KendriyaVidyalayaSangathan
JAIPUR REGION
Class – XII 2023-2024 Sub: Biology
M.M: 70 Time: 3 hrs.
General Instructions:
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions. All questions are compulsory.
(iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks
each;Section– C has 7 questions of 3 marks each; Section– D has 2 case-based questions
of 4 marks each; and Section–E has 3 questions of 5 marks each.
(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.
Q.NO. SECTION A MARK
S
1. Which of the following seeds have remained alive for the longest period? 1
a) Phoenix dactylifera
b) Mangiferaindica
c) Strigaasiatica
d) Yucca gigantean
2. Which of the following combination of chromosome numbers represents the correct 1
sex determination pattern in honey bees?
a) Male 32. female 16
b) Male 16, female 32
c) Male 31, female 32
d) Female 32, male 31
3. Total number of nucleotide sequences of DNA that codes for a hormone is 1530. The 1
proportion of different bases in the sequence is found to be adenine= 34%, guanine=
19%, cytosine =23%, thymine = 19%.Applying Chargaff's rule , what conclusion can
be drawn ?
a) It is a single stranded DNA.
b) It is a single stranded DNA coiled on histones.
c) It is a double stranded circular DNA.
d) It is a double stranded linear DNA.
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4. Which of the following is an example for link species? 1
a)Lobe fish
b) Dodo bird
c)Sea weed
d)Chimpanzee
5. A protoxin is : 1
a) a primitive toxin
b) a denatured toxin
c) toxin produced by protozoa
d) inactive toxin
6. The status of the human population reflected in the human age pyramid given below 1
is :
a)Declining population
b)Stable population
c) Expanding population
d)Extinct population
7. An inverted pyramid of biomass can be found in which ecosystem? 1
a) Forest
b) Marine
c) Grass land
d) Tundra
8. The decrease in the T lymhocytes count in human blood will result in 1
a) decrease in antigens
b) decrease in antibodies
c) increase in antigens
d) increase in antibodies
9 Which one of the following is not a major characteristic feature of biodiversity hot 1
spots?
a) Abundance of endemic species
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b) Large number of species
c) Mostly located in the polar regions.
d) Mostly located in the tropics
10 Which of the following is not a characteristic of the plasmids? 1
a) Single-stranded
b) Circular DNA
c) Independent replication
d) Extranuclear
11 A probe which is a molecule used to locate homologous sequences in a mixture of 1
DNA or RNA molecules could be:
a) a ssDNA
b) can be ssDNA but not ssRNA
c) a RNA
d) either RNA or DNA.
12 The active chemical drug reserpine is obtained from: 1
a) Rauwolfia
b) Algae
c) Dhatura
d)Cannabis
Question No. 13 to 16 consist of two statements – Assertion (A) and Reason (R).
Answer these questions selecting the appropriate option given below:
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true and R is not the correct explanation of A.
c) A is true but R is false.
d) A is False but R is true.
13 Assertion: Synthetic oligonucleotide polymers are used during Annealing in a PCR. 1
Reason: The primers bind to the double stranded DNA at their complimentary
regions.
14 Assertion: RNA polymerases are able to catalyse all three steps of translation. 1
Reason: RNA polymerases contain an initiation factor and a termination factor in
them .
15 Assertion: Sickle-cell anaemia is an autosome-linked recessive disorder. 1
Reason: It appears only in human male which can be transferred to their grandson
through carrier daughter.
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16 Assertion: Endosperm is completely consumed during, the development of embryo in 1
ex albuminous seeds.
Reason: Pea and beans are all examples of ex-albuminous seeds.
SECTION B
17. With the help of a Punnett square, find the percentage of heterozygous individuals in 2
a F2 population in a cross involving a true breeding pea plant with green pods and a
true breeding pea plant with yellow pods respectively.
18. List the two types of immunity a human body. Explain the differences between the two 2
types.
19. Explain the two factors responsible for conferring stability to double helix structure of 2
DNA.
20. a) Give an example of viral bio-control agent. 2
b) Why are they considered to be desirable when an ecologically sensitive area is
being treated?
21. a) When prickly pear cactus was introduced into Australia in early 1920s, it caused 2
havoc and ecosystem instability by achieving very high population densities. Explain
the reason for its rapid spread into millions of hectares of rangeland.
b) State the importance of Prey-predator relationship in a habitat.
OR
The Evil Quartet explains the accelerated rate of species extinction world wide.
Describe any two of them with suitable examples.
SECTION C
22. a) Draw a sectional view of seminiferous tubule of a human. Label the following cells 2+1=3
in the seminiferous tubule:
i) Cells that divide by mitosis to increase their number.
ii) Cells that undergo Meiosis I
iii) Cells that undergo Meiosis II.
iv) Cells that help in the process of spermiogenesis.
b) Mention the role of Leydig cells.
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23. What is Down's syndrome? Give its symptoms and cause. 3
24. Write the events that take place when a vaccine for any disease is introduced into 3
the human body.
25. a) Write the characteristic features of anther, pollen and stigma of wind-pollinated 3
flowers.
b) How do flowers reward their insect pollinators? Explain.
26. a) Identify the polarity from a to a' in the given diagram and mention how many more 1+1+1
amino acids are expected to be added to this polypeptide chain. =3
b) Mention the DNA sequence coding for valine and the codon for the same amino
acid.
c) Why are some untranslated sequence of bases seen in mRNA coding for a
polypeptide? Where exactly are they present on mRNA?
27. List the three molecular diagnostic techniques that help detect pathogens from 3
suspected patients. Mention one advantage of these techniques over conventional
methods.
OR
Explain briefly the following:
a) Bioreactor
b) Bt cotton
c) Cloning of Gene
28. Expand and explain the following techniques used in the "Test Tube Baby" 1+1+1
programme: =3
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a) GIFT
b) ZIFT
c) IUI
SECTION D
29. Tobacco is a silent killer in our midst that kills an estimated 1.35 million indians every 1+1+1
year. According to Global Youth Tobacco Survey, India has the second largest +1=4
number of tobacco smokers in the world and of this 13 lakh die evervvear from
tobacco related diseases. 8.5% of school going children in the age group 13 -15 years
use tobacco in some form in India. Tobacco is known to be a major risk factor for
several non- communicable diseases such as cancer, cardio vascular disease,
diabetes and chronic lung diseases. Nearly 2.7% of all cancers in India are due to
tobacco usage.
Answer the following questions based on the above case study-
a) Name the alkaloid in tobacco that is responsible for its harmful effects.
b)What are the likely reasons for more children getting into the habit of smoking?
c) How does smoking bring about oxygen deficiency in the blood?
OR
c) Explain how the use of tobacco increases the blood pressure?
30. Read the following regarding population interaction and answer the questions that 1+1+1
follow: +1=4
An ecological community consist of all the populations of all the different species that
live together in a particular area. Interactions between different species in a
communityare called interspecific interactions. Different type of interspecific
interaction havedifferent effects on two participant which may be
positive(+),negative(-) or neutral(0).The main type of interspecific interactions include
: Competition, Predation, Mutualism, Commensalism and Parasitism.
In most case, many species share a habitat and the interaction between them play a
major role in regulating population growth and abundance.
a) Name the interaction where one species is benefitted while other is not affected.
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b) Give an example of mutualism.
c) Explain the kind of interaction built by cuscuta growing on hedge plant.
d) The Abingdon tortoise in Galapagos Islands became extinct within a decade after
goats were introduced on the island. Explain the cause for this effect.
OR
Explain Mac Arthur “Resource Partitioning” theory of competition.
SECTION E
31. Give reasons why : 1+1+1
a) most zygotes in angiosperms divide only after certain amount of endosperm is +1+1=
formed. 5
b)which is exalbuminous or albuminous- groundnut or castor and why.
c) micropyle remains as a small pore in the seed coat of a seed.
d) integuments of an ovule harden and the water content is highly reduced, as the
seed matures.
e) apple and cashew are not called true fruits.
OR
Given alongside is the diagram of a human ovum surrounded by a few sperms.
Observe the diagram and answer the following questions:
a) Compare the fate of sperms shown in the diagram.
b) What is the role of zonapellucida in this process?
c) Analyze the changes occurring in the ovum during the process.
d) Mention what helps in the entry of sperm into the ovum.
e) Specify the region of female reproductive system where the event represented in
the diagram takes place.
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32. a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues 3+2=5
worked with for their experiments. Explain the correlation between linkage and
recombination with respect to genes as studied by them.3
b) How did Sturtevant explain gene mapping while working with Morgan? 2
OR
a) Write the specific features of the genetic code AUG. 1
b) Genetic codes can be universal and degenerate. Write about them, giving one
example of each . 2
c) Explain aminoacylation of the tRNA. 2
33. Answer the following question with respect to recombinant DNA technology: 2+2=1
a) Why is plasmid considered to be an important tool in rDNA technology? From =5
where can plasmids be isolated? (Any two sources)
b) Explain the role of 'ori' and 'selectable marker' in a cloning vector.
c) "r-DNA technology cannot proceed without restriction endonuclease." Justify.
OR
a) Name the source from which insulin was extracted earlier. Why is this insulin no
more in use by diabetic people?
b) Explain the process of synthesis of insulin by Eli Lilly Company. Name the
technique used by the company.
c) How is the insulin produced by human body different from the insulin produced by
the above mentioned company?
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