12th Biology Paper Solutions Set 2 : CBSE All India Previous Year 2012

General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four Sections A, B, C and D. Section A contains 8 questions of one mark each, Section B is of 10 questions of two marks each, Section C is of 9 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 in one question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
Q1 :

How do the pollen grains of Vallisneria protect themselves? (1)


Answer :

Vallisneria is a water pollinated species. Pollen grains of Vallisneria have a protective mucilaginous coat that prevents the water from damaging the pollen grains.

Q2 :

Name the respective pattern of inheritance where F1 phenotype (1)

(a) does not resemble either of the two parents and is in between the two.

(b) resembles only one of the two parents.


Answer :

(a) Incomplete Dominance is the condition in which the F1 phenotype does not resemble both the parents and is in between the two.

(b) Complete Dominance is the condition in which the F1 phenotype resembles the dominant parent i.e one of the two parents.

Q3 :

Write the name of the following: (1)

(a) The most common species of bees suitable for apiculture

(b) An improved breed of chicken


Answer :

(a) Apis indica is the most common species of bee suitable for apiculture.

(b) Leghorn is an improved breed of chicken.

Q4 :

Mention the role of cyanobacteria as a biofertiliser. (1)


Answer :

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Q5 :

How is the entry of only one sperm and not many ensured into an ovum during fertilisation in humans? (1)


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Q6 :

Where is acrosome present in humans? Write its function. (1)


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Q7 :

State the significance of Coelacanth in evolution. (1)


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Q8 :

Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters? (1)


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Q9 :

(a) Where do the signals for parturition originate from in humans?

(b) Why is it important to feed the newborn babies on colostrums? (2)


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Q10 :

Given reasons for the following: (2)

(a) The human testes are located outside the abdominal cavity.

(b) Some organisms like honey-bees are called parthenogenetic animals.


Answer :

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Q11 :

(a) Mention the cause and the body system affected by ADA deficiency in humans.

(b) Name the vector used for transferring ADA-DNA into the recipient cells in humans. Name the recipient cells. (2)


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Q12 :

Name the source organism that possesses Taq polymerase. What is so special about the function of this enzyme? (2)


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Q13 :

State one advantage and one disadvantage of cleistogamy. (2)


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Q14 :

How did Ahmed Khan, plastic sacks manufacturer from Bangalore, solve the ever-increasing problem of accumulating plastic waste? (2)


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Q15 :

Name the source of cyclosporin-A. How does this bioactive molecule function in our body? (2)

OR

(a) Name the group of viruses responsible for causing AIDS in humans. Why are these viruses so named?

(b) List any two ways of transmission of HIV infection in humans, other than sexual contact.


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Q16 :

(a) Draw a neat labelled diagram of a nucleosome.

(b) Mention what enables histones to acquire a positive charge. (2)


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Q17 :

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. (2)


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Q18 :

Explain brood parasitism with the help of an example. (2)


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Q19 :

Differentiate between perisperm and endosperm giving one example of each. (3)


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Q20 :

How does industrial melanism support Darwin”™s theory of Natural Selection? Explain. (3)


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Q21 :

List the salient features of double helix structure of DNA. (3)

OR

How are the structural genes activated in the lac operon in E.coli?


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Q22 :

Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles. (3)


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Q23 :

(a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.

(b) Name the vector used for introducing the nematode specific gene in tobacco plant. (3)


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Q24 :

(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.

(b) What is the phenotype of the following: (3)

(i) IAi

(ii) i i


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Q25 :

(a) List any three ways of measuring population density of a habitat.

(b) Mention the essential information that can be obtained by studying the population of an organism. (3)


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Q26 :

How is the amplification of a gene sample of interest carried out using Polymerase Chain Reaction (PCR)? (3)


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Q27 :

(a) What is the programme called that is involved in improving success rate of production of desired hybrid and herd size of cattle?

(b) Explain the method used for carrying this programme for cows. (3)


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Q28 :

(a) Explain the significance of ecological pyramids with the help of an example.

(b) Why are the pyramids referred to as “upright”™ or “inverted”™ (5)

OR

(a) Explain giving reasons why the tourists visiting Rohtang Pass or Mansarovar are advised to resume normal “active life”™ only after a few days of reaching there.

(b) It is impossible to find small animals in the polar regions. Give reasons.


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Q29 :

Describe Frederick Griffith”™s experiment on Streptococcus pneumonia. Discuss the conclusion he arrived at. (5)

(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.

(b) State the laws of inheritance that can be derived from such a cross.

(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?


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Q30 :

The following is the illustration of the sequence of ovarian events “a” to “i” in a human female:

(a) Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.

(b) Specify the endocrine function of corpus luteum. How dies it influence the uterus? Why is it essential?

(c) What is the difference between “d” and “e”?

(d) Draw a neat labeled sketch of Graafian follicle. (5)

OR

(a) Why is fertilization in an angiosperm referred to as double fertilisation? Mention the ploidy of the cells involved.

(b) Draw a neat labeled sketch of L.S. of an endospermous monocot seed.


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12th Biology Paper Solutions Set 3 : CBSE Delhi Previous Year 2013 will be available online in PDF book soon. The solutions are absolutely Free. Soon you will be able to download the solutions.