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Board Paper of Class 12-Science 2004 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

    Name the condition in humans in which the blood cholesterol content becomes abnormally high.

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  • Question 3

    Many villagers near Industrial area suffer from "blue baby syndrome". How is this problem caused?

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  • Question 4

    A cardiologist observed an elevated ST Segment in the ECG of a patient. What is it indicative of?

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  • Question 5

    Why is quarantine a must before introduction of a plant species from a different country?

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  • Question 6

    What is meant by apoplast pathway? Why does it occur in cortex and not in endodermis?

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  • Question 7

    Where is pneumotoxic centre located in humans? What is its significance in breathing?

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  • Question 8

    How is a disease-resistant plant selected for successful breeding?

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  • Question 9

    Why is the process of fertilisation in a flowering plant referred to as double fertilisation? Explain.

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  • Question 10

    Name the watery fluid secreted from Brunner's gland in the duodenum. Mention its any two characteristics. What role does it play inside the duodenum?

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  • Question 11

    How is opening and closing of stomata controlled? Explain.

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  • Question 12

    Why is the length of a food chain in an ecosystem generally limited to 3 − 4 trophic levels? Explain with an example.

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  • Question 13

    In what form do the terrestrial reptiles excrete their nitrogenous waste? How is this kind of excretion advantageous to the land vertebrates which lay shelled eggs?

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  • Question 14

    Explain briefly how computed tomography (CT) helps the doctors in pinpointing the defects in the patient's body.

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  • Question 15

    What is eutrophication? Explain with reference to aquatic ecosystem.

    OR

    Name any two source organisms of agar. List any four areas in which agar has wide application.

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  • Question 16

    Name the two groups of nephrons on the basis of their position in the kidney. How are they different from each other?

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  • Question 17

    How is the halophyte Rhizophora adapted to survive in its habitat? Explain.

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  • Question 18

    When and why does photo-respiration take place in plants? How does this process result in a loss to the plant?

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  • Question 19

    Explain the sliding filament theory of muscle contraction.

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  • Question 20

    What is special of "FlavrSavr" variety of tomato? Why is it preferred to its normal native variety?

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  • Question 21

    Draw a labelled sketch of L.S. of a human grinding tooth fixed in the socket. 

     

    OR

     

    Draw a schematic diagram to show the spinal reflex arc. Label the components of the pathway.

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  • Question 22

    Name the organism involved in symbiotic nitrogen fixation. What are the components needed for this process? Explain their role.

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  • Question 23

    Differentiate between inbreeding and heterosis. The outcome of which one is superior in performance and why?

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  • Question 24

    What is the optimum percentage of forest area recommended by the National Forest Policy (1988) for the plains and the hills respectively? List any four problems caused due to deforestation.

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  • Question 25

    Why is the human placenta referred to as haemochorial type? Name the hormone it secretes to facilitate parturition.

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  • Question 26

    Where does Calvin cycle take place in chloroplast? Explain the cycle.

     

    OR

     

    Where is electron transport system operative in mitochondria? Explain the system highlighting the role of oxygen.

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  • Question 27

    Describe the hormonal control of the reproductive system in human male.

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  • Question 28

    Define totipotency. Explain the two different routes of regenerating plantlets from callus culture.

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