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Board Paper of Class 12-Science 2007 Biology Delhi(SET 1) - Solutions

General Instructions:
 (i) All questions are compulsory.
(ii) This question paper consists of four sections A, B, C and D.
Section A contains 5 questions of one mark each.
Section B is of 10 questions of two marks each.
Section C is of 10 questions of three marks each and
 Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
  • Question 1

    What is the importance of the epiglottis in human body? 

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  • Question 2

    What happens to the glycogen concentration in the liver cells when the level of adrenaline increases in the blood stream of humans? 

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  • Question 3

    Mention the scientific term used for modified form of reproduction in which seeds are formed without fusion of gametes.

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  • Question 4

    What does ecological niche of an organism represent?

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  • Question 5

    It was diagnosed by a specialist that the immune system of the body of a patient has been suppressed. Name the disease the patient has been suffering from and its causative agent.

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  • Question 6

    Where are casparian strips located in a plant body and what are they made up of? Mention its function.

    OR

    What is respiration quotient (RQ)? Under what conditions will the value of RQ be 1? Explain.

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  • Question 7

    What is resting membrane potential of a neuron? What is the role of sodium potassium pumps in maintaining it?

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  • Question 8

    Draw a diagram of external view of a human brain. Label the frontal lobe, temporal lobe, occipital lobe and cerebellum.

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  • Question 9

    How is the milk production regulated by hormones in human female? Explain.

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  • Question 10

    Explain the significance of the auxin / cytokinin ratio in plant tissue culture.

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  • Question 11

    What does S-shaped pattern of population growth represent? How is J-shaped pattern different from it and why?

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  • Question 12

    What does secondary productivity in an ecosystem indicate? List any two factors by which productivity is limited in aquatic ecosystems.

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  • Question 13

    How do viruses enter plant body and spread to long distances within it? Mention any two ways by which viruses spread from one plant to another.

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  • Question 14

    In what form do plants absorb calcium from the soil? List any two calcium deficiency symptoms in plants.

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  • Question 15

    What is vernalisation? How is the process of vernalisation advantageous to plants?

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  • Question 16

    Explain the theory of capillarity of water translocation in plants. Can the theory explain translocation of water in 100 m tall trees? Give one reason.

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  • Question 17

    What is symbiotic nitrogen fixation? Name the two protein components needed for this process. Explain their role.

    OR

    List the various modes of heterotrophic nutrition in plants. Explain any two modes giving one example of each.

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  • Question 18

    What is biological magnification? Explain how DDT as a water pollutant undergoes biological magnification.

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  • Question 19

    What are exotic species? Explain with the help of two examples how the exotic species disturb the native species of an ecosystem.

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  • Question 20

    In what forms are nitrogenous wastes excreted in birds, humans and aquatic turtles respectively? Why so, explain?

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  • Question 21

    A patient was complaining of frequent urination, excessive thirst and dehydration. His fasting glucose level was found to be normal. Name the disease and its cause. Explain why such symptoms are occurring in this patient.

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  • Question 22

    Explain with the help of a suitable example for each of the following terms: (i) morphallaxis (ii) epimorphosis and (iii) compensatory regeneration.

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  • Question 23

    Describe the polygonum type of embryo sac. Why it is generally referred to as monosporic?

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  • Question 24

    What is obsessive-compulsive disorder? How is it different from borderline personality disorder? What are the two most common obsessions that affect adolescents?

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  • Question 25

    What is human leukocytes antigen complex? Explain its role in organ transplantation.

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  • Question 26

    Why do C4plants have dimorphic chloroplasts? Explain the different steps involved in C4photosynthetic carbon cycle in such plants. 

    OR

    Explain the electron transport system. Where does it occur in a mitochondrion and what is the role of oxygen in it?

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  • Question 27

    Explain the events that occur in the human heart during ventricular systole and ventricular diastole in a cardiac cycle. Name the heart sounds and mention how they are produced.

    OR

    What is oxygen−haemoglobin dissociation curve? Describe the role of red blood cells in the transport of oxygen and carbon dioxide by blood.

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  • Question 28

    Briefly explain the principle, procedure and the role of ELISA.

    OR

    What is somatic hybridisation? Explain the various steps involved in the process. Mention any two uses of somatic hybridisation.

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