Pre-Board Examination 2021-22
Grade 12 MM -35
Subject: Biology Time: 2Hrs
General Instructions:
i) All questions are compulsory.
ii) The question paper has three sections and 13 questions. All questions are
compulsory.
iii) Section–A has 6 questions of 2 marks each; Section–B has 6 questions of 3 marks
each; and Section–C has a case-based question of 5 marks.
iv) There is no overall choice. However, internal choices have been provided in
some questions. A student has to attempt only one of the alternatives in such
questions.
v) Wherever necessary, neat and properly labeled diagrams should be drawn.
Section A
1. Tobacco plants are damaged severely when infested with Meloidegyne incognitia . Name and explain
the strategy that is adopted to stop this infestation.
2. How has recombinant technology helped in large scale production of vaccines? Explain giving one
example.
OR
Write short notes on the Production of human insulin hormone by E. coli.
3. Identify the curves 'a' and 'b' shown in the graph given below.
4. Identify the compound chemical structure is shown below. State any three of its effects organism’s
body.
5. How does one visualize DNA on an agarose gel ?
6. How will you measure population density in case of fish in lake, tiger census in national park and
parthenium grass?
OR
The figure given below represents a molecule present in the body of a mammal
a) Name the parts labelled ‘a’ and ‘b’ in the molecule shown above.
b) Name the type of cells that produce this molecule.
Section B
7. Explain the different steps involved in the secondary treatment of sewage.
OR
Microbes can be used to decrease the use of chemical fertilizers. Explain how this can be
accomplished.
8. The Indian Government refuted the attempt by a multinational company (MNC) to patent the
antiseptic property of curcumin derived from Turmeric. Analyze the unethical practice adopted
by the MNC, state its implications and suggest provisions in the Indian Law to prevent such
malpractices.
9. Your classmate complains of headache and cough. The doctor confirms that he is suffering from
Pneumonia and not common cold, on the basis of certain symptoms. List these symptoms. Mention
any two precautions to be followed to prevent the spread of this disease.
10. The graph given below shows the distribution of biomes:
a) What do the ‘X’ and ‘Y’ axes represent?
b) Identify the ‘grassland’ and ‘coniferous forest’ biomes, from the above figure.
c) Why is ‘F’ located at the given position in the graph?
11. Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of the
observations of the experiment performed by him.
(a) At which end he would have loaded the samples and where?
(b) Analyse the reason for different positions taken up by the DNA bands.
(c) Elaborate the step he would have followed to visualize DNA bands.
12. Do you consider passive smoking is more dangerous than active smoking? Why?
Section C
The organism has various alterations for coping with extremes environment. Some able to respond through
certain physiological adjustments while others do so behaviorally. These responses are their adaptations.
Many adaptations have evolved over a long evolutionary time and are genetically fixed. Many desert plants
have thick cuticle on their leaf surfaces and have their stomata arranged in deep pits to minimize water loss
through transpiration. In the polar seas, aquatic mammals like seals have a thick layer of fat or blubber below
their skin that act as an insulator and reduce the loss of body heat. Some organisms possess adaptations that
are physiological which allows them to respond quickly to a stressful situation.
1. State Allen’s rule
2. In the absence of external source of water, how the Kangaroo rat in North American desert is capable
of meeting all its water requirements?
3. Write the advantages of spine like leaves in opuntia.
4. Write the adaptations of Desert lizard to cope with environmental stress.
OR
Large quantities of waste water are generated every day in cities and towns . A major components of this
waste water is human excreta. This Municipal waste water is also called sewage. It contains large amount of
organic matter and microbes. Treatment of waste water is done by the heterotrophic microbes naturally
present in the sewage. This treatment is carried out in two stages : Primary treatment which basically
involves the physical removal of particles large and small from the sewage and secondary treatment or
Biological treatment. The primary effluent is passed into large aeration tanks where it was constantly agitated
mechanically and the air is pumped into it. While growing these microbes consume the major part of the
organic matter in the effluent. This significantly reduce the BOD(Biochemical Oxygen Demand ) of the
effluent.
1. How does BOD form an index of water pollution?
2. Differentiate between primary and secondary treatment.
3. Define activated sludge.
4. In which way can sewage be harmful to us.
