BHARATIYA VIDYA BHAVAN, KOCHI
FIRST MODEL EXAMINATION
2023-2024
Std : XII BIOLOGY( 044) Max. Marks:70
Time: 3hrs
SET -1
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.
SECTION A
Q no Question Mark
1 1
Figure (i) and Figure (ii) given below are showing two stages of megasporogenesis in a
typical angiosperm plant.Choose the option showing the correct ploidy of X,Y and Z in the
table given below.
X Y Z
(a) 2n n 2n
(b) 2n n n
(c) n 2n 3n
(d) n 3n 2n
1
2 1
Select the correct statements with respect to the development of endosperm in a typical
angiosperm plant.
(i) Embryo development precedes endosperm development.
(ii) Endosperm cells divide repeatedly to form a triploid endosperm.
(iii) Endosperm tissue has scanty reserves of food materials.
(iv) PEN undergoes successive divisions to form a free nuclear endosperm.
3
1
AUG on m RNA will result in the activation of which of the following RNA having correct
combination of amino acids:
A B
(a) UAC Methionine
(b) Methionine UAC
(c) Methionine AUG
(d) AUG Methionine.
1
4 Which of the following combination of chromosome numbers represents the correct 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
1
5 25 individuals in a population are homozygous dominant, then the individuals that are
expected to be homozygous recessive are
(a) 100
(b) 75
(c) 50
(d) 25
2
6 Appearance of antibiotic-resistant bacteria is an example of 1
(a) adaptive radiation
(b) transduction
(c) pre-existing variation in the population
(d)divergent evolution.
7 1
Colour blindness is a sex linked recessive trait in humans. A man with normal colour
vision marries a woman, who is color blind. What would be the possible genotypes of the
parents, the son and the daughter of this couple?
Mother Father Daughter Son
(a) XX Xٰ² CY XXC Xy
(b) XCXC XCY XCXC XY
(c ) XXC XY XXC XY
(d) XCXC XY XXC XCY
1
8 The trait shown in the pedigree chart below is :
(a) Autosomal recessive
(b) Sex linked recessive
(c) Autosomal dominant
(d) Sex linked dominant
1
9 Patients having a high cholesterol level in blood is administered by giving drugs that
inhibit the enzyme responsible for synthesis of cholesterol. This would be
(a) Statins produced from Trichoderma polysporum
(b) Cyclosporin A produced from Trichoderma polysporum
(c) Statins produced from Monascus purpureus
(d) Streptokinase produced from Streptococcus
3
1
10 The given schematic illustration shows three steps A, B and C of the polymerase chain
reaction.
Which of the following statements are correct with reference to the illustration given
above?
(i) Step A is showing denaturation at low temperature.
(ii) Step B is the denaturation of a DNA strand at high temperature followed by annealing .
(iii) Step C is an extension of DNA in presence of thermostable DNA polymerase.
(iv) Step B is an extension with two sets of primers.
(a) (i) and (iii) only
(b) (ii) and (iii) only
(c) (ii) only
(d) (i) only
1
11 Bt toxin kill the larvae of certain insects
(a) By binding the activated toxin on midgut epithelial cells, creating pores, leading to
swelling and lysis
(b) By stopping of transcription of larval cells
(c) By altering central dogma taking place in the cells of gut of larva
(d) By stopping protein synthesis.
12 1
If we completely remove the decomposers from an ecosystem, their functioning will be
adversely affected because
(a) Herbivores will not receive solar energy
(b) Energy flow will be blocked
(c) The rate of decomposition will be very high
(d) Mineral movement will be blocked
4
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: Cleistogamous flowers have assured seed-set 1
Reason: Cleistogamous flowers are invariably autogamous and do not depend on
any pollinating agent
14 Assertion: DNA fingerprinting has an important application in paternity testing in case 1
of dispute.
Reason: DNA fingerprinting employs polymorphism in the DNA sequences as the
basis and such polymorphisms are invariable.
15 Assertion: Cannabinoids are drugs of abuse 1
Reason: They affect the cardio vascular system and central nervous system.
16 Assertion: Special methods are necessary to incorporate the alien or recombinant DNA 1
into the host cell.
Reason : DNA is a hydrophobic molecule.
SECTION - B
List the different parts of human oviduct through which the ovum travels till it meets the
17 sperm for fertilization. 2
(a) Write the genotypes of:
18 (i) an individual who is a carrier of sickle cell anaemia gene, but apparently unaffected 2
and
(ii) an individual affected with the disease.
(b) Why do normal blood cells become elongated sickle-shaped structure in a
person suffering from sickle -cell anaemia?
2
19
Interpret the above given graph in terms of innate and acquired immunity
5
20 (a) Identify and name the structures A and B marked in the image given below. 2
(b) State their importance in various biotechnology experiments.
21 What type of ecological pyramid would be obtained with the following data? Construct the same 2
using the data given below:
Secondary consumer - 120 kg/m2
Primary consumer - 60 kg/m2
Primary producer - 10 kg/m2
OR
Given below is a diagrammatic representation of energy flow through different trophic
levels in an ecosystem.
Give a reason for :
(a) The difference found between NPP and GPP at each trophic levels.
(b) The number of trophic levels in the GFC is restricted.
6
SECTION C
22 3
(a) Label A and C. Write down the chromosome number in each cell.
(b) The factors released from F on stimulation by a gonadotropin helps in an
important process. Identify the hormone and name the process.
23 The events of the menstrual cycle are represented below. Answer the following questions. 3
(i) State the levels of FSH, LH and simply by mentioning high or low around 13th and 14th
day and 21st to 23rd day.
(ii) In which of the above-mentioned phases does egg travel to fallopian tube?
(iii) Why there is no menstruation after fertilization?
24 (a) Name a chromosomal disorder in human caused due to 3
(i)gain of an autosome and
(ii)loss of sex chromosome in females.
(b) Explain the cause in a human to have sex chromosomes as XXY instead of XX or XY.
(c ) List any two ways such individuals are different from the normal being.
7
A population of black and white shelled snails reside in a snowy area. There is a predator
25 3
bird which preys on both black shelled and and white shelled snails. Identify and reason
out the mode of operational technique of natural selection found in the given figure C.
Give a graphical representation of the same.
A B C
26 Study the diagram of STP given below and answer the following questions: 3
(a) Which one of the two STPs (A) or (B) will be more effective in treating human
excreta in the municipal waste? Why?
(b) Write the steps followed in carrying the treatment of the sewage in step (Z), till it is
passed on to the “anaerobic sludge digesters”.
(a) Write the scientific name of the nematode that infects the tobacco plants and
27 thepart that it infects. 3
(b) How is agrobacterium used to protect tobacco plants from this attack?
OR
Two children ,A and B aged 4 and 5 years respectively visited a hospital with a similar
genetic disorder .The girl A was provided enzyme replacement therapy and was advised to
revisit periodically for further treatment.The girl B was, however, given a therapy that did
not require revisit for further treatment.
(a) Name the ailments the two girls were suffering from?
(b) Why did the treatment provided to girl A require repeated visits?
(c) How was girl B cured permanently?
8
28 The following graph shows the species -area relationship. Answer the following questions as
directed. 3
(a) Name the naturalist who studied the kind of relationship shown in the graph. Write the
observations made by him.
(b) Write the situation as discovered by the ecologists when the value of 'Z' (slope of the line) lies
between 0.6 and 1.2. What does 'Z' stand for?
(c) When would the slope of the line 'b' become steeper?
SECTION D
29 Rakesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch 4
of the observations of the experiment performed by him
(a) At which end he would have loaded the samples and where ?
OR
Analyze the reason for different positions taken up by the DNA bands.
(b) What is elution?
(c) Elaborate the step he would have followed to visualize DNA bands?
9
30 In laboratory experiments, two species of paramecium were grown alone and in the 4
presence of the other species. The following graphs show the growth of species 1 and
species 2, both alone and when in mixed culture.
(a) Which species of the two is more affected by interspecific competition? Why?
(b) Give two examples where inter specific competition enables the superior ones to
survive.
(c) State Gause’s competitive exclusion principle. Under which condition is this true?
OR
From the graph what does E stand for?
Briefly explain what slope C and curve D indicates .
10
5
SECTION E
31
(a) Identify A and B. How do they prevent conception?
(b) Why removal of gonads is not considered to be a contraceptive action?
(c) STDs are a threat to reproductive health. Write down any two complications that
STDs lead to. Name any two such diseases which cannot be cured.
OR
(a) Amniocentesis for sex determination is banned in our country. Is this ban
necessary? Comment.
(b) Give the scientific name of the ART programme where in-vitro fertilization is done
and briefly explain the same.
(c) Given below are some contraceptives used. Write down their use and mode of
action.
Name of contraceptive Requirement of Mode of action
device/Method contraceptive for
i. Oral pill
ii. Cervical vaults
iii. Tubectomy
32 ATGGAGTACTTCGTGTGA is the coding strand of DNA in a transcription unit. 5
(a) Write the mRNA transcribed from this DNA segment,along with its polarity.
(b) How many aminoacids does it code for ? Why?
(c) Why are some untranslated sequences of bases seen in mRNA coding for a
polypeptide? Where exactly are they present on mRNA?
OR
(a)A garden pea plant bearing terminal ,violet flowers ,when crossed with another pea
plant bearing axial violet flowers produced axial violet flowers and axial white flowers
in the ratio 3:1 .Workout a cross showing the genotypes of the parent pea plants and
their progeny.
(b) Name and state the law that can be derived from this cross and not from a monohybrid
cross.
11
33 Trace the life cycle of Plasmodium in humans from the stage of entry until it is picked up 5
by the female Anopheles.
OR
i) How do antibiotics work?
ii) Write down the consequences that would result from inappropriate usage of
antibiotics.
iii) Name - a) The pathogen of Dengue fever b) Mode of transmission of
Chikungunya
iv) Dengue fever in some cases turns out to be a lifethreatening disease. Give
reason.
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