12th Biology Paper Solutions Set 2 : CBSE All India 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 :

List two advantages of the use of unleaded petrol in automobiles as fuel.


Answer :

Following are the two advantages of using unleaded petrol as fuel in automobiles:

  • Unleaded petrol does not release lead compounds from exhaust fumes into the atmosphere and causes less pollution.
  • As unleaded petrol does not emit harmful compounds, it helps in preventing health diseases like bronchitis, asthma and lung diseases.

Q2 :

Retroviruses have no DNA. However, the DNA of the infected host cell does possess viral DNA. How is it possible?


Answer :

After attacking the host cell, retrovirus enters into macrophages (as in case of HIV) where RNA genome of the virus replicates to form viral DNA using reverse transcriptase enzyme. This viral DNA gets incorporated into the host's cell DNA and directs the infected cells to produce more viruses. Hence, the infected host cell possesses viral DNA.

Q3 :

State the cause of adenosine deaminase enzyme deficiency.


Answer :

Adenosine deaminase (ADA) enzyme deficiency is caused due to the mutation in the gene encoding it and this gene is present on chromosome number 20.
ADA deficiency is inherited as an autosomal recessive trait.

Q4 :

What is a cistron?


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Q5 :

How many chromosomes do drones of honeybee possess? Name the type of cell division involved in the production of sperms by them.


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Q6 :

What is mutualism? Mention any two examples where the organisms involved are commercially exploited in agriculture.


OR

List any four techniques where the principle of ex-situ conservation of biodiversity has been employed.


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Q7 :

(a) Why are the plants raised through micropropagation termed as somaclones ?
(b) Mention two advantages of this technique.


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Q8 :

Explain the process of secondary treatment  given to the primary effluent up to the point it shows significant change in the level of biological oxygen demand (BOD) in it.


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Q9 :

(a) Select the analogous structures from the combinations given below :

(i) Forelimbs of whales and bats

(ii) Eyes of octopus and mammals

(iii) Tuber of sweet potato and potato

(iv) Thorns of Bougainvillea and tendrils of Cucurbita

(b) State the kind of evolution they represent.


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Q10 :

A moss plant is unable to complete its life-cycle in a dry environment. State two reasons.


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Q11 :

A heavily bleeding and bruised road accident victim was brought to a nursing home. The doctor immediately gave him an injection to protect him against a deadly disease.
(a) Write what did the doctor inject into the patient's body.
(b) How do you think this injection would protect the patient against the disease?
(c) Name the disease against which this injection was given and the kind of immunity it provides.


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Q12 :

Explain the significance of satellite DNA in DNA fingerprinting technique.


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Q13 :

What does the following equation represent? Explain
p2 + 2 pq + q2 = 1


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Q14 :

Two independent monohybrid crosses were carried out involving a tall pea plant with a dwarf pea plant. In the first cross, the offspring population had equal number of tall and dwarf plants, whereas in the second cross it was different. Work out the crosses, and explain giving reasons for the difference in the offspring populations.


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Q15 :

State what is apomixis. Comment on its significance. How can it be commercially used?


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Q16 :

State the medicinal value and the bioactive molecules produced by Streptococcus, Monascus and Trichoderma.


OR

What are methanogens ? How do they help to generate biogas ?


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Q17 :

Describe any three potential applications of genetically modified plants.


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Q18 :

How did an American Company. Eli Lilly use the knowledge of r-DNA technology to produce human insulin?


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Q19 :

Explain co-evolution with reference to parasites and their hosts. Mention any four special adaptive features evolved in parasites for their parasitic mode of life.


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Q20 :

Rearrange the following in the current sequences to accomplish an important biotechnological reaction :
(a) In vitro synthesis of region of DNA of interest
(b) Chemically synthesised oligonucleotides
(c) Enzyme DNA-polymerase
(d) Complementary region of DNA
(e) Genomic DNA template
(f) Nucleotides provided
(g) Primers
(h) Thermostable DNA-polymerase (from Thermus aquaticus)
(i) Denaturation of ds-DNA


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Q21 :

With the help of a flow-chart exhibit the events of eutrophication.


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Q22 :

Enumerate any six essentials of good, effective Dairy Farm Management Practices.


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Q23 :

Your school has been selected by the Department of Education to organize and host an interschool seminar on "Reproductive Health – Problems and Practices". However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is "too embarrassing."
Put forth four arguments with appropriate reasons and explanation to justify the topic to be very essential and timely.


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Q24 :

(a) List the different attributes that a population has and not an individual organism.

(b) What is population density ? Explain any three different ways the population density can be measured, with the help of an example each.

OR
 
"It is often said that the pyramid of energy is always upright. On the other hand, the pyramid of biomass can be both upright and inverted." Explain with the help of examples and sketches.


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Q25 :

(a) Plan an experiment and prepare a flow chart of the steps that you would follow to ensure that the seeds are formed only from the desired sets of pollen grains. Name the type of experiment that you carried out.

(b) Write the importance of such experiments.

OR

Describe the roles of pituitary and ovarian hormones during the menstrual cycle in a human female.


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Q26 :

(a) Why are colour blindness and thalassemia categorised as Mendelian disorders ? Write the symptoms of these diseases seen in people suffering from them.

(b) About 8% of human male population suffers from colour blindness whereas only about 0.4% of human female population suffers from this disease. Write an explanation to show how it is possible.

OR
 
Explain the process of transcription in prokaryotes. How is the process different in eukaryotes ?


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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.