first onset appears after the incubation period of 9-14 days, where patients may not appear to be ill.

• The common symptoms of malaria disease are- fever, headache, chills, and vomiting appear for up to 10-15 days after the person is infected by the malaria parasite.

6. What do you mean by “Outbreeding”. What are the different methods employed for outbreeding?

Ans: Outbreeding is the process where the breeding between unrelated male & female animals takes place. It can be done in the following ways: -

1. Out Cross: - the outcross is the process of the mating of animals that are of the same breed but for 4-6 generations of their pedigree, they do not have any common ancestor. for those animals that have a below-average in growth rate of beef cattle, milk production, etc, it is the best method of breeding animals.

2. Cross–Breeding: - the breeding between the superior males of one breed & superior females of another breed is called cross-breeding. by this breeding technique, the desirable qualities of two different breeds can be combined which is then used for commercial production e.g., the formation of hisardale, a new breed of sheep is developed by crossing bikaneri ewes & marino rams.

3. Interspecific Hybridisation: - it is the cross where the breeding occurs in between the male & female animals of two different related species, resulting in the progeny which is a combination of desirable features of both parents e.g., the mule is produced by the cross between donkey & a female horse.

7. What is somatic hybridization – Explain the steps involved in the production of somatic hybrids?

Ans: The process of fusion of two protoplasts from the somatic cells of two different varieties or species of a plant under sterile on a suitable nutrient culture medium condition is called Somatic hybridization. For example, tomato which is produced by fusion of protoplast of tomato & potato is a somatic hybrid.

The steps involved in the production of somatic hybrids are: -

1. First the protoplasts from two different varieties of plants are isolated that are having a desirable character.

2. The cytoplasm of two protoplasts then undergoes fusion resulting in the mixing of cytoplasm. In this fusion, even after fusion of cytoplasm the nuclei of two protoplasts may or may not fuse. The fusion here requires a suitable agent called fusogenic, PEG, or polyethene glycol.

3. The hybrid protoplast produced will then synthesize a new cell wall around it under favourable conditions. This hybrid cell will act as a single cell & later undergo division that results in the formation of callus.

4. The callus which is regenerated is then transferred to a new culture plate that contains the suitable culture media. In this culture media, the callus divides and then results in the formation of roots and shoots by the process of organogenesis.

Class 12 Biology Chapter 7 Important Questions- Summary

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Class 12 Biology Chapter 7 Important Questions- Summary

Types of Diseases

The body of a human tends to suffer from many kinds of infections and diseases and that might be because of genetic defects or an unhealthy lifestyle. These diseases can be classified into two different categories:

1. Congenital Diseases: Presence of genetic abnormalities from the time of birth. These kinds of diseases might occur due to mutation of the gene, chromosomal aberration, or effects on the environment. In such diseases, the next generation might get affected by chromosomal and gene defect transmission. Haemophilia, Turner's disease, colour blindness, Down syndrome, etc. are some of the examples.

2. Acquired Diseases: These are the kinds of diseases that have been acquired during the lifetime of a person. The types of acquired diseases are Infectious or communicable disease, Non-communicable disease, Deficiency disease, and Allergies.

• The pathogen can be defined as the organism which is responsible for causing disease. Examples of the same may include, viruses, bacteria, fungi, protozoa, worms, and others. The entry of such pathogens inside the body can occur in multiple ways.

Immunity 

Immunity is called the capacity of the body to defend and fight against any foreign body or pathogen. Our body is protected by the help and working of the immune system against any infection

Two kinds of immunity are found:

• Innate immunity: It is the kind of immunity that is present from the time of birth. In our body's defense system, there are four kinds of barriers that help in protecting the body against any infection or disease. These barriers include- Physical barriers, Physiological barriers, Cellular barriers, and Cytokine barriers.

• Acquired immunity: It is the kind of immunity that is acquired during the lifespan and is pathogen-specific. After the first contact with a pathogen, the low-intensity primary response is initiated. Later infection, due to first response memory, results in a strongly amplified secondary response or anamnestic response.

AIDS (Acquired Immuno- Deficiency Syndrome)

• AIDS is caused due to the virus, named HIV which stands for Human Immunodeficiency Virus.

• It is a retrovirus, with its genome being RNA.

• The virus, via the enzyme reverse transcriptase, generates viral DNA in the host.

• In the host genome, the viral DNA is incorporated and multiple copies of the virus are made.

• The virus enters T-cells, where it reproduces and multiplies, causing the number of T lymphocytes to decrease significantly.

Cancer

• The main reason for cancer is uncontrolled cell division which ultimately leads to tumour development.

• There is a failure of the regulatory system in the oncogenic transformation of the normal cells.

• These Cancerous cells are observed to lack the property of contact inhibition, which prevents further cell growth when they come into contact with other types of cells.

• Benign tumours and Malignant tumours are the types of tumours observed.

Drugs and Alcohol Abuse

• The widely abused drugs may include heroin, cannabinoids, and coca alkaloids.

• Some opioid receptors exist in the CNS and GI tract, where opioid drugs are found to get bound.

• A popularly known heroin or smack, named Diacetylmorphine is derived from the latex of Papaver somniferum, a poppy plant. It is extracted by morphine acetylation.

• Cannabinoids bind to the receptors of cannabinoids which are found in the brain.

• From the top of the flower, resins, leaves, of the Cannabis sativa plant, cannabinoids, such as, marijuana, charas, hashish, ganja, and others are obtained.

• Cocaine also called coca alkaloid is derived from the plant Erythroxylum coca. 

• Cocaine functions by dealing with the transport of dopamine which is also a neurotransmitter.

• To increase their performance, muscle relaxation and decrease anxiety, sportsmen often take cannabinoids.

• For the purpose of relieving pain and inducing sedatives, morphine is used.

• As a medicine for depression, anxiety, and other mental disorders, barbiturates, benzodiazepines, amphetamines, etc. are included.

• The nicotine (alkaloid) found in tobacco activates the adrenal gland to release adrenaline and noradrenaline hormones.

Conclusion

Class 12 biology chapter 7 important questions have covered and summed up all the crucial points at a single platform in the form of a pdf. Here in this chapter, we discussed Types of Diseases, Immunity, types of immunity, Acquired ImmunoDeficiency Syndrome, Cancer, and Drugs and Alcohol Abuse. These topics are highly important from the exam view and one can prefer this document for easy learning of the chapter.

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