12th Biology Paper Solutions Set 3 : CBSE Abroad Previous Year 2015

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.
Q1 :

How does a degenerate code differ from an unambiguous one ?


Answer :

 

Degenerate Code Unambiguous Code
It means that different codons code for a single specific amino acid. It means that one codon codes for a single specific amino acid.
Example: Both GAA and GAG code for glutamic acid.

Example: UGG only codes for tryptophan.

Q2 :

Meiosis is an essential event in the sexual life cycle of any organism. Give two reasons.


Answer :

Meiosis is an essential event in the sexual life cycle of any organism. It is because of the following two reasons:

  • It is a source of genetic variability in the sexually reproducing organisms (due to crossing over that occurs in pachytene stage).
  • It helps to conserve the chromosome number of species from generation to generation.

Q3 :

"Man can be a primary as well as a secondary consumer." Justify this statement.


Answer :

Man is an omnivore, that is, he can feed on both plants and animals. Thus, a man can be a primary consumer when he consumes plant products such as cereals, fruits and vegetables and he can be a secondary consumer when he consumes herbivores such as goat and sheep (in the form of their meat). Thus, a man can be placed at the second as well as the third trophic level of the food chain.

Q4 :

Write the hypothetical proposals put forth by Oparin and Haldane.


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Q5 :

Write the function of RNA polymerase II.


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Q6 :

Suggest two advantages to a farmer for using apomictic seeds of hybrid varieties.


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Q7 :

Why did T. H. Morgan select Drosophila melanogaster to study sex linked genes for his lab experiments ?


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Q8 :

What is joint forest management ? How can it help in conservation of forests ?


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Q9 :

Differentiate between outbreeding and outcrossing.

OR

Bottled fruit juices are clearer as compared to those made at home. Explain.


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Q10 :

How does a desert plant adapt to the dry, warmer environmental conditions ?


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Q11 :

What is amniocentesis ? Justify the statutory ban on it.


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Q12 :

Draw a diagrammatic, labelled sketch of a sectional view of human ovary.


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Q13 :

Explain divergent evolution with two examples. 


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Q14 :

(a) Name the kind of diseases/disorders that are likely to occur in humans if
    (i) mutation in the gene that codes for an enzyme phenyl alanine hydrolase occurs,
    (ii) there is an extra copy of chromosome 21,
    (iii) the karyotype is XXY.
(b) Mention any one symptom of the diseases/disorders named above.


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Q15 :

How was a heavy isotope of nitrogen used to provide experimental evidence to semi-conservative mode of DNA-replication ?


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Q16 :

One of the major contributions of biotechnology is to develop pest-resistant varieties of cotton plants. Explain how it has been made possible.


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Q17 :

(a) State any two differences between phosphorus and carbon cycles in nature.
(b) Write the importance of phosphorus in living organisms.


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Q18 :

(a) Construct a pyramid of numbers by taking suitable examples for each trophic level in an ecosystem.
(b) Explain why a progressive decline is seen in the population size from the first to the fourth trophic level in the above pyramid.


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Q19 :

How can sewage be used to generate biogas ? Explain.


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Q20 :

Compare narrowly utilitarian and broadly utilitarian approaches to conserve biodiversity, with the help of suitable examples.


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Q21 :

Many copies of a specific gene of interest are required to study the detailed sequencing of bases in it. Name and explain the process that can help in developing large number of copies of this gene of interest.


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Q22 :

Prepare a flow chart in formation of recombinant DNA by the action of restriction endonuclease enzyme EcoRI.

OR

Name and explain the technique used for separating DNA fragments and making them available for biotechnology experiments.


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Q23 :

You have attended a birthday party hosted by one of your classmates. You found some guests at the party sitting in a corner making a lot of noise and consuming 'something'. After a while one of the boys from the group started screaming, behaving abnormally and sweating profusely. On enquiry you found that the group members were taking drugs.

(a) Would you inform your parents/school authorities ? Yes/No. Give reasons in support of your answer.

(b) Prepare a note to be circulated amongst the schoolmates about the sources and dangers of any two drugs.

(c) Write any two ways that you will suggest to your school principal so as to promote awareness amongst the youth against the use of these drugs.


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Q24 :

(a) State and explain the law of dominance as proposed by Mendel.
 

(b) How would phenotypes of monohybrid F1 and F2 progeny showing incomplete dominance in Snapdragon and co-dominance in human blood group be different from Mendelian monohybrid F1 and F2 progeny? Explain.

                                                OR


Explain the process of transcription in Eukaryotes.


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Q25 :

Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.
(a) What is a vaccine? Explain how does it impart immunity to the child against the disease.
(b) With the help of an example each, differentiate between active and passive immunity.
 

OR

What are biofertilizers? Describe their role in agriculture. Why are they preferred to chemical fertilizers?


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Q26 :

(a) Explain the events after pollination leading to the formation of a seed in angiosperms.
(b) Mention the ploidy levels of the cells of different parts of an albuminous seed.


OR

Explain the process of fertilisation and implantation in humans.


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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.