12th Biology Paper Solutions Set 1 : CBSE Delhi 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 :

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.


Answer :

A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms with short life cycles for experiments because it enables the geneticist to study many generations of those organisms in their short lifespans.

Q2 :

Name the transcriptionally active region of chromatin in a nucleus.


Answer :

Euchromatin is the transcriptionally active region of chromatin in a nucleus.

Q3 :

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.


Answer :

Industrial melanism was the reason behind the increase in the population of dark-coloured moths along with the loss of lichens during industrialisation in England.
The tree trunks became darker (after industrialisation) with deposits of soot and smoke; hence, the number of dark moths increased as they were not easily visible to their predators while the white-winged ones were easily picked up by the predators. Thus, dark ones were selected by nature (natural selection) and light ones fail to survive.

Q4 :

Indiscrimate diagnostic practices using X-rays etc., should be avoided. Give one reason.


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Q5 :

What is Biopiracy ?


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Q6 :

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.


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Q7 :

Differentiate between male and female heterogamety.


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Q8 :

How has mutation breeding helped in improving the production of mung bean crop?


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Q9 :

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


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Q10 :

Many fresh water animals can not survive in marine environment. Explain.
 

OR

How are productivity, gross productivity, net primary productivity and secondary productivity interrelated ?


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Q11 :

Double fertilization is reported in plants of both, castor and groundnut. However, the mature seeds of groundnut are non-albuminous and castor are albuminous. Explain the post fertilization events that are responsible for it.


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Q12 :

Describe the process of Parturition in humans.


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Q13 :

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.


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Q14 :

(a) A DNA segment has a total of 1000 nucleotides, out of which 240 of them are adenine containing nucleotides. How many pyrimidine bases this DNA segment possesses?

(b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.


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Q15 :

Explain adaptive radiation with the help of a suitable example.


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Q16 :

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.


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Q17 :

Enlist the steps involved in inbreeding of cattle. Suggest two disadvantages of this practice.


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Q18 :

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.


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Q19 :

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.


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Q20 :

Draw a labelled sketch of sparged-stirred-tank bioreactor. Write its application.


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Q21 :

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.


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Q22 :

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.


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Q23 :

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.


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Q24 :

A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds.

Answer the following questions giving reasons :

(a) What is the minimum number of pollen grains that must have been involved in the pollination of its pistil?

(b) What would have been the minimum number of ovules present in the ovary?

(c) How many megaspore mother cells were involved?

(d) What is the minimum number of microspore mother cells involved in the above case?

(e) How many male gametes were involved in this case?

OR

During the reproductive cycle of a human female, when, where and how does a placenta develop? What is the function of placenta during pregnancy and embryo development?


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Q25 :

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?


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Q26 :

"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.


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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.