Class 12 Biology: CBSE Sample Question Paper- Term II (2021-22)- 1 | Sample Papers for Class 12 Medical and Non-Medical PDF Download

Class-XII

Max. Marks: 35

General Instructions :

1. All questions are compulsory.
2. The  question  paper  has  three  sections  and  13  questions.  All  questions  are compulsory.
3. Section–A has 6 questions of 2 marks each; Section–B has 6 questions of 3 marks each; and Section–C has a case-based question of 5 marks.
4. There  is  no  overall  choice.  However,  internal  choices  have  been  provided  in some questions. A student has to attempt only one of the alternatives in such questions.
5. Wherever necessary, neat and properly labelled diagrams should be drawn.

Q.1. Name one airborne and a waterborne disease in humans. List one specific symptom of each one of them. 

Air-borne diseases : Tuberculosis (TB), Influenza.
Symptoms : Pain and difficulty in breathing/ coughing.
Water-borne diseases : Diarrhoea, Typhoid.

Symptoms : Loose motions/ Watery stool.

Q.2. The given diagram shows the typical signs of malarial disease. 

Give the scientific name of the parasite that causes malaria in humans. What causes chills in humans during malarial attack.

Name any two secondary lymphoid organs in a human body and state the function of any of them.

Plasmodium falciparum. The haemozoin released in blood plasma induces high fever and shivering.

OR

Spleen, lymph nodes, tonsils, Peyer’s patches of small intestine, vermiform appendix.
Function of 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. 

Q.3. Study the given chemical structure and identify the name. From which part of the plant it is obtained?

It is the chemical structure of a cannabinoid  molecule. Cannabinoids are obtained from the inflorescence of the plant Cannabis sativa.

Q.4. Medically it is advised to all the young mothers that breast-feeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer.

Yes.
Provides nutrition (calcium, fats, lactose) / provides (passive) immunity / provides antibodies / Ig A.
Breast feeding is recommended during the initial period of an infant’s growth as :
(a) It provides passive immunity to the baby through colostrum.
(b) It provides a balanced nutrition to the baby.
(c) Also, it protects the baby from allergens.

Q.5. Plants that inhabit a rain-forest are not found in a wetland. Give reason.

Plants that inhabit a rain forest are not adapted to survive in aquatic conditions / wetlands.
Plants are conformers / stenothermal / cannot maintain constant internal environment/ temperature / osmotic concentration of the body fluids affects kinetics of enzymes through basal metabolism / activity and other physiological functions of the organisms.

Q.6. What will happen to a well growing herbaceous plant in the forest if it is transplanted outside the forest in a park?

Of the four major causes for the loss of biodiversity (Alien species invasion, habitat loss and fragmentation, over-exploitation and co-extinctions), which according to you is the major cause for the loss of biodiversity? Give reason in support.

In forest ecosystem, tall trees of forest plants controls the light condition, that is, intensity, duration and quality of light at the ground. A well growing herbaceous plant in forest receive less intensity duration and quality of light, but when it is transplanted in a park outside its natural habitat, the light will be received uninterrupted. So, due to change in its microclimate, it may not survive.

OR

Loss of habitat and fragmentation occur due to clearing and over-exploitation of forest areas for agriculture, urbanization and industrialization. It is the major cause for the loss of biodiversity because :
(a) It results in destruction of natural habitats.
(b) Large habitats are broken up into small fragments, due to which mammals and birds which require large territories and migratory habits are badly affected, leading to decline in population.

Q.7. Two children, A and B of age 4 and 5 years respectively visited a hospital with a similar genetic disorder. The girl A was provided with enzyme replacement therapy and was advised to revisit periodically for further treatment. The girl B was however, given a therapy that did not require revisit for further treatment.
(a) Name the ailments the two girls were suffering from?
(b) Why did the treatment provided to girl A required repeated visits?
(c) How was the girl B cured permanently?

A farmer while working on his farm was bitten by a poisonous snake. The workers in the farm immediately rushed him to the nearby health centre. The doctor right away gave him an injection to save his life. What did the doctor inject and why? Explain.

(a) Adenosine deaminase (ADA) deficiency.
(b) (In Enzyme Replacement Therapy) functional ADA is introduced to the patient (by injection), this therapy is not completely curative / enzyme can act only for a limited time period.
(c) As there is no permanent cure at the age of five, the gene isolated from bone marrow cells producing ADA is introduced into the cells of girl-B at early embryonic stages which acted as a permanent cure.
Detailed Answer :
(a) They were suffering from adenosine deaminase (ADA) deficiency.
(b) Girl A was given enzyme replacement therapy, in which lymphocytes isolated from patient's blood are cultured in- vitro.
A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires a periodic infusion of such genetically engineered lymphocytes.
(c) Girl B was treated with gene therapy, in which the gene isolated from bone marrow cells producing ADA is introduced into cells at early embryonic stages, which is a permanent cure.

OR

(a) Antitoxin / Antivenoms / Preformed antibodies.
(b) Whenever quick immune response is required, we need to directly inject preformed antibodies / Antitoxins.
(c) To neutralize the effect of snake venom quickly, passive immunity is provided. 

Q.8. A group of youth were having a ‘rave party ‘ in an isolated area and was raided by police. Packets of ‘smack‘ and syringes with needles were found littered around.
(a) Why is taking ‘smack‘ considered an abuse?
(b) Write the chemical name of ‘smack‘ and the name of its source plant.
(c) Syringes and needles used by the youth for taking the drug could prove to be very fatal. Why ? 

(a) Because an addictive substance causes drug dependence and affects nervous system / used in amounts or frequencies that impairs ones physical and physiological or psychological functions.
(b) Diacetyl-morphine
Papaver somniferum / poppy plant / opium poppy.
(c) They can transmit serious infections i.e., transmission of HIV infections or AIDS or Hepatitis.

Q.9. Explain the roles of the following in Biotechnology:
(a) Restriction endonuclease
(b) Gel-Electrophoresis
(c) Selectable markers in pBR322.

(a) Cuts at specific position within the DNA / cuts DNA at specific nucleotide / cuts at palindromic nucleotide sequence.
(b) Method of separation of DNA fragments (under the influence of electric field).
(c) Helps in identifying and eliminating non-transformants from transformants / selection of transformants.

Detailed Answer :

(a) The enzyme restriction endonuclease recognises the base sequence at palindrome sites in DNA and cut it's strand.
(b) Gel electrophoresis is a technique of separation of charged molecules under the influence of an electric field. With the help of the gel electrophoresis technique, DNA fragments get separated according to their size through the pores of agarose gel.
(c) Selectable marker (marker gene) helps to select the transformants and eliminate the non-transformants.
E.g., antibiotic resistance genes.

Q.10. (a) India has greater ecosystem diversity than Norway.” Do you agree with the statement ? Give reasons in support of your answer.
(b) Write the difference between genetic biodiversity and species biodiversity that exists at all levels of biological organization.

(a) Yes
India / tropical region :
(i) are less seasonal / more constant / more predictable.
(ii) promote niche specialisation leading to greater biodiversity.
(iii) Species diversity increases as we move towards equator. (iv) More number of species exist.

Norway / temperate region : 
(i) more seasonal / less constant / less predictable.
(ii) do not promote niche specialisation leading to low bio-diversity.
(iii) Species diversity decreases as we move away from the equator.
(iv) Less number of species exist.

(b) (i) Genetic diversity : Diversity / variation within a species over its distributional range/ (same explanation with the help of a correct examples)
(ii) Species diversity : Diversity / variation at a species level (same explained with the help of a correct example).
Detailed Answer :
(a) Yes, India has greater ecosystem diversity than Norway. It is because India lies primarily in the tropical and sub-tropical zone while Norway lies near the Arctic region. This exposes the India to greater amount of sunlight and thus a greater level of ecosystem diversity.
(b) Difference between genetic diversity and species diversity :

Q.11. Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible to conserve all their biological wealth. On a global basis, this problem has been addressed by renowned conservationists. They identified for maximum protection for certain ‘biodiversity hotspot’ regions. According to Conservation International at present, there are 36 biodiversity rich areas in the world that have been qualified as hotspots.
(a) State any two criteria for determining biodiversity hotspots.
(b) Name any two hotspots designated in India.

(a) Criteria for determining biodiversity hot spots are :

• High levels of species richness.
• High degree of endemism.

(b) Hotspots in India - Western Ghats, Himalaya (Indo-Burma/Sunderland to be accepted)

Q.12. When the gene product is required in large amounts, the transformed bacteria with the plasmid inside the bacteria are cultured on a large scale in an industrial fermenter which then synthesizes the desired protein. This product is extracted from the fermenter for commercial use.
(a) Why is the used medium drained out from one side while fresh medium is added from the other? Explain.
(b) List  any  four  optimum conditions for achieving  the  desired  product  in  a bioreactor.

(a) This is to maintain the cells in the medium in their log/exponential phase. This is physiologically the most active phase.
(b) Temperature, pH, substrate and oxygen are the four optimum conditions required for achieving the desired product in a bioreactor.

Q.13. Around twenty years ago, Bt cotton was introduced in India. This cotton crop is a plant variety of genetically modified cotton. Strains of the bacterium Bacillus thuringiensis produce toxins that are harmful for a variety of insects. The aim of introducing Bt cotton to India was to reduce the amount of insecticide needed in farming cotton.
Since, the introduction of this plant, Bt cotton has been adopted widely across India. Today, most cotton growing industries in India uses Bt technology. 
(a) Name the insect that attacks cotton crops and can lead to a lot of damage to the crop. How has Bt cotton plants overcome this problem and saved the crop? Explain.
(b) Explain the role of gene Cry I Ab.

The Green Revolution in India began in the mid-1960s marking a transition from traditional agriculture in India and the introduction of high-yielding varieties of seeds and the associated agricultural techniques. The need for introducing the Green Revolution in India arose due to a shortage of food-grains in part due to the legacy of colonial regime. The government of India post-independence wanted to make India self-dependent in terms of food-grain production and these efforts coincided with the development of high-yielding varieties of seeds of wheat developed by Norman Borlaug and his associates in Mexico. These seeds also necessitated changes in farming techniques such as the addition of fertilizers and pesticides and greater use of irrigation. High yielding varieties of seeds were first introduced in India in the states of Punjab, Haryana and parts of western Uttar Pradesh.
The green revolution did effectively solve India’s problem of food-grain shortage after it was introduced in India, although in the second wave of the Green Revolution in the 1980s, there was however, a slight reduction in production as compared to the first wave. Thus, there is a need for another green revolution.
(a) Name the technique which will help in increasing the yield of crops.
(b) Name any two genetically modified crops.
(c) What is golden Rice’?
(d) Name a natural genetic engineer.

(a) Cotton bollworm is the insect that attacks cotton crops and causes a lot of damage to the crop.
Bt cotton plants are GMOs containing the active Cry gene from Bacillus thuringiensis, which form protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. These proteins are present in inactive form called protoxin, but become active toxin in the alkaline pH of the insect gut. The activated toxin binds to the surface of midgut epithelial cells and creates pores that causes cell swelling and lysis and eventually causes the death of the insect.
(b) The protein coded by gene cryI Ab controls corn borer.

OR

(a) Genetic engineering (Recombinant DNA technology).
(b) (i)  Bt cotton
(ii) ‘Flavr Savr Tomato’
(c) Golden rice is a transgenic variety of rice (Oryza sativa) that contains good quantities of 3-carotene (provitamin A – inactive state of vitamin). Since, the grains of the rice are yellow in color due to 3-carotene, the rice is called golden rice.
(d) Agrobacterium tumefaciens.