Board Paper of Class 12-Science 2008 Biology (SET 1) - 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
Name any two vertebrate
body parts that are homologous to human forelimbs.
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- Question 2
When and
why do some animals like snails go into aestivation?
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- Question 4
What was
the speciality of the milk produced by the transgenic cow Rosie?
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- Question 5
How do neutrophils act
as a cellular barrier to pathogens in humans?
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- Question 6
Mention
the polarity of the DNA strands a-b and c-d shown in the replicating
fork given below.
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- Question 7
Mention
any two significant roles predation plays in nature.
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- Question 8
Why
is the polar region not a suitable habitat for tiny humming birds?
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- Question 9
(a) Expand IUD.
(b) Why is hormone releasing IUD considered a good contraceptive to space children?
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- Question 10
Name the
interaction in each of the following:
(a) Cuscuta
growing on a shoe flower plant
(b) Mycorrhiza
living on the roots of higher plants
(c) Clown
fish living among the tentacles of sea anemone
(d) Koel
laying her eggs in crow’s nest
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- Question 11
A
plant of Antirrhinum majus
with red flowers was crossed with another plant of the same species
with white flowers. The plants of the F1
generation bore pink flowers. Explain the pattern of inheritance with
the help of a cross.
OR
A woman
with blood group O married a man with AB group. Show the possible
blood groups of the progeny. List the alleles involved in this
inheritance.
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- Question 12
Why do
sportspersons often fall a victim to cocaine addiction?
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- Question 13
State the
difference between the first trophic level of detritus food chain and
grazing food chain.
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- Question 14
Coconut
palm is monoecious while date palm is dioecious. Why are they called
so?
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- Question 15
How
can DNA segments, separated by gel electrophoresis, be visualised
and isolated?
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- Question 16
How
do Darwin’s finches illustrate adaptive radiation?
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- Question 17
Name
the blank spaces a, b, c, and d from the
table given below:
-
Type of microbe
|
Scientific name
|
Commercial
product
|
Bacterium
|
a
|
Lactic acid
|
Fungus
|
b
|
Cyclosporine A
|
c
|
Monascus
purpureus
|
Statin
|
Fungus
|
Penicillium
notatum
|
d
|
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- Question 18
DDT
content in the water of a lake that supplies drinking water to the
nearby villages is found to be 0.003 ppm. The kingfishers of that
area are reported to have 3 ppm of DDT. Why has the concentration
increased in these birds? What harm will this cause to the bird
population? Name the phenomenon.
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- Question 19
(a)
Read the
graph given above and correlate the uterine events that take place
according to the hormonal levels on
(i) 6 −
15 days
(ii) 16 −
25 days
(iii) 26 −
28 days (if the ovum is not fertilised)
(b)
Specify the sources of the hormones mentioned in the graph.
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- Question 20
Explain
the role of baculoviruses as biological control agents. Mention their
importance in organic farming.
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- Question 21
(a) Draw the structure of the initiator tRNA adaptor molecule.
(b) Why is tRNA called an adaptor molecule?
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- Question 22
Study the
population growth curves shown above.
(i) Identify
curves ‘a’ and ‘b’.
(ii) Mention
the conditions responsible for the curves ‘a’ and ‘b’
respectively.
(iii) Give
the necessary equation of the curve ‘b’.
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- Question 23
Why
is Agrobacterium tumefaciens
a good cloning vector? Explain.
OR
Explain
the importance of (a) ori (b) ampR
and (c) rop in the E. coli
vector shown below:
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- Question 24
Study the mRNA segment given above which is complete to be translated into a polypeptide chain.
(i) Write the codons ‘a’ and ‘b’.
(ii) What do they code for?
(iii) How is peptide bond formed between two amino acids in the ribosome?
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- Question 25
(a) Name the infective stage of Plasmodium
which Anopheles
mosquito takes in along with the blood meal from an infected human.
(b) Why
does the infection cause fever in humans?
(c) Give a
flow chart of the part of the life-cycle of this parasite passed in
the insect.
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- Question 26
A factory
drains its waste water into the nearby lake. It has caused algal
bloom.
(a) How
was the algal bloom caused?
(b) What
would be the consequences?
(c) Name
the phenomenon that caused it.
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- Question 27
Study the given pedigree chart and answer the questions that follow.
(a) Is the trait recessive or dominant?
(b) Is the trait sex-linked or autosomal?
(c) Give the genotypes of the parents in generation I and of their third and fourth child in generation II.
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- Question 28
(a) Draw a
schematic labelled diagram of a fertilised embryo sac of an
Angiosperm.
(b)
Describe the stages in embryo development in a dicot plant.
OR
(a) Draw
a labelled diagram of a sectional view of human seminiferous tubule.
(b) Differentiate
between gametogenesis in human males and females on the basis of:
(i) Time of initiation of the process
(ii) Products formed at the end of the process
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- Question 29
Explain
the steps involved in the production of genetically engineered
insulin.
OR
(a) Name
the nematode that infests and damages tobacco roots.
(b) How
are transgenic tobacco plants produced to solve this problem?
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- Question 30
What
is ‘semi-conservative’ DNA replication? How was it
experimentally proved and by whom?
OR
A
homozygous tall pea plant with green seeds is crossed with a dwarf
pea plant with yellow seeds.
(i)
What would be the phenotype and genotype of F1?
(ii) Work out the phenotypic ratio of F2
generation with the help of a Punnett square.
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