CBSE Class 12 Biology Human Health And Diseases Worksheet

Important Questions for NCERT Class 12 Biology Human Health and Diseases

Question. The infectious stage of Plasmodium that enters the human body is
(a) Trophozoites
(b) Sporozoites
(c) Female gametocytes
(d) Male gametocytes

Answer: B

Question. Match the following diseases with the causative organism and select the correct option.
  Column-I                     Column-II
A. Typhoid               (i) Wuchereria
B. Pneumonia         (ii) Plasmodium
C. Filariasis             (iii) Salmonella
D. Malaria               (iv) Haemophilus
      A    B   C   D
(a) (i) (iii) (ii) (iv)
(b) (iii) (iv) (i) (ii)
(c) (ii) (i) (iii) (iv)
(d) (iv) (i) (ii) (iii) 

Answer: B

Question. Identify the correct pair representing the causative agent of typhoid fever and the confirmatory test for typhoid.
(a) Salmonella typhi / Widal test
(b) Plasmodium vivax / UTI test
(c) Streptococcus pneumoniae / Widal test
(d) Salmonella typhi / Anthrone test

Answer: A

Question. In which disease does mosquito transmitted pathogen cause chronic inflammation of lymphatic vessels?
(a) Elephantiasis
(b) Ascariasis
(c) Ringworm disease
(d) Amoebiasis

Answer: A

Question. Which of the following sets of diseases is caused by bacteria?
(a) Cholera and tetanus
(b) Typhoid and smallpox
(c) Tetanus and mumps
(d) Herpes and influenza 

Answer: A

Question. Which of the following diseases is caused by a protozoan?
(a) Babesiosis
(b) Blastomycosis
(c) Syphilis
(d) Influenza 

Answer: A

Question. Match each disease with its correct type of vaccine.
       Column I                 Column II
A. Tuberculosis           (i) Harmless virus
B. Whooping cough    (ii) Inactivated toxin
C. Diphtheria               (iii) Killed bacteria
D. Polio                       (iv) Harmless bacteria
(a) A-(iv), B-(iii), C-(ii), D-(i)
(b) A-(i), B-(ii), C-(iv), D-(iii)
(c) A-(ii), B-(i), C-(iii), D-(iv)
(d) A-(iii), B-(ii), C-(iv), D-(i) 

Answer: A

Question. The active form of Entamoeba histolytica feeds upon
(a) food in intestine
(b) blood only
(c) erythrocytes, mucosa and submucosa of colon
(d) mucosa and submucosa of colon only.

Answer: C

Question. Infection of Ascaris usually occurs by
(a) Tse-tse fly
(b) mosquito bite
(c) drinking water containing eggs of Ascaris
(d) eating imperfectly cooked pork.

Answer: C

Question. Identify the site where Wuchereria bancrofti is normally found in human body.
(a) Muscles of the legs
(b) Blood vessels of the thigh region
(c) Skin between the fingers
(d) Lymphatic vessels of the lower limbs

Answer: D

Question. Motile zygote of Plasmodium occurs in
(a) gut of female Anopheles
(b) salivary glands of Anopheles
(c) human RBCs
(d) human liver. 

Answer: A

Question. Widal test is carried out to test
(a) malaria
(b) diabetes mellitus
(c) HIV/AIDS
(d) typhoid fever. 

Answer: D

Question. Common cold differs from pneumonia in that
(a) pneumonia is a communicable disease whereas the common cold is a nutritional deficiency disease
(b) pneumonia can be prevented by a live attenuated bacterial vaccine whereas the common cold has no effective vaccine
(c) pneumonia is caused by a virus while the common cold is caused by the bacterium Haemophilus influenzae
(d) pneumonia pathogen infects alveoli whereas the common cold affects nose and respiratory passage but not the lungs. 

Answer: D

Question. Where will you look for the sporozoites of the malarial parasite?
(a) Saliva of infected female Anopheles mosquito
(b) Red blood corpuscles of human suffering from malaria
(c) Spleen of infected humans
(d) Salivary glands of freshy moulted female Anopheles mosquito 

Answer: A

Question. Which one of the following options gives the correct match of a disease with its causative organism and mode of infection?
  Disease                      Causative                          Mode of infection
(a) Typhoid              Salmonella typhi                     With inspiredair
(b) Pneumonia        Streptococcus pneumoniae    Droplet infection
(c) Elephantiasis      Wuchereria bancrofti             With infected water and food
(d) Malaria                 Plasmodium vivax               Bite of male Anopheles mosquito

Answer: B

Question. Common cold is not cured by antibiotics because it is
(a) caused by a virus
(b) caused by a Gram-positive bacterium
(c) caused by a Gram-negative bacterium
(d) not an infectious disease. 

Answer: A

Question. Ringworm in humans is caused by
(a) bacteria
(b) fungi
(c) nematodes
(d) viruses. 

Answer: B

Question. Widal test is used for the diagnosis of
(a) malaria
(b) pneumonia
(c) tuberculosis
(d) typhoid. 

Answer: D

Question. A person suffering from a disease caused by Plasmodium, experiences recurring chill and fever at the time when
(a) the sporozoites released from RBCs are being rapidly killed and broken down inside spleen
(b) the trophozoites reach maximum growth and give out certain toxins
(c) the parasite after its rapid multiplication inside RBCs ruptures them, releasing the stage to enter fresh RBCs
(d) the microgametocytes and megagametocytes are being destroyed by the WBCs.

Answer: C

Question. Which of the following is a pair of viral diseases?
(a) Common cold, AIDS
(b) Dysentery, common cold
(c) Typhoid, tuberculosis
(d) Ringworm, AIDS

Answer: A

Question. Match the disease in column I with the appropriate items (pathogen / prevention / treatment) in column II.
     Column I                Column II
A. Amoebiasis         (i) Treponema pallidum
B. Diphtheria          (ii) Use only sterilised food and water
C. Cholera              (iii) DPT vaccine
D. Syphilis              (iv) Use oral rehydration therapy
(a) A – (ii), B – (i), C – (iii), D – (iv)
(b) A – (ii), B – (iii), C – (iv), D – (i)
(c) A – (i), B – (ii), C – (iii), D – (iv)
(d) A – (ii), B – (iv), C – (i), D – (iii) 

Answer: B

Question. HIV that causes AIDS, first starts destroying
(a) helper T-lymphocytes
(b) B-lymphocytes
(c) leucocytes
(d) thrombocytes
Answer : A

Question. The sporozoites that cause infection when a female Anopheles mosquito bites a person, are formed in 
(a) liver of the person
(b) RBCs of mosquito
(c) salivary glands of mosquito
(d) gut of mosquito
Answer : D

Question. Dengue in humans is caused by
(a) Viruses
(b) Bacteria
(c) Fungi
(d) Helminthes
Answer : A

Question. The disease chikungunya is transmitted by 
(a) house fly
(b) Aedes mosquito
(c) cockroach
(d) female Anopheles
Answer : B

Question. Many diseases can be diagnosed by observing the symptoms in the patient. Which group of symptoms are indicative of pneumonia? 
(a) Difficulty in respiration, fever, chills, cough, headache
(b) Constipation, abdominal pain, cramps, blood clots
(c) Nasal congestion and discharge, cough, constipation, headache
(d) High fever, weakness, stomach pain, loss of appetite and constipation
Answer : A

Question. In malignant tumors, the cells proliferate, grow rapidly and move to other parts of the body to form new tumors. This stage of disease is called 
(a) metagenesis
(b) metastasis
(c) teratogenesis
(d) mitosis
Answer : B

Question. When an apparently healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that 
(a) the patient was not efficient at his work
(b) the patient was not economically prosperous
(c) the patient shows behavioural and social maladjustment
(d) he does not take interest in sports
Answer : C

Question. Which of the following are the reason(s) for rheumatoid arthritis? Choose the correct option.
(i) The ability to differentiate pathogens or foreign molecules from self cells increases.
(ii) Body attacks self cells
(iii) More antibodies are produced in the body
(iv) The ability to differentiate pathogens or foreign molecules from self cells is lost
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (iii) and (iv)
(d) (i) and (iii)
Answer : B

Question. B-lymphocytes are associated with
(a) Humoral immunity
(b) Inflammatory response
(c) Cell mediated immunity
(d) Phagocytosis
Answer : A

Question. The substance produced by a cell in viral infection that can protect other cells from further infection is
(a) serotonin
(b) colostrum
(c) interferon
(d) histamine
Answer : C

Question. Transplantation of tissues/organs to save certain patients often fails due to rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?
(a) Auto-immune response
(b) Humoral immune response
(c) Physiological immune response
(d) Cell-mediated immune response
Answer : D

Question. Which of the following is not the causal organism for ringworm? 
(a) Microsporum
(b) Trichophyton
(c) Epidermophyton
(d) Macrosporum
Answer : D

Question. LSD is obtained from
(a) Erythroxylum coca
(b) Cannabis sativa
(c) Claviceps purpurea
(d) Papaver somniferum
Answer : C

Very Short Answer Questions 

Question. Millions of chickens were killed in West Bengal, Orissa and Maharashtra recently. What was
the reason?
Answer. Millions of chickens were killed (culled) in West Bengal, Orissa and Maharashtra because they were found to be infected with H5N1 virus, the causal organism of Bird Flu.

Question. Why do pollen grains of some flowers trigger ‘sneezing’ in some people? 
Answer. Pollen grains trigger sneezing by causing allergic reaction.

Question. How do interferons protect us? 
Answer. Interferons protect non-infected cells from further viral infections, by creating cytokine barriers.

Question. When does a human body elicit an anamnestic response?
Answer. At the time of secondary response.

Question. State the functions of mast cells in allergy response.
Answer. Mast cells release chemicals like histamine and serotonin in allergic response.

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 two diseases whose spread can be controlled by the eradication of Aedes mosquitoes.
Answer. Dengue, Chikungunya//Yellow Fever / Eastern Equine Encephalitis / West Nile Fever / Zika / Zika Viral Disease.

Question. Name the category of disease in which ‘Rheumatoid arthritis‘ in human is put under.
Answer. Autoimmune disease.

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

Question. What is the function of Opioids ?
Answer. Opioids act as pain killers.

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

Question. The principle of vaccination is based on which property?
Answer. The principle of vaccination is based on the property of memory. 

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

Question. What is an autoimmune disease? Give an example. 
Answer. It is an abnormal immune response in which the immune system of the body starts rejecting its own body cells or ‘self’ cells and molecules. For example, rheumatoid arthritis.

Question. Name two STDs which can be transmitted through contaminated blood.
Answer. Hepatitis-B and AIDS are the two STDs which can be transmitted through contaminated blood.

Question. Name the category of the disease: Rheumatoid arthritis. 
Answer. Auto-immune disease.

Short Answer Questions

Question. A student on a school trip started sneezing and wheezing soon after reaching the hill station for no explained reasons. But, on return to the plains, the symptoms disappeared. What is such a response called? How does the body produce it? 
Answer. Such a response is called allergic reaction or allergy. On exposure to allergens like dust, pollens,etc., chemicals like histamine and serotonin are released from the mast cells, resulting in an allergic response.

Question. A young boy when brought a pet dog home started to complain of watery eyes and running nose. The symptoms disappeared when the boy was kept away from the pet.
(a) Name the type of antibody and the chemicals responsible for such a response in the boy.
(b) Mention the name of any one drug that could be given to the boy for immediate relief from such a response. 
Answer. (a) Antibody: IgE; chemicals: Histamine and serotonin
(b) Drugs: Antihistamine, adrenalin, steroids. (Any one)

Question. Name and explain the two types of immune responses in humans. 
Answer. The two types of immunity are active immunity and passive immunity.
Active immunity: Immunity developed in the host body due to production of antibodies in response to antigens.
Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents.
OR
The two types of immunity are humoral immunity and cell-mediated immunity.
Humoral immunity: Immune responses given by antibodies found in the blood.
Cell-mediated immunity: Activation of T-lymphocytes mediate this immunity.
OR
The two types of immunity are primary immunity and secondary immunity.
Primary immunity: When our body encounters a pathogen for the first time, it produces primary response.
Secondary immunity: Subsequent encounter with the same pathogen generates highly intensified secondary response or secondary immunity.

Question. Describe the role of lymph nodes in providing immunity. 
Answer. Lymph nodes trap microorganisms or other antigens. These trapped antigens activate lymphocytes present in the lymph and cause an immune response.

Question. State the functions of primary and secondary lymphoid organs in humans. 
Answer. Primary lymphoid organs are the sites where immature lymphocytes differentiate into antigen sensitive lymphocytes.
Secondary lymphoid organs are the sites where the lymphocytes interact with antigens and proliferate to become effector cells.

Question. (a) Name one primary and one secondary lymphoid organ in the human body.
(b) How do they differ in their functions? 
Answer. (a) Primary lymphoid organ: Bone marrow/thymus. (Any one)
Secondary lymphoid organ: Spleen/Lymph nodes/Mucosal associated lymphoid tissue (MALT). (Any one)
(b) Primary lymphoid organs are the sites where immature lymphocytes differentiate into antigen sensitive lymphocytes.
Secondary lymphoid organs are the sites where the lymphocytes interact with antigens and proliferate to become effector cells.

Question. (a) Name the lymphoid organ in humans where all the blood cells are produced.
(b) Where do the lymphocytes produced by the lymphoid organ mentioned above migrate and how do they affect immunity?
Answer. (a) Bone marrow.
(b) The lymphocytes produced migrate to secondary lymphoid organs like spleen, lymph nodes,etc. They trap the microorganisms thereby activating the lymphocytes present in the lymph nodes and produce an immune response.

Question. (a) Highlight the role of thymus as a lymphoid organ.
(b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity.
Answer. (a) Immature lymphocytes differentiate into mature T-lymphocytes and become antigensensitive in thymus.
(b) T-lymphocytes are released from thymus. T-cells help B-cells to produce antibodies and provide cell-mediated immunity.

Question. How does spleen act as a lymphoid organ? Explain.
Answer. The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne microorganisms. Spleen also has a large reservoir of erythrocytes.

Question. Identify A, D, E and F in the diagram of an antibody molecule given below:

Answer. A—Antigen binding site D—Light chain
E—Heavy chain F—Disulfide bridge.

Question. Why is tobacco smoking associated with rise in blood pressure and emphysema (oxygen deficiency in the body)? Explain.
Answer. Tobacco has nicotine that stimulates the release of adrenaline and noradrenaline which raise blood pressure. Smoking tobacco releases carbon monoxide which reduces the concentration of haem-bound oxygen. This causes emphysema.

Question. When you go for a trek/trip to any high altitude places, you are advised to take it easy and rest for the first two days. Comment, giving reasons. 
OR
Why do tribes who live in high altitude of Himalayas experience discomfort in respiration?
How do they get adapted to survive in such a situation? 
Answer. At high altitudes it is advised to take easy due to low oxygen availability. This may also cause altitude sickness. It is also advised to take rest because body compensates the low oxygen availability during rest by increasing RBC production and decreasing the binding capacity of haemoglobin, in turn increasing the breathing rate.

Question. What would happen to immune system, if thymus gland is removed from the body of a person? 
Answer. Thymus is the primary lymphoid organ. In thymus gland, immature lymphocytes differentiate into antigen-sensitive lymphocytes. If thymus gland is removed from the body of a person,his immune system becomes weak. As a result the person’s body becomes prone to infectious diseases.

Question. Why an immunosuppressive agent is taken after an organ transplant? 
Answer. Our immune system is capable to differentiate between ‘self’ and ‘non-self’ cells/tissues. The graft (grafting) is a non-self tissue which may be rejected by our immune system. So, to prevent the rejection, immunosuppressants are taken after the transplant.

Question. How are auto-immune diseases different from immunodeficiency disease? Give one example of each in human.
Answer. Differences between auto-immune and immunodeficiency diseases

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. Allergy is the exaggerated response of the immune system to certain antigens present in the environment. In metropolitan cities lifestyle is responsible in lowering of immunity and sensitivity to allergens. More polluted environment increases the chances of allergy in children.Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing.

Question. Identify A, B, C and D in the replication of HIV (retrovirus).

Answer. (A) Reverse transcription.
(B) Viral DNA incorporates into host genome.
(C) New viral RNA produced by infected cell.
(D) New viruses can infect other cells.

Question. Name the cells that act as HIV factory in humans when infected by HIV. Explain the events that occur in the infected cell. 
OR
Name the type of cells the AIDS virus first enters into after getting inside the human body.
Explain the sequence of events that the virus undergoes within these cells to increase their progeny.
Answer. Macrophages/Helper T-cells act as HIV factory.
The virus enters macrophages or helper T-cells where RNA genome of the virus forms viral DNA with the help of the enzyme reverse transcriptase. The viral DNA then gets incorporated into host cell’s DNA and directs infected cells to produce new virus particles.

Long Answer Questions

Question. Mention the name of the causal organism, symptoms and the mode of transmission of the disease amoebiasis. 
                                             OR
(a) Name the protozoan parasite that causes amoebic dysentery in humans.
(b) Mention two diagnostic symptoms of the disease.
(c) How is this disease transmitted to others?
                                OR
(a) Name the agent that causes amoebiasis and the human body organ that it infects.
(b) Write the symptoms and the mode of transmission of the disease. 
Answer. Amoebic dysentery (Amoebiasis)
• It is caused by a protozoan endoparasite, Entamoeba histolytica, found in large intestine of humans.
• Housefly acts as mechanical carrier and transmits the parasite from faeces of infected person to the food.
• Infection takes place through food and water contaminated by faecal matter.

Question. A doctor prescribed morphine as a sedative and pain killer to your cousin who had undergone surgery. Even after recovery, he craved for the prescribed medicine. What do you conclude about his condition, had he continued with the same medication? After appraising yourself, what measures will you suggest to him to overcome this problem? Briefly explain any two.
Answer. His condition is drug dependence. It is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome if regular dose of drugs is abruptly discontinued. Because of perceived benefits, drugs are frequently used repeatedly from which the person may not be able to get out.
Following measures can be taken to overcome this problem:
(i) Education and counseling to face problems and stresses and to channelise the energy into healthy pursuits like reading, music, yoga and other extracurricular activities.
(ii) Seeking help from parents to guide the person appropriately and immediately.
(iii) Seeking professional and medical help to the person to get rid of the problem completely with sufficient efforts and will power a(ny two).

Question. Name the form of Plasmodium that gains entry into the human body. Explain the different stages of its life cycle in the human body. 
Answer. Plasmodium vivax gains entry into the human body.
Malaria
• It is caused by a protozoan Plasmodium (P. vivax, P. malaria and P. falciparum).
• P. falciparum causes the most serious and fatal malignant malaria.
• The vector of Plasmodium is female Anopheles mosquito which transfers the sporozoites (infectious form).
• Treatment is by antimalarial drugs like quinine, chloroquin.
• Malaria can be prevented by killing mosquitoes by spraying DDT, BHC, etc., and using insect repellents, mosquito nets, etc.

Question. Malarial parasite ‘Plasmodium’ completes its life cycle in two hosts. Draw its complete life cycle and explain various stages it follows throughout its life. 
Answer. Stages:
(a) The stage in which the parasite enters in the body of humans through saliva of mosquito—sporozoite stage.
(b) Asexual reproduction of sporozoites in liver cells, resulting into bursting of those cells and releasing outside into the blood.
(c) Sporozoites infect RBCs, cause them to get burst and represented by repeated cycles of fever.
Released parasites also infect other RBCs.
(d) Parasites then follow sexual stage in RBCs which is called as ring signet stage and appears as a ring inside the RBCs under microscope. Usually presence of malarial parasite in humans is identified by pathologists by this stage.
(e) Female mosquito takes up gametocytes with the blood of host. Fertilisation and development takes place in the intestine of mosquito.
(f) From intestine, parasite comes to the salivary glands from where it reaches to human body and that is how the cycle continues.

Question. Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.
(a) What is a vaccine? Explain how does it impart immunity to the child against the disease.
(b) With the help of an example each, differentiate between active and passive immunity.
Answer. (a) Vaccination is the process of introduction of weakened or inactivated pathogens or proteins (vaccine) into a person to provide protection against a disease.
• Vaccines are weakened or inactivated pathogens or proteins introduced into a person to provide protection against a disease.
• Immunisation is the process by which the body produces antibodies against the vaccine (primary response) and develops the ability to neutralise pathogens during actual infection (secondary response).
• Vaccination provides immunisation after a time gap.
• Vaccination and immunisation are based on the property called ‘Memory’ of the immune system.
(b) Refer to Basic Concepts Point 9.

Question. To which category of cells do B-cells and T-cells belong? How do they differ from each other with reference to their formation and response to antigens?
Answer. B-cells and T-cells belong to the category of lymphocytes, i.e., leucocytes (WBC).
Differences between B-lymphocyte and T-lymphocyte

Question. Explain the process of replication of a retrovirus after it gains entry into the human body.
OR
(a) How does a Human Immunodeficiency Virus (HIV) replicate in a host?
(b) How does a HIV-infected patient lose immunity?
(c) List any two symptoms of this disease. 
Answer. (a)

(b) An HIV-infected patient loses immunity due to loss of T-lymphocytes.
(c) Symptoms are fever, diarrhoea, susceptibility to other diseases and prone to microbial infection. (Any two)

Question. Your school has been selected by the Department of Education to organise and host an interschool seminar on “Reproductive Health—Problems and Practices”. However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is “too embarrassing.”
Put forth four arguments with appropriate reasons and explanation to justify the topic to be very essential and timely. 
Answer. (i) The issue of puberty and adolescence need to be addressed effectively with the respective age group because many changes take place in the body during adolescence of which they are supposed to be aware of.
(ii) To bring in awareness about their reproductive health and its effect on their physical,emotional and social being.
(iii) To address the increase in sex abuse and sex crimes in our country.
(iv) Myths and misconceptions related to reproductive issues need to be cleared at the right time.

Question. Why do some adolescents start taking drugs? How can the situation be avoided?
Answer. The psychological attachment to certain effects such as euphoria and temporary feeling of well-being,associated with drugs and alcohol is called addiction.
• People take drugs/alcohol when not needed, but with repeated use, tolerance level of receptions in body increases; receptors thus respond to higher doses, leadinng to greater intake and addition.
For measures to avoid taking drug, Avoid undue pressure: Every child has his own choice and personality and hence should be respected and nurtured accordingly. They should not be forced to perform beyond their threshold limits, be in sports or studies, etc.
• Educating and counselling: Children should be educated and counselled to face problems, stresses,to accept disappointments and features as part of life. We shold put in efforts to channellise child’s energy into healthy pursuits like sports, reading, music, yoga etc.

Question. (a) Name and explain giving reasons, the type of immunity provided to the newborn by the colostrum and vaccinations.
(b) Name the type of antibody
(i) present in colostrum
(ii) produced in response to allergens in human body.
Answer. (a) Colostrum provides passive immunity, because the infant gets antibodies from the mother’s body directly for protection.Vaccinations provide active immunity because in this case microbes are injected into the body do develop immunity slowly.
(b) (i) IgA (ii) IgE

Question. What is the basic principle of vaccination? How do vaccines prevent microbial infections?
Name the organism from which hepatitis B vaccine is produced. 
Answer. Principle of vaccination is based on the property of ‘memory’ of immune system. In vaccination,a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body. The antigens generate primary immune response by producing antibodies along with forming memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, second time/subsequent time the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies. Hepatitis B vaccine is produced from yeast.

Question. (a) Why is there a fear amongst the guardians that their adolescent wards may get trapped in drug/alcohol abuse?
(b) Explain ‘addiction’ and ‘dependence’ in respect of drugs/alcohol abuse in youth.
Answer. (a) Adolescents are easily affected by (or are vulnerable to) peer pressure. Curiosity, need for adventure and excitement, and experimentation constitute common causes for motivation. A child’s natural curiosity motivates him/her to experiment. Television, movies, newspapers, internet also promote drug use.
(b) Addiction is the psychological attachment to certain effects such as euphoria or temporary feeling of well-being.
Dependence is the tendency of the body to show withdrawal syndrome or symptoms if regular doses of drug/alcohol is abruptly discontinued.

Question. (a) Name the types of lymphoid organs, lymph nodes and thymus are. Explain the role played by them in causing immune response.
(b) Differentiate between innate immunity and acquired immunity. 
Answer. (a) Thymus is primary lymphoid organ and lymph nodes are secondary lymphoid organs.
Thymus provides the microenvironment for immature lymphocytes to differentiate into antigen-sensitive lymphocytes.
Lymph nodes serve to trap the microorganisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the
activation of lymphocytes present there and cause the immune response.
(b)

Question. A team of students are preparing to participate in the interschool sports meet. During a practice session you find some vials with labels of certain cannabionoids.
(a) Will you report to the authorities? Why?
(b) Name a plant from which such chemicals are obtained.
(c) Write the effect of these chemicals on human body.
Answer. (a) Yes. Because these may be abused by sports person.
(b) Cannabis (sativa)
(c) Cannabinoids effect cardiovascular system of the body.

Question. (a) Name and explain giving reasons, the type of immunity provided to the newborn by the colostrum and vaccinations.
(b) Name the type of antibody
(i) present in colostrum
(ii) produced in response to allergens in human body.
Answer. (a) Colostrum provides passive immunity, because the infant gets antibodies from the mother’s body directly for protection.
Vaccinations provide active immunity because in this case microbes are injected into the body do develop immunity slowly.
(b) (i) IgA (ii) IgE

Question. (a) Cancer is one of the most dreaded diseases of humans. Explain ‘Contact inhibition’ and ‘Metastasis’ with respect to the disease.
(b) Name the group of genes which have been identified in normal cells that could lead to cancer and how they do so?
(c) Name any two techniques which are useful to detect cancers of internal organs.
(d) Why are cancer patients often given α-interferon as part of the treatment?
Answer. (a) Contact inhibition is the property of normal cells in which contact with other cells inhibits their uncontrolled growth.
Metastasis is the property in which tumour cells reach distant sites in the body, through blood.
(b) Proto oncogenes or Cellular oncogenes.
These genes when activated under certain condition could lead to oncogenic transformation of the cells.
(c) Biopsy/radiography/CT/MRI (Any two)
(d) α-interferon activates immune system and destroys the tumour.

Question. Name a human disease, its causal organism, symptoms (any three) and vector, spread by intake of water and food contaminated by human faecal matter.
Answer. (i) Typhoid
- It is caused by pathogenic bacterium Salmonella typhi.
- It is spread by contaminated food and water.
- It generally enters the small intestine and then migrates to other organs through blood.
Symptoms
(a) Constant high fever (39°C to 40°C) (b) Weakness (c) Stomach pain
(d) Loss of appetite (e) Constipation (f) Headache
(g) Intestinal perforation and death may occur in severe cases.
- Typhoid fever can be confirmed by Widal test.
- Mary Mallon, called Typhoid Mary, was a cook and a typhoid carrier who continued to spread the disease for several years through the food prepared by her, before it was discovered.

Amoebic dysentery (Amoebiasis)
- It is caused by a protozoan endoparasite, Entamoeba histolytica, found in large intestine of humans.
- Housefly acts as mechanical carrier and transmits the parasite from faeces of infected person to
- the food.
- Infection takes place through food and water contaminated by faecal matter.
Symptoms
(a) Abdominal pain      (b) Constipation
(c) Cramps                 (d) Stool with excess mucous and blood clots.

Filariasis/Elephantiasis
- It is caused by filarial worms, Wuchereria bancrofti and Wuchereria malayi.
- Female Culex mosquito is the vector.
Symptoms
(a) Blockage of lymph vessels of lower limbs resulting in swelling.
Lower limbs appear like legs of elephant, thus the name.
(b) Genital organs may also be affected, leading to deformation.

Question. (a) Name the causative agents of pneumonia and common cold.
(b) How do these differ in their symptoms ?
(c) Mention two symptoms common to both. 
Answer. (a) Pneumonia is caused by Streptococcus pneumoniae/Haemophilus influenzae and that of common cold is Rhinoviruses.
(b) Different symptoms:

(c) Common symptoms:
(i) In both the cases the infected person is inflicted with cough.
(ii) In both the cases the patient suffers from headaches.

Question. (a) How does the human body respond when vaccine is introduced into it ?
(b) It is said that vaccinations are a must for a healthy society. Justify. 
Answer. (a) B-cells assisted by T-cells produce antibodies against weakened antigens, which have been introduced as vaccine. These antibodies neutralise the pathogens (during actual infection) and also generate memory B-cells and T-cells.
(b) B and T memory cells recognise the pathogen in case of actual infection and produce antibodies to kill the pathogen. Thus the population will remain healthy if they are vaccinated prior to the infection.

Question. (a) Name the respective forms in which the malarial parasite gains entry into (i) Human body and (ii) Body of female Anopheles.
(b) Name the hosts where the sexual and the asexual reproductions of malarial parasites occur respectively.
(c) Name the toxin responsible for the appearance of symptoms of malaria in humans. Why do these symptoms occur periodically?
Answer. (a) (i) Sporozoite
(ii) Gametocytes.
(b) Sexual reproduction occurs in mosquito and asexual reproduction takes place in human body.
(c) The name of the toxin is haemozoin. Parasites after entering the fresh RBCs take 48 to 72 hours to complete the erythrocytic cycle, rupturing the erythrocytes. They then burst to release toxic substance called haemozoin and the symptoms like chill and high fever occurs periodically.

Question. (a) Name the stage of Plasmodium that gains entry into the human body.
(b) Trace the stages of Plasmodium in the body of female Anopheles after its entry.
(c) Explain the cause of periodic recurrence of chill and high fever during malarial attack in humans. 
Answer. (a) Plasmodium enters the human body as sporozoites.
(b) When a female Anopheles mosquito bites an infected person, the parasites enter the mosquito’s body and undergo further development. The parasites multiply within them to form sporozoites that are stored in salivary glands until their transfer to human body.
(c) The rupture of RBCs release a toxic substance called haemozoin, which is responsible for the chill and high fever recur.

Question. (a) Name a drug used (i) as an effective sedative and pain killer (ii) for helping patients to cope with mental illnesses like depression, but often misused.
(b) How does the moderate and high dosage of cocaine affect the human body?
Answer. (a) (i) Morphine
(ii) Lysergic acid diethyl amides (LSD).
(b) Cocaine team of students are preparing to participate in the interschool sports meet. During a practice session you find some vials with labels of certain cannabionoids.
(a) Will you report to the authorities? Why?
(b) Name a plant from which such chemicals are obtained.
(c) Write the effect of these chemicals on human body. 
Answer. (a) Yes. Because these may be abused by sports person.
(b) Cannabis (sativa)
(c) Cannabinoids effect cardiovascular system of the body.has a potent simulating action on central nervous system producing a sense of euphoria and increased energy. Excessive dosage of cocaine causes hallucinations.

ONE MARK QUESTION

1 What role do macrophages play in providing immunity to humans?

2 Recently chikungunya cases were reported from various parts of the country. Name the vector responsible.

3 How do neutrophils act as a cellular barrier to pathogens in humans?

4 Name the two types of cells in which the HIV multiplies after gaining entry into the human blood.

5 Given below are some human organs. Identify one primary and one secondary lymphoid organs: Liver,Thymus, Stomach,Thyroid, Tonsils

6 How does colostrums provide initial protection against diseases to new born infants? Give one reason.

7 Small allergens trigger sneezing and wheezing in human beings. What causes this type of response by the body?

8 A body of ten years had chicken pox. He is not exposed to have the same disease for the rest of his life. Mention how it is possible.

9 What type of virus causes AIDS? Name its genetic material.

10 Give the scientific name of the parasite that causes malignant malaria in humans.