Human Health and Diseases VBQs Class 12 Biology

VBQs for Class 12

VBQs Human Health and Diseases Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Human Health and Diseases Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Human Health and Diseases VBQs Class 12 Biology

Very Short Answer Type Questions

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. 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.
Detailed Answer:
Monocytes are motile and phagocytic leucocytes.
They destroy microbes / engulfs and destroys the antigen / microbes and constitute cellular barriers of innate immunity. 

Question. Thymus of a new born child was degenerating right from birth due to a genetic disorder.
Predict its two impacts on the health of the child. 
Answer :
Thymus provides micro-environment for the development and maturation of T-lymphocytes, its degeneration will weaken the immune system so the child will be prone to frequent infections.

Question. Name two types of cells which act as ‘cellular barriers’ to provide innate immunity in humans.
Answer :
(i) Polymorpho nuclear leucocytes (neutrophils).
(ii) Monocytes–A kind of lymphocyte. 

Question. Why is Gambusia introduced into drains and ponds ? 
Answer :
Gambusia is a type of fish that preys upon the larvae of mosquitoes. It is therefore introduced into drains and ponds to feed on mosquito larvae / to eliminate the vectors responsible for causing malaria. It thus helps in controlling malaria.

Question. Why is secondary immune response more intense than the primary immune response in humans ? 
Answer :
Body will have memory B cells of the first encounter / presence of antibodies developed during primary immune response. 

Question. When does a human body elicit an anamnestic response ?
Answer :
Anamnestic response is the secondary response which is elicited when our body encounters with the same antigen to which the body has previously encountered. 

Question. State two different roles of spleen in the human body. 
Answer :
Spleen is the secondary lymphoid organ that stores lymphocytes, it filters blood by trapping blood borne microbes by phagocytes and lymphocytes. It also acts as a large reservoir to store erythrocytes. 

Question. Name the category of disease in which ‘Rheumatoid arthritis‘ in human is put under.
Answer :
Auto-immune disease. 

Question. Suggest a method to ensure an anamnestic response in humans.
Answer :
Vaccination or Immunization (Active / passive) or weakened or inactive microbes or pathogens or proteins or antibodies introduced into the host body. 

Question. Trace the route of Sporozoite of Plasmodium when it enters the human body through the bite of infected female Anopheles mosquito till its entry into the R.B.C. 
Answer :
Sporozoites attack liver cells. 
Sporozoites reproduce asexually in liver cells bursting them and then reach RBC. 

Question. Name two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitization of its primary host.
Answer :
(i) Snail (ii) Fish. 

Question. Some allergens trigger sneezing and wheezing in human beings. What causes this type of response by the body ?
Answer :
Such type of response by the body is due to the exaggerated action of its immune system to certain antigens or allergen present in the environment.

Short Answer Type Questions

Question. Name any two secondary lymphoid organs in a human body and state the function of any of them.
Answer :
 Spleen, lymph nodes, tonsils, Peyer’s patches of small intestine, vermiform appendix.
They act as sites for interaction of lymphocytes with the antigen and cause immune response.
Function : Spleen : Trap blood-borne microorganisms and worn out RBCs, thus filters blood.
Lymph nodes : Trap the microorganisms / antigens (which happen to get into the lymph and tissue fluid). The trapped antigens activate lymphocytes and cause immune response. 

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.
Detailed Answer :
The infected female Anopheles is the carrier of malarial parasite called Plasmodium. When bitten by this carrier the liver is initially affected. The infective stage of Plasmodium is sporozoite which is injected into the blood by female anopheles.
From blood, the sporozoites reach the liver cells where they multiply in liver cells. The liver cells rupture and liberate the parasite in blood where they attack RBCs, multiply and cause their rupture. Rupture of RBCs is associated with the release of a toxin called as hemozoin, which causes chill and high fever recurring every 3-4 days.

Question. List the symptoms of Ascariasis. How does a healthy person acquire this infection ?
Answer :
 Ascariasis is a helminthic disease caused by common round worm – Ascaris lumbricoides. The main symptoms of ascariasis are muscular internal bleeding, muscular pain, anaemia, blockage of intestinal passage. (Any three) 
By intake of water, vegetables, fruits, foods contaminated with the eggs of parasite excreted along with faeces of infected person.

Question. Name the type of immunity a baby is born with.
How is it different from the one he gets from the mother’s milk after birth ?
Answer :
 Innate Immunity, Acquired Immunity that a baby acquires from his mother’s milk after birth is an example of passive Immunity. 
Detailed Answer :
Innate immunity is present at the time of birth.
Innate immunity is different from the immunity that a baby get from mother’s milk after birth because immunity acquired from mother’s milk is acquired or passive immunity.

Question. How does a vaccine for a particular disease immunize the body against that disease ?
Write the events that take place when a vaccine for any disease is introduced into the human body.
Why a person with cuts and bruises following an accident is administered tetanus antitoxin ? Give reasons. 
What is a vaccine ? How do they act to provide long term immunity to an individual who is vaccinated ?
Answer :
 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 second time. These memory cells show rapid and massive responses so that body become immune to this pathogen. 

Question. (i) Highlight the role of thymus as a lymphoid organ.
(ii) Name the cells that are released from the above mentioned gland. Mention how they help in immunity. 
Answer :
 (i) The thymus is a primary lymphoid organ which is a component of immune system in the body. Here the immature lymphocytes differentiate into mature lymphocytes and become antigen sensitive in thymus.
(ii) T- lymphocytes are released from thymus.
T-cells themselves do not secrete antibodies but help B-cells to produce antibodies and provide cell-mediated immunity (CMI). 

Question. Name the two special types of lymphocytes in humans. How do they differ in their roles in immune response ?
Answer :
 B-lymphocytes, T-lymphocytes are the two special types of lymphocytes. 
B-cells produce pathogen specific antibodies and provide humoral immune response. 
T-cells help the B-cells to produce antibodies to fight with the pathogens and are responsible for cell mediated immunity. 

Question. Name any two organisms that are responsible for ringworms in humans. Mention two diagnostic symptoms. Name the specific parts of the human body where these organisms thrive and explain why ?
(i) Name any two causative organisms responsible for ringworm.
(ii) State any two symptoms of the disease.
Answer :
 Ringworm is caused by fungi Trichophyton and Epidermophyton and Microspermum.
Dry, scaly lesions appears on the body. These lesions are accompanied by intense itching.
The pathogen thrive in skin folds, nails and groins because the heat and moisture are favourable at these regions. 

Question. How do interferons protect us ?
Answer :
 Interferons are antiviral agents produced by virus infected cells and can fight tumors. The virusinfected cells stimulate neighbouring cells to release antiviral proteins by releasing interferons. Thus, interferons protect non-infected cells from further viral infections by creating cytokine barriers. 

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

Human Health and Diseases VBQs Class 12 Biology

Answer : A–antigen binding site.
B–variable region.
C–constant region.
D–light chain.
E–heavy chain (constant region).
F–disulphide bond. 

Question. The figure given below represents a molecule present in the body of a mammal –

Human Health and Diseases VBQs Class 12 Biology

a) Name the parts labeled ‘a’ and ‘b’ in the molecule shown above.
b) Name the type of cells that produce this molecule.
Answer :
 a) a- Antigen binding site.
b- Light chain. ½ + ½
b) B-lymphocytes (B- cells). 

Question. Name the bacterium that causes typhoid. Mention two diagnostic symptoms. How is this disease transmitted to others ?
Answer :
 Salmonella typhi.
Constipation, stomach pain, headache, weakness, loss of appetite, high fever.
The disease is transmitted through contaminated food or water. 

Question. State the functions of primary and secondary lymphoid organs in humans.
Answer :
 (i) Bone marrow is the main lymphoid organ where all types of blood cells including lymphocytes are formed.
(ii) The lymphocytes migrate to secondary lymphoid organs (e.g. spleen, lymph nodes, Peyer’s patches of small intestine), which interact with the antigen and proliferate to form a clone. 

Question. Differentiate between benign and malignant tumours.
Answer :

Human Health and Diseases VBQs Class 12 Biology

Question. (i) Why is mother’s milk considered very essential for the healthy growth of infants ? 
(ii) What is the milk called that is produced in the initial days of lactation ?
Answer :
 (i) The milk secretion has nutrients and contain antibodies Ig A, immunoglobulin A or Ig A provide passive immunity.
(ii) Colostrum. 

Question. On a visit to a Hill station, one of your friends suddenly became unwell and felt uneasy.
(i) List two symptoms you would look for to term it to be due to allergy.
(ii) Explain the response of the body to an allergy.
(iii) Name two drugs that can be recommended for immediate relief. 
Answer :
(i) Sneezing, watery eyes, running nose, difficulty in breathing. 
(ii) Body releases antibodies, lgE type and chemicals like histamine and serotonin from mast cells which produce symptoms of allergy. 
(iii) Anti histamine, adrenalin, steroids.

Question. State the three characteristics of Acquired Immunity. List the different ways by which it can be attained by humans.
Answer : Characteristics of Acquired Immunity :
Pathogen specific / characterized by memory / Acquired after birth / are of two types : Active and passive/humoral and cell mediated/includes primary response and secondary response.
Way by which it can be attained by humans:
Active Immunity by encountering a pathogen / virulent microbe/suffering from contagious disease. 
Passive Immunity through immunization / readymade antibodies. 
Detailed Answer :
Acquired immunity is pathogen specific. It is not present since birth. It develops during an individual’s life time. It is characterized by memory of the first encounter with the pathogen, which helps in producing intensive secondary response when the pathogen attacks second time. It has the ability to distinguish different types of foreign molecules or antigens. It is of two types: (a) Active immunity which develops in the body when it is exposed to the antigens or the pathogens and (b) Passive immunity which is bestowed by antibodies directly given to the body.
Active immunity may be attained by the humans by introducing the pathogen either during immunization or by any infection, while passive immunity develops by readymade antibodies e.g. the antibodies received by foetus from mother.
The cells which are responsible for producing acquired immune response are T-lymphocytes and B-lymphocytes. They produce antibodies which defend the body against the pathogens.

Question. A 17-year old boy is suffering from high fever with profuse sweating and chills. Choose the correct option from the following diseases which explains these symptoms and rule out the rest with adequate reasons.
(a) Typhoid (b) Viral Fever (c) Malaria
Answer :
(a) If the boy is suffering from typhoid then he should have sustained high fever (39° to 40°C), weakness, stomach pain, constipation and headache. So, it cannot be typhoid. 
(b) If the boy is suffering from viral fever, he will suffer from high fever, joint pain, weakness, and headache, So, it cannot be viral fever. 
(c) If the boy is suffering from malaria, he should have high fever recurring with profuse sweating every three to four days associated with chills and headache. There is a possibility
that he is suffering from Malaria because high fever associated with chills is possible with malaria. 

Question. (i) It is generally observed that the children who had suffered from chicken-pox in their childhood may not contract the same disease in their adulthood. Explain giving reasons the basis of such immunity in an individual. Name this kind of immunity. 
(ii) What are interferons ? Mention their role.
Answer :
(i) The first infection of chicken pox produce a primary response and antibodies are generated against chicken pox virus, subsequent encounter with the same virus elicits a highly intensified secondary response, due to the memory cells formed during the first encounter, active immunity. 
(ii) Proteins secreted by viral infected cells, which protects non infected cells from viral infection / when α –interferon is given to cancer patient (it activates immune system), destroys tumour. 
Detailed Answer :
(i) There are high chances that the people who have suffered from chickenpox in their childhood may not contract the disease again.
This is due to acquired immunity which is characterised by memory. Acquired immunity is pathogen specific. When a pathogen for the first time infects a person it produces primary immune response which is of low intensity.
When the same pathogen attacks again, highly intensified secondary (anamnestic) response is generated, thereby preventing the occurrence of disease.
(ii) Interferons are glyco-proteinaceous substances secreted by virus-infected dead animal cells.
These interferons protect the non-infected cells from getting infected by inhibiting viral replication.

Question. How does the HIV breakdown the immune system of the AIDS patients ?
Answer :
(i) Virus enters in macrophages,
(ii) RNA genome replicates to form viral DNA with help of reverse transcriptase,
(iii) Viral DNA gets incorporated into host cells DNA to produce virus particles,
(iv) HIV enters into helper ‘T’ lymphocytes and produces progeny virus,
(v) Which are released in the blood and attack other helper ‘T’ lymphocytes, (vi) This leads to progressive decrease in number of helper ‘T’ lymphocytes and the person starts suffering from infections (loss of immunity).