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Board Paper of Class 12-Science 2015 Biology Delhi(SET 2) - Solutions

General Instructions :
(i) There are a total of 26 questions and five sections in the question paper, All questions are compulsory.
(ii) Section A contains question number 1 to 5, Very Short Answer type questions of one mark each.
(iii) Section B contains question number 6 to 10, Short Answer type I questions of two marks each.
(iv) Section C contains question number 11 to 22, Short Answer type II questions of three marks each.
(v) Section D contains question number 23, Value Based Question of four marks.
(vi) Section E contains question number 24 to 26, Long Answer type questions of five marks each.
(vii) There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examinee is to attempt any one of the questions out of the two given in the question paper with the same question number.
  • Question 2
    State a reason for the increased population of dark coloured moths coinciding with the loss of lichens (on tree barks) during industrialization period in England. VIEW SOLUTION
  • Question 3
    Indiscrimate diagnostic practices using X-rays etc., should be avoided. Give one reason. VIEW SOLUTION
  • Question 4
    Name the transcriptionally active region of chromatin in a nucleus. VIEW SOLUTION
  • Question 5
    A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms for experiments with shorter life cycle. Provide a reason. VIEW SOLUTION
  • Question 6
    Many fresh water animals can not survive in marine environment. Explain.
     
    OR

    How are productivity, gross productivity, net primary productivity and secondary productivity interrelated ? VIEW SOLUTION
  • Question 7
    Name any two common Indian millet crops. State one characteristic of millets that has been improved as a result of hybrid breeding so as to produce high yielding millet crops. VIEW SOLUTION
  • Question 8
    Mention a product of human welfare obtained with the help of each one of the following microbes :
    (a) LAB
    (b) Saccharomyces cerevisiae
    (c) Propionibacterium shermanii
    (d) Aspergillus niger VIEW SOLUTION
  • Question 9
    Explain mechanism of sex-determination in birds. VIEW SOLUTION
  • Question 10
    After a brief medical examination a healthy couple came to know that both of them are unable to produce functional gametes and should look for an 'ART' (Assisted Reproductive Technique). Name the 'ART' and the procedure involved that you can suggest to them to help them bear a child. VIEW SOLUTION
  • Question 11
    What is adaptive radiation ? When can adaptive radiation be referred to as convergent evolution ? Give an example. VIEW SOLUTION
  • Question 12
    A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible. VIEW SOLUTION
  • Question 13
    (a) A DNA segment has a total of 1,500 nucleotides, out of which 410 are Guanine containing nucleotides. How many pyrimidine bases this segment possesses ?

    (b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer. VIEW SOLUTION
  • Question 14
    Name the stage of human embryo at which it gets implanted. Explain the process of implantation. VIEW SOLUTION
  • Question 15
    A non biology person is quite shocked to know that apple is a false fruit, mango is a true fruit and banana is a seedless fruit. As a biology student how would you satisfy this person ? VIEW SOLUTION
  • Question 16
    Enlist the steps involved in inbreeding of cattle. Suggest two disadvantages of this practice. VIEW SOLUTION
  • Question 17
    Choose any three microbes, from the following which are suited for organic farming which is in great demand these days for various reasons. Mention one application of each one chosen.

    Mycorrhiza; Monascus; Anabaena; Rhizobium; Methanobacterium; Trichoderma. VIEW SOLUTION
  • Question 18
    Draw a labelled sketch of sparged-stirred-tank bioreactor. Write its application. VIEW SOLUTION
  • Question 19
    Following the collision of two trains a large number of passengers are killed. A majority of them are beyond recognition. Authorities want to hand over the dead to their relatives. Name a modern scientific method and write the procedure that would help in the identification of kinship. VIEW SOLUTION
  • Question 20
    Recombination DNA−technology is of great importance in the field of medicine. With the help of a flow chart, show how this technology has been used in preparing genetically engineered human insulins. VIEW SOLUTION
  • Question 21

    Many plant and animal species are on the verge of their extinction because of loss of forest land by indiscriminate use by the humans. As a biology student what method would you suggest along with its advantages that can protect such threatened species from getting extinct ?

    OR

    "Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body." Explain.

    VIEW SOLUTION
  • Question 22

    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 cannabinoids.

    (a) Will you report to the authorities? Why?

    (b) Name of a plant from which such chemicals are obtained.

    (c) Write the effect of these chemicals on human body.

    VIEW SOLUTION
  • Question 23
    Since October 02, 2014 "Swachh Bharat Abhiyan" has been launched in our country.
    (a) Write your views on this initiative giving justification.
    (b) As a biologist name two problems that you may face while implementing the programme in your locality.
    (c) Suggest two remedial methods to overcome these problems. VIEW SOLUTION
  • Question 24
    "Analysis of age-pyramids for human population can provide important inputs for long-term planning strategies." Explain.

    OR

    Describe the advantages for keeping the ecosystems healthy. VIEW SOLUTION
  • Question 25
    A flower of brinjal plant following the process of sexual reproduction produces 360 viable seeds.
    Answer the following questions giving reasons:
    (a) How many ovules are minimally involved?
    (b) How many megaspore mother cells are involved?
    (c) What is the minimum number of pollen grains that must land on stigma for pollination?
    (d) How many male gametes are involved in the above case?
    (e) How many microspore mother cells must have undergone reduction division prior to dehiscence of anther in the above case?

    OR

    Describe the changes that occur in ovaries and uterus in human female during the reproductive cycle. VIEW SOLUTION
  • Question 26
    Explain the genetic basis of blood grouping in human population.

    OR

    How did Hershey and Chase established that DNA is transferred from virus to bacteria? VIEW SOLUTION
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