12th Biology Paper Solutions Set 1 : 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 :

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


Answer :

Drones of honey bees are haploid and possess 16 chromosomes.
Drones of honey bees donate 16 chromosomes (one pair) to the progeny; thus, mitosis is the cell division that is involved in the production of sperms by drones.

Q2 :

What is a cistron?


Answer :

Cistron is a section of gene that codes for a certain polypeptide or protein.

Q3 :

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.

Q4 :

Why do children cured by enzyme-replacement therapy for adenosine deaminase deficiency need periodic treatment?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q5 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q6 :

Why do moss plants produce very large number of male gametes? Provide one reason. What are these gametes called?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q7 :

Select the homologous structures from the combinations given below :
(i) Forelimbs of whales and bats
(ii) Tuber of potato and sweet potato
(iii) Eyes of octopus and mammals
(iv) Thorns of Bougainvillea and tendrils of Cucurbita
(b) State the kind of evolution they represent.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q8 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q9 :

Explain the different steps involved during primary treatment phase of sewage.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q10 :

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.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q11 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q12 :

During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Work out a cross to show how it it possible.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q13 :

Explain the significance of satellite DNA in DNA fingerprinting technique.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q14 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q15 :

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.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q16 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q17 :

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 ?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q18 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q19 :

Describe any three potential applications of genetically modified plants.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q20 :

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


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q21 :

How do snails, seeds, bears, zooplanktons, fungi and bacteria adapt to conditions unfavourable for their survival?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q22 :

With the help of a flow chart, show the phenomenon of biomagnification of DDT in an aquatic food chain.


Answer :

Please Register/Login to get access to all solutions Facebook Login
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.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q24 :

(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.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q25 :

(a) Why are thalassemia and haemophilia categorized as Mendelian disorders ? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.

(b) Write the genotypes of the normal parents producing a haemophilic son.

OR

How do m-RNA, t-RNA and ribosomes help in the process of translation ?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q26 :

(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.


Answer :

Please Register/Login to get access to all solutions Facebook Login

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.