Board Paper of Class 12-Science 2010 Biology (SET 3) - Solutions
General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four Sections A, B, C and D. Section A contains 8 questions of one mark each, Section B is of 10 questions of two marks each, Section C is of 9 questions of three marks each and Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
- Question 1
Mention
one positive and one negative application of amniocentesis.
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- Question 2
How do
animals like fish and snails avoid summer related unfavourable
conditions?
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- Question 3
In a pond
there were 200 frogs. 40 more were born in a year. Calculate the
birth rate of the population.
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- Question 5
Name a
molecular diagnostic technique to detect the presence of a pathogen
in its early stage of infection.
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- Question 6
Name the
scientist who disproved spontaneous generation theory.
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- Question 7
What is it
that prevents a child to suffer from a disease he/she is vaccinated
against? Give one reason.
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- Question 8
Why is the
enzyme cellulose used for isolating genetic material from plant cells
but not for animal cells?
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- Question 9
Where does
triple fusion take place in a flowering plant? Why is it so called?
Mention its significance.
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- Question 10
Why
certain regions have declared as biodiversity “hot spots”
by environmentalists of the world? Name any two “hot spot”
regions of India.
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- Question 11
A moss
plant produces a large number of antherozoids but relatively only a
few egg cells. Why?
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- Question 12
Why is the
introduction of genetically engineered lymphocytes into a ADA
deficiency patient not a permanent cure? Suggest a possible permanent
cure.
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- Question 13
Study the
given food chain and answer the questions that follow:
(i) Give
reasons why there is a continuous increase in the DDT content in
different trophic levels of the chain.
(ii) Name
the phenomenon responsible for the increase in DDT content.
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- Question 14
Honey
collection improves when beehives are kept in crop-fields during
flowering season. Explain.
OR
How does
addition of a small amount of curd to fresh milk help formation of
curd? Mention a nutritional quality that gets added to the curd.
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- Question 15
Name the
type of food chains responsible for the flow of larger fraction of
energy in an aquatic and a terrestrial ecosystem respectively.
Mention one difference between the two food chains.
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- Question 16
Name the
host and the site where the following occur in the life-cycle of a
malarial parasite:
(a)
Formation of gametocytes
(b) Fusion
of gametocytes
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- Question 17
Why are F2
phenotypic and genotypic ratios same in a cross between red-flowered
snapdragon and white-flowered snapdragon plants. Explain with the
help of a cross.
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- Question 18
How does
the floral pattern of Mediterranean orchid Ophrys guarantee
cross pollination?
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- Question 19
During his
studies on genes in Drosophila that were sex-linked T.H.
Morgan found F2 − population phenotypic ratios
deviated from expected 9:3:3:1. Explain the conclusion he arrived at.
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- Question 20
Describe the termination process of transcription in bacteria.
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- Question 21
How does
RNA interference help in developing resistance in tobacco plant
against nematode infection?
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- Question 22
Draw a
longitudinal section of a post − pollinated Pistil showing
entry of pollen tube into a mature embryo-sac. Label filiform
apparatus, chalazal end, Hilum, antipodals, male gametes and
secondary nucleus.
OR
Draw a
labelled sectional view of seminiferous tubule of a human male.
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- Question 23
Explain
the efforts which must be put in to improve health, hygiene and milk
yield of cattle in a dairy farm.
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- Question 24
Explain
convergent and divergent evolution with the help of one example of
each.
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- Question 25
Eco RI is
used cut a segment of foreign DNA and that of a vector DNA to form a
recombinant DNA. Show with the help of schematic diagrams.
(i)The
set of palindronic nucleotide sequence of base pairs the Eco RI will
recognise in both the DNA segments. Mark the site at which Eco RI
will act and cut both the segments.
(ii)Sticky ends formed on both the segments where the two DNA
segments will join later to form a recombinant DNA.
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- Question 26
An
antibody molecule is represented as H2L2.
Explain.
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- Question 27
Identify
a, b, c, d, e and f in the table given below:
|
Organism
|
Bioactive molecule
|
Use
|
1.
|
Monascus perpureus
(Yeast)
|
|
|
2.
|
|
|
Antibiotic
|
3.
|
|
Cyclosporin A
|
|
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- Question 28
When and where are primary oocytes formed in a human female? Trace the development of these oocytes till ovulation (in menstrual cycle). How do gonadotropins influence this developmental process?
OR
(a)Explain the events taking place at the time of fertilization of an ovum in a human female.
(b)Trace the development of zygote upto its implantation in the uterus.
(c)Name and draw a labelled sectional view of the embryonic stage that gets implanted.
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- Question 29
Draw and
explain a logistic curve for a population of density (N) at time (t)
whose intrinsic rate of natural increase is (r) and carrying capacity
is (k).
OR
Describe
the process of decomposition of detritus under the following heads:
Fragmentation; leaching; catabolism; humification and mineralization.
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- Question 30
Write the
symptoms of haemophilia and sickle-cell anaemia in humans.
Explain
how the inheritance pattern of the two diseases differ from each
other.
OR
(a) Write
Hardy-Weinberg principle.
(b)
Explain the three different ways the natural selection can affect the
frequency of a heritable trait in a population shown in the graph
given below.
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