Unseen Passage

For Class 4 to Class 12

Human Health and Diseases Class 12 Biology Important Questions

Please refer to Human Health and Diseases Class 12 Biology Important Questions with answers below. These solved questions for Chapter 8 Human Health and Diseases in NCERT Book for Class 12 Biology have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these solved problems properly as these will help them to get better marks in your class tests and examinations. You will also be able to understand how to write answers properly. Revise these questions and answers regularly. We have provided Notes for Class 12 Biology Important Questions for all chapters in your textbooks.

Important Questions Class 12 Biology Chapter 8 Human Health and Diseases

Objective Type Questions

Question. Which of the following acts as mechanical carrier of amoebiasis?
(A) Mosquito
(B) House fly
(C) Pig
(D) Human



Question. Ascaris belongs to
(A) Protozoan
(B) Coelentrata
(C) Aschelminthes
(D) Annelida



Question. Symptoms of ascariasis are
(A) Internal bleeding
(B) Muscular pain
(C) Anaemia and blockage of intestinal path
(D) All of these



Question. Elephantiasis is a common name for which disease
(A) Ascariasis
(B) Filariasis
(C) Amoebiasis
(D) None of these



Question. Elephantiasis is characterized by
(A) Chronic inflammation in lymphatic vessels of lower limb
(B) Internal bleeding
(C) Often gross deformities in genital organs
(D) Both (A) and (C)



Question. Microsporum is the causal agent of which disease
(A) Ascariasis
(B) Filarisis
(C) Ringworm
(D) Amoebiasis



Question. Ring worm infection is caused by
(A) Mosquito bite
(B) Eating contaminated food
(C) Using comb, towel or clothes of infected person
(D) Nasal discharge droplets of infected person



Question. Which of the disease is not spread by contaminated food and water?
(A) Typhoid
(B) Ring worms
(C) Amoebiasis
(D) Ascariasis



Question. Which of the following disease is not spread by insect vector?
(A) Malaria
(B) Chikungunya
(C) Filaria
(D) All of these are spread by insects



Question. Elephantiasis is caused by which pathogen?
(A) Plasmodium vivax
(B) Wuchereria malayi
(C) Microsporum
(D) Epidermophyton



Question. The organisms which cause diseases in plants and animals are called
(A) Pathogens
(B) Vectors
(C) Insects
(D) Worms



Question. Which type of immune response is responsible for the rejection of tissues/organs in the patient’s body post transplantation ?
(A) auto-immune response
(B) humoral immune response
(C) physiological immune response
(D) cell-mediated immune response



Question. Opium is obtained from :
(A) Papaver somniferum
(B) Cannabis sativa
(C) Erythroxylum coca
(D) Datura metel



Question. The chemical test that is used for diagnosis of typhoid is
(A) ELISA-Test
(B) ESR-Test
(C) PCR-Test
(D) Widal-Test



Question. Tobacco consumption is known to stimulate secretion of adrenaline and nor-adrenaline. The component causing this could be
(A) Nicotine
(B) Tannic acid
(C) Curamin
(D) Catechin



Question. Which compound is formed by acetylation of morphine ?
(A) Heroin
(B) Cocaine
(C) Tobacco
(D) Marijuana



Question. Synthetic drugs structurally related to adrenaline are
(A) Hallucinogens
(B) Analgesics
(C) Amphetamines
(D) Barbiturates



Question. Which one is correctly matched …
(A) Cocaine – Opiate narcotic
(B) Bhang – Analgesic
(C) Reserpine – Tranquilizer
(D) Morphine – Hallucinogen



Question. Which drug is used as medicine to help patients ope with depression and insomnia ?
(A) Morphine
(B) Amphetamines
(C) Codeine



Assertion and Reason Based

Directions : In the following questions a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as :
(A) Both assertion (A) and reason (R) are trueand reason (R) is the correct explanation of assertion (A).
(B) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(C) Assertion (A) is true but reason (R) is false.
(D) Assertion (A) is false but reason (R) is true.

Question. Assertion (A) : Smoking increases the carbon monoxide (CO) content in the blood which has greater affinity to haemoglobin than oxygen.
Reason (R) : CO forms a stable bond with haemoglobin and does not allow binding of oxygen. It reduces concentration of haem bounded oxygen and causes oxygen deficiency in the body.
Answer : (A)

Question. Assertion (A) : Sharing of injection needles between two individuals is not recommended.
Reason (R) : This transmits STDs like AIDS and Hepatitis from the diseased person to the healthy person.
Answer : (A)

Question. Assertion(A) : The colostrum provides passive immunity to the newborn baby.
Reason(R) : In this, the readymade antibodies are directly given to protect the body.
Answer : (A)

Question. Assertion (A) : Heroin, the smack is chemically diacetylmorphine.
Reason (R) : Heroin is obtained by acetylation of morphine.
Answer : (A)

Question. Assertion (A) : Ganja is obtained from Cannabis sativa / hemp plant.
Reason (R) : It is hallucinogenic, alters perception, causes illusion and damages cardiovascular system.
Answer : (A)

Case-based MCQs

Attempt any four sub-parts from each question.
Each sub-part carries 1 mark.
I. Read the following text and answer the following questions on the basis of the same :
Shivani studies in class I. Her parents come from a backward family and are unaware of immunization programme. So, she did not get vaccinated properly.
Once playing with her friends in the park, she fell down due to weakness and later complained of high fever, headache and stiffness in her neck.

Question. A step that can help to eradicate the disease Shivani has contracted is :
(A) Live polio vaccine
(B) Killed polio vaccine
(C) Combination of live and killed vaccines
(D) None of the above



Question. Which vaccine if administered earlier, would have saved Shivani from the illness she contracted unfortunately?
(A) MMR Vaccine
(B) Varicella Vaccine
(C) BCG Vaccine
(D) Salk Vaccine



Question. The disease that Shivani has contracted spreads through :
(A) Mosquito bite
(B) Bite of infected dog
(C) Faecal oral route
(D) Direct contact of an infected person



Question. The microbe responsible for Shivani’s illness may be :
(A) Vibrio cholerae
(B) Enterovirus
(C) Plasmodium
(D) Mycobacterium



Question. This type of infection produces inflammation in :
(A) Bones
(B) Liver
(C) Nervous System
(D) Heart



Very Short Answer Type Questions

Question. Following a road accident four injured persons were brought to a nearby clinic. The doctor immediately injected them with tetanus antitoxin.
(i) What is tetanus antitoxin?
(ii) Why were the injured immediately injected with this antitoxin?
(iii) Name the kind of immunity this injection provided.
Answer : (i) Tetanus antitoxin is a preparation containing antibodies to the toxin. Produced by tetanus bacteria, Clostridium tetani.
(ii) The injured persons are immediately injected with tetanus antitoxin for preventing any infection and septic. Antitoxins neutralise the toxin produced by bacteria.
(iii) Tetanus antitoxin represents artificial passive immunisation where quick response is generated in the body.

Question. Write the scientific name of the source plant of the drugs-marijuana and hashish also mention their effect on human body.
Answer : The scientific names of the source plant of drugs marijuana and hashish is Cannabis sativa. They usually effect the cardiovascular system of human body.

Question. A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions.
Answer : If a person is hypersensitive to certain substance present in the air, he may be allergic to it. Mast cells release certain chemicals, e.g. histamine and serotonin, in response to this substance that results in allergic reaction.
Precaution taken to prevent such reaction is to avoid the allergens responsible for particular allergy.

Question. Name a human disease, its causal organism, symptoms (any three) and vector that spread by intake of water and food contaminated by human faecal matter.
Answer : The disease with given characteristics is amoebiasis. Causative agent is a parasite, Entamoeba histolytica, which is found in the large intestine of human. The transmitting agent of the pathogen is housefly. Symptoms include constipation, abdominal pain, cramps and stools with excess mucus and blood clots.

Question. Lymph nodes are secondary lymphoid organs Explain the role of lymph nodes in our immune response.
Answer : Immune system of human beings consists of lymphoid organs, where the maturation and proliferation of lymphocytes occur. Lymphoid organs are of two types.
These are as follows
(i) Primary lymphoid organs which include bone marrow and thymus where B-and T- lymphocytes mature and acquire their antigen-specific receptor.
(ii) Secondary lymphoid organs which include spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix where lymphocytes interact with the antigen and proliferate to become effector cells.
Lymph nodes are small solid structures present at different points along the lymphatic system. They trap the microorganisms or other antigens that enter the lymph and tissue fluid. Antigens trapped in the lymph nodes activate the lymphocytes and produce an immune response.

Question. How does spleen act as lymphoid organ? Explain.
Answer : Spleen is a large bean-shaped organ containing lymphocytes, phagocytes and large number of erythrocytes. It filters the blood by trapping blood-borne microorganisms. B-cells become activated and produce antibodies in it. Spleen acts as a graveyard of RBCs.

Question. Differentiate between benign tumour and malignant tumour.
Answer : Differences between benign and malignant tumour are as follows (image) 18

Question. Do you consider passive smoking is more dangerous than active smoking? Why?
Answer : Passive smoking can be equally dangerous because it exposes the person to the same harmful effects of smoke. Passive smoking means being in the same room or place, where someone is smoking and getting exposed to smoke in the surrounding area.
Once inhaled, the smoke can trigger mucus release in the bronchioles that blocks the airways. This induces coughing. But prolonged exposure can lead to bronchitis, emphysema, respiratory tract infections and eventually lung cancer.

Question. The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form.
(i) MALT (ii) CMI (iii) AIDS
(iv) NACO (v) HIV
Answer : (i) MALT–Mucosal Associated Lymphoid Tissue
(ii) CMI–Cell-Mediated Immunity
(iii) AIDS–Acquired Immuno Deficiency Syndrome
(iv) NACO–National AIDS Control Organisation
(v) HIV–Human Immunodeficiency Virus

Question. Why cannabinoids are banned in sports and games?
Intake of cannabinoids should be banned. Justify giving reasons.
Answer : Cannabinoids are banned in sports as athletes were misusing these drugs in order to enhance their performance. These can have a serious negative effect on their general health and in long term, can hamper the normal functioning of organ systems. Hence, intake of cannabinoids should be banned.

Question. The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen.
(i) Name the disease, the patient is suffering from.
(ii) What is the causative organism?
(iii) Which cells of body are affected by the pathogen?
Answer : (i) The patient is suffering from AIDS.
(ii) AIDS is caused by Human Immunodeficiency Virus (HIV). It is a retrovirus containing RNA as genetic material.
(iii) Macrophages and helper T-cells are affected by the pathogen.

Question. In the metropolitan cities of India, many children are suffering from allergy/asthma. What are the main causes of this problem? Give some symptoms of allergic reactions.
Answer : In metropolitan cities, lifestyle is responsible for lowering of immunity and high sensitivity to allergens. The polluted environment of cities, which affect the respiratory system is the reason of allergy/asthma in childrens.
Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing.

Question. (i) What precaution(s) would you recommend to a patient requiring repeated blood transfusion?
(ii) If the advise is not followed by the patient, there is an apprehension that the patient might contract a disease that would destroy the immune system of his/her body. Explain with the help of schematic diagram only how the immune system would get affected and destroyed.
Answer : (i) Repeated blood transfusion may result in contracting diseases like AIDS. The recipient must ensure that the donor’s blood is being screened for HIV and other pathogens.
(ii) In the absence of such measures, the patient can get infected by HIV (Human Immmunodeficiency Virus) which causes AIDS. It is a threatening disorder that weakens the immune system by attacking helper T-cells in the body.
(image) 17

Question. 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 : It is difficult to get rid of alcohol or drugs once a person starts taking them because their repeated use lead to addiction. It increases the tolerance level of these substances in the body and then the receptors respond only to higher doses of alcohol and drugs which in turn increases the dosage and it becomes difficult to get rid of the habit.

Question. What is cancer? How is a cancer cell different from the normal cell? How do normal cells attain cancerous nature?
Answer : An abnormal and uncontrolled division of cells is termed as cancer. Genes called cellular oncogenes (c-onc) or proto-oncogens present in normal cells when activated under certain conditions lead oncogenic transformation of the normal cells leading cancer.
A cancer cell is different from the normal cell in following ways
(image) 18

Question. Due to under peer pressure, a group of adolescents started using opioids intravenously. What are the serious problems they might face in future?
Answer : Serious problems, they might face in future are
(a) Higher risk of infections likes AIDS and hepatitis-B which transmits through sharing of infected needle and syringes or sexual contact.
(b) Since, the tolerance levels of the receptors present in our body to these drugs elevates, they respond only to higher doses of drugs leading to greater intake and addiction.

Question. Give the full form of CT and MRI. How are they different from each other? Where are they used?
Answer : CT is Computed Tomography which uses X-rays to generate 3D images of internal organs MRI is Magnetic Resonance Imaging which uses strong magnetic fields and non-ionising radiations to detect pathological and physiological changes in the living tissue accurately. Both are used in cancer detection.

Question. How are morphine and heroin related? Mention the effect each one of them has on the human body?
Answer : Heroin is obtained from acetylation of morphine. They both affect the central nervous system and gastrointestine tract. Thus, both are related. Morphine, is as an effective sedative and painkiller while heroin acts as depressant and slows down body functions.

Question. Name the body system affected by cannabinoids.
Answer : Cannabinoids affect the cardiovascular system of the body.

Question. When Rheumatoid arthritis is caused ?
Answer : Rheumatoid arthritis is caused when the body attack self cells and the ability to differentiate pathogens or foreign molecules from self cells is lost. 

Question. Breast fed babies are more immune to diseases than the bottle fed babies. Why?
Answer : The mother’s milk consists of antibodies (Ig A) such antibodies are not available to bottle fed babies

Question. Name the pathogen which causes malignant malaria.
Answer : Plasmodium falciparum

Question. You have heard of many incidences of Chickungunya in our country. Name the vector of the disease.
Answer : Aedes mosquitoes

Question. Fill the blanks 1,2,3,4,5,6 in the given table.

Answer : i) Alveoli filled with fluid, reduced breathing, fever, chills, cough and headache.
(ii) Salmonella typhi
(iii) Common Cold
(iv) Internal bleeding, muscular pain, anaemia, fever and blockage of the intestinal passage.
(v) Microsporum species/Trichophyton species/Epidermophyton Species.
(vi) Amoebiasis/amoebic dysentery.

Question. Which micro organism is used to produce hepatitis B Vaccine?
Answer : Yeast

Question. What is the reason of shivering in malarial patient?
Answer : After sporozoite infection, when RBC ruptures, a toxic substance haemozoin is released which cause chilling and high fever.

Question. Where are B-cells and T-cells formed? How do they differ from each other?
Answer : B-cells and T-cells are formed in bone marrow. B-cells produce antibodies but T cells do not produce antibodies but help B-cells to produce them

Question. Given below are the pathogens and the diseases caused by them. Which out of these pairs is not correct matching pair and why?
(a) Wuchereria .Filariasis
(b) Microsporum .Ringworm
(c) Salmonella . Common Cold
(d) Plasmodium .Malaria
Answer : – Salmonella :Common cold is not a matching pair.

Question. What would happen to the immune system, if thymus gland is removed from the body of a person?
Answer :  T-lymphocytes develop and mature in thymus gland, Immune system will become weak on removal of thymus gland

Question. Lymph nodes are secondary lymphoid organs. Describe the role of lymph nodes in our immune response.
Answer : Lymph nodes provide the sites for interaction of lymphocytes with the antigen.
When the microorganisms enter the lymph nodes, lymphocytes present there are activated and cause the immune response.

Question. A person shows unwelcome immunogenic reactions while exposed to certain substances.
(a) Name this condition.
(b) What common term is given to the substances responsible for this condition?
(c) Name the cells and the chemical substances released which cause such reactions.
Answer : (a) Allergy (b) Allergens (c) Mast Cells. Histamine, Serotonin

Question. What Is the role of histamine in inflammatory response? Name few drugs which reduce the symptoms of allergy.
Answer : Histamine acts as allergy-mediator which cause blood vessels to dilate.
It is released by mast cells. Antihistamine steroids and adrenaline quickly reduce the symptoms of allergy.

Question. Name the diagnostic test which confirms typhoid.
Answer : Widal test

Question. Name the two major groups of cells required to attain specific immunity.
Answer : B-lymphocytes and T-lymphocytes

Question. What are Cannabinoids? From which plant Cannabinoids are obtained? Which part of the body is affected by consuming these substances?
Answer : Cannabinoids are a group of chemicals which interact with Cannabinoid receptors present principally in the brain. Cannabinoids are obtained from the inflorescences of the plant Cannabis sativa. 
The substances affect the cardiovascular system adversely

Question. How do cytokine barriers provide innate immunity in humans?
How do cytokine barriers help in evading viral infections ?
Answer : Interferon (proteins), secreted by virus-infected cells protect non-infected cells from further viral infection.

Question. Name three important disorders caused by alcohol.
Answer : Pancreatitis, alcoholic hepatitis and liver cirrhosis.

Question. How do monocytes act as a cellular barrier in humans to provide innate immunity ?
In what way is monocyte a cellular barrier with reference to immunity ?
Answer : Phagocytosis of microbes / destroy microbes.

Question. Name the immune response which is responsible for the rejection of tissues/organs in the patients body part transplantation.
Answer : The cell-mediated immune response is responsible for the rejection of tissues/organs in the body part transplantation. The body is capable to differentiate self and non self cells. 

Question. Name the condition in vertebrates where the body attacks self-cells.
Answer : Autoimmune disorder or autoimmune disease.

Question. Name the stage of Plasmodium that gains entry into the human when bitten by an infected  female Anopheles Mosquito.
Answer : Sporozoites

Question. A patient is down with Amoebiasis. List the symptoms that confirm this infection. Name the causative pathogen.
Answer : Constipation, abdominal pain, stools with mucous, blood clot. Causative pathogen 

Short Answer Type Questions

Question. How is the normal human body temperature of 37°C maintained during (i) Summer, and (ii) Winter? Explain. 
Answer : Human beings maintain a constant temperature of 37°C. In summers, the outside temperature is much higher than our body temperature. Therefore, we sweat profusely. This results in evaporative cooling, and our body temperature is reduced to normal. In winters, the outside temperature is much lower than our body temperature. Therefore, we shiver,which is a kind of exercise, which produces heat  and raises the body temperature. 

Question. Mention any three causes of drug abuse. Suggest some measures for the prevention and control of drug abuse.
Answer : Reasons to attract towards drug abuse: Curiosity, peer pressure, escape from
frustration and failure, family problems, false belief of enhanced performance. Preventive measures:
Avoid undue peer pressure
Education and Counseling
Seeking help from parents and peers.
Looking for danger signs
Seeking professional and medical help

Question. The pathogen of a disease depends on RBCs of human for growth and reproduction. The person with this pathogen suffers with chill and high fever.
(a) Identify the disease.
(b) Name the pathogen.
(c) What is the cause of fever?
(d) Represent the life cycle of the pathogen diagrammatically.
Answer : (a) Malaria(b) Different species of Plasmodium viz P. vivax, P. Malariae and P.falciparum.(c) Malaria is caused by the toxins (haemozoin) produced in the human body by the malarial parasite. This toxin is released by the rupturing of RBCs. (d) Life cycle of Plasmodium

Question. What is innate immunity? List the four types of barriers which protect the body from the entry of the foreign agents.
Answer : Innate Immunity is non-specific type of defense that is present at the time of birth.
(i) Physical Barriers: Skin, mucous-coated epithelium or respiratory, digestive and urino genital tract.
(ii) Physiological Barriers: Acidity of Stomach, lysozyme in saliva, tears, sweat.
(iii) Cellular Barrier: Macrophages, neutrophils, monocytes and natural killer lymphocytes.(iv)Cytokine Barriers: Interferons produced by Viral infected cells, protect the non-infected cells from further Viral infection

Question. Municipal corporation has deputed personnel to check for mosquito in your school.
i) Which are the places they should check for mosquitoes & their larvae?
ii) Name two diseases which are spread by mosquitoes and their larvae?
Answer : I) Places like water tanks, flower pots, stagnant water.
ii)Dengue, malaria, filariasis, chikungunya

Question. Answer the following with respect to Cancer.
(a) How does a cancerous cell differ from a normal cell
(b) Benign tumour is less dangerous than malignant tumour. Why?
(c) Describe causes of cancer.
(d) Mention two methods of treatment of the disease.
Answer : 
(a) In normal cells, growth and differentiation is highly controlled and regulated (contact inhibition). The cancerous cells have lost the property of contact inhibition, hence continue to divide giving rise to masses of cells(tumors).
(b) The benign tumor remains confined in the organ affected as it is enclosed in a connective tissue sheath and does not enter the metastatic stage.(c)Cancer may be caused due to carcinogens which are physical(radiations),chemicals (Nicotine, Aflatoxin, Cadmium oxide, Asbestos) and biological (viral oncogens)(d) Surgery, radiotherapy, Chemotherapy

Question. 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.
(b) Which pathogen is identified by ELISA test?
(c) Which cells of the body are attacked by the pathogen?
(d) Suggest preventive measure of the infection.
Answer : (i) AIDS (Acquired Immuno Deficiency Syndrome)
(ii) HIV (Human Immunodeficiency Virus)
(iii) Helper T-cells, macrophages, B-lymphocytes.
(iv) Preventive measures:
(a) People should be educated about AIDS transmission.
(b) Disposable needles and syringes should be used
(c) Sexual habits should be changed immediately
(d) High-risk groups should be discouraged from donating blood.
(e) Routine screening may be done

Question. Prior to a sports events, blood and urine samples of sportspersons are collected for drug tests.
(i) Why is there a need to conduct such tests ?
(ii) Name the drugs the authorities usually look for.
(iii) Write the generic names of two plants from which these drugs are obtained.
Answer : (i) To detect drug abuse / use of banned drugs / use of cannabinoids / anabolic steroids / narcotic analgesic diuretics / hormones / drugs used to accelerate performance / increase muscle strength / bulk / promote aggressiveness / to ensure fair game.
(ii) Cannabinoids / cocaine / coca alkaloid / coke / crack / hashish / charas / ganja / hemp plant extract.
(iii) Cannabis / Atropa / Erythroxylum / Datura.

Question. Why is the structure of an antibody molecule represented as H2L2? Name any two types of antibodies produced in a human body.
Answer : L2 = Two light / small polypeptide chains, H2= two heavy / longer polypeptide chains.

Question. Differentiate between opioids and cannabinoids on the basis of their
(a) specific receptor site in human body.
(b) mode of action in human body.
Answer : Differences between opioids and cannabinoids : 

Specific receptor site in human body.Receptors of opioids
are located in the GI tract
and central nervous system.
Receptors are located in the brain only.
Mode of action in human body.Act as depressant and slows down the body functions.Affects the cardiovascular system of the body.

Question. Mention one application for each of the following :
(a) Passive immunization
(b) Anti-histamine
(c) Colostrum
(d) Cytokine-barriers
Answer : (a) Provide preformed antibodies / anti-toxins for quick response in case of infection by deadly microbes (tetanus) or snake bite.
(b) Reduces symptoms of allergy.
(c) Provides passive immunity / antibodies / Ig A from mother to a new born.
(d) Protection of non-infected cells from further viral infection.

Question. (a) What precautions would you recommend to a patient requiring repeated blood transfusion?
(b) If the advice is not followed by the patient, there is an apprehension that the patient might contract a disease that would destroy the immune system of his/her body. Explain with the help of schematic diagram only how the immune system would get affected and destroyed.
Answer : (a) Ensuring blood (from blood banks) is safe from HIV / screening blood for HIV / AIDS/Hepatitis / ensuring use of only disposable needles and syringes in (public and private)
hospitals / clinic. 

Question. Name the type of immunity that the colostrum provides to a newborn baby. Write by giving an example where this type of immunity should be provided to a person.
Answer : Passive Immunity.

Question. Differentiate between the roles of B-lymphocytes and T-lymphocytes in generating immune responses.
Principle of vaccination is based on the p operty of “memory” of the immune system. Taking one suitable example, justify the statement.
Answer : B-lymphocytes : Produce antibodies 1 T-lymphocytes : Help B-lymphocytes to produce antibodies / kills the pathogen directly (Killer T-cells). 
When a vaccine / heat killed pathogen / attenuated pathogen / weakened pathogen / a preparation of antigenic proteins of pathogen is introduced into the body to prevent chicken pox / measles / any other example. It produces antibodies against antigen /pathogen.  It generates B and T memory cells that recognize the pathogen quickly on subsequent exposure , to
produce large amount of antibodies that inactivate the pathogen causing the disease.

Question. (a) Name the source plant of heroin drug. How is it obtained from the plant?
(b) Write the effects of heroin on the human body.
Answer : (a) Papaver somniferum / Poppy plant.
Extracted from latex of the plant / acetylation of morphine (obtained from the latex of plant).
(b) Depressant, slows down body function.

Question. Show with the help of a flow chart only, the life cycle of malarial parasite in humAnswer :
Name the form of Plasmodium that gains entry into the human body. Explain the different stages of its life-cycle in the human body. 
Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles. 
Name the stage of Plasmodium that is transmitted to human body by the vector. Describe the life cycle of the parasite in humAnswer :

Answer : When mosquito bites, sporozoites are injected into bloodstream → parasite reaches the liver cells and multiplies → liver cells burst releasing parasite into the blood → parasites then enter into RBCs multiplying and bursting them → male gametocytes, female gametocytes develop in RBCs 

Question. What is a vaccine ? How does it act to provide long term immunity to an individual who is vaccinated ?
Answer : A vaccine is an antigen protein of pathogens or inactivated or weakened pathogens or their toxin.
When it is introduced into the body of a person who is required to be made immune, it stimulates the production of antibodies and memory cells which is called primary response. It produces memory cells when this pathogen enters the second time. These memory cells show rapid and massive responses so that body become immune to this pathogen. 

Question. During a school trip to ‘Rohtang Pass’, one of your classmates suddenly developed ‘altitude sickness’. But, she recovered after some time.
(a) Mention one symptom to diagnose the sickness.
(b) What caused the sickness?
(c) How could she recover by herself after some time?
Answer : (a) Nausea / fatigue / heart palpitation. 
(b) Low atmospheric pressure at high altitude, body deprived of O2. 
(c) Increase in RBC, decreases binding capacity of haemoglobin, increased breathing rate, get acclimatised.

Question. Name and state the effect of a drug that is often medically prescribed, but its overuse leads to drug dependence and drug abuse.
Answer : Morphine, barbiturate, amphetamines, benzodiazepines, lysergic acid diethyl amides (LSD).

Question. Name the cells, HIV (Human Immunodeficiency Virus) gains entry into after infecting
the human body. Explain the events that occur in these cells.
Answer : HIV (Human immune deficiency virus) enters into macrophages after getting into the human body. HIV multiplies first in macrophages and then in helper T-cells or lymphocytes.
Events that occur in the human host after the entry of HIV :
(i) After entering the human body, the HIV virus attacks and enters the macrophages.
(ii) Inside the macrophages, the RNA of the virus replicates with the help of enzyme reverse transcriptase and give rise to viral DNA.
(iii) Then, this viral DNA incorporates into the host cell DNA, uses raw materials and infected cell machinery and directs the synthesis of virus particles.
(iv) At the same time, HIV enters the helper T-lymphocytes, replicates and produce progenies.
(v) As a result, T-lymphocytes start decreasing in number and immune response of the person becomes weak

Question. Study the diagram showing the entry of HIV into the human body and the processes that are followed : 

(a) Name the human cell ‘A’ HIV enters into.
(b) Mention the genetic material ‘B’ HIV releases into the cell.
(c) Identify enzyme ‘C’. AE
Answer : (a) A is helper T-cells
(b) B is RNA
(c) C is Reverse transcriptase 

Question. (i) Which organ of the human body is initially affected when bitten by an infected female Anopheles? Name the stage of the parasite that infects this organ.
(ii) Explain the events that are responsible for chill and high fever in the patient.
Answer : (i) Liver cells, sporozoites.
(ii) Parasites reproduce asexually in RBC / multiply, Rupture of RBCs is associated with release of toxic substance called as hemozoin.

Question. Explain the following with reference to drug/alcohol abuse : (i) Addiction, (ii) dependence and (iii) withdrawal symptoms.
Answer : (i) Addiction : Frequent use of drugs or alcohol leads to increase in the level of tolerance of receptors present in our body, thus making these receptors respond to only higher doses of drugs and alcohol.
Psychological attachment to certain effects such as euphoria and temporary feeling of well being associated with drugs and alcohol.
(ii) Dependence : Due to inherent addictive nature and its psychological attachment to drugs or alcohol and are unable to live without them. 
(iii) Refer Q. 17. SATQ-I.

Question. What happens to an individual when a regular dose of drugs/alcohol is abruptly discontinued? What characteristics manifest in the individual under such a situation ?
What is “withdrawal syndrome” ? List any two symptoms, it is characterized by.
Answer : Withdrawal syndrome. 
Manifestation of unpleasant characteristics and feelings.
Anxiety, shakiness, nausea and sweating.

Question. How are oncogenic viruses different from proto-oncogenes?
Answer : Oncogenic viruses are cancer causing viruses /external cancer causing factor.
Proto-oncogenes : Identified in normal cells which when activated (under certain conditions) could lead to oncogenic transformation of cells / internal cancer causing factor.

Long Answer Type Questions

Question. (a) If a patient is advised anti-retroviral drug, name the possible infection he/ she is likely to be suffering from. Name the causative organism.
(b) How do vaccines prevent subsequent microbial infection by the same pathogen?
(c) How does a cancerous cell differ from a normal cell?
(d) Many microbial pathogens enter the gut of humans along with food. Name the physiological barrier that protects the body from such pathogens.

Answer : (a) AIDS is caused by the HIV (Human Immuno-Deficiency Virus). 
(b) Vaccines prevent microbial infections by initiating production of antibodies against these antigens to neutralise the pathogenic agents during later actual infection. 
The vaccines also generate memory – B and T-cells that recognize the pathogen quickly onsu bsequent exposure. 
(c) Normal cells show a property called “contact inhibition” by virtue of which contact with other cells inhibits their uncontrolled growth.
Cancer cells appear to have lost this property.
These cells grow very rapidly, invading and damaging the surrounding normal tissues.
Cells sloughed from such tumours reach distant sites through blood, and wherever they get lodged in the body, they start a new tumour there. This property is called metastasis.

Question. (a) Differentiate between active and passive immunity.
(b) Comment on the role of vaccination and immunization in keeping human population healthy.
Answer : (a)

Active immunityPassive immunity
The immunity produced by the antibodies of the host in response to a direct contact of an antigenThe immunity produced when ready-made antibodies are directly given from outside to the host.
Slow and takes time to give its full effective
Immunity develops immediately and hence there is no time lag.
It generates an immunological memory.Doesn’t generate immunological memory.

(b) Role of vaccination / immunization :
– Antibodies produced in body against antigen neutralizes pathogenic agents.
– Vaccines also generate memory cell ( B and T cells) that recognize quickly on subsequent exposure and controls growth of pathogen with massive production of antibodies.
– Preformed antibodies/ antitoxin protect our body from deadly microbes like tetanus and against snake venom.

Question. (i) Name the type of lymphoid organslymph nodes and thymus are. Explain the role played by them in causing immune response.
(ii) Differentiate between innate immunity and acquired immunity.
Answer : (i) 

Innate ImmunityAcquired Immunity
Non-specific type of response.Pathogen-specific defence.
Present at the time of birth.Acquired by the body after birth.
Provides a barrier to the entry of foreign agents
into our body.
Characterised by memory.

Human Health and Diseases Class 12 Biology Important Questions

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