WHITEFIELD GLOBAL SCHOOL

PRE-BOARD 1 EXAMINATIONS 2024

GRADE XII
SUB:BIOLOGY

Time :3 hours Max. Marks: 70

Date: 13-12-24

General Instructions:

1. Allquestions are compulsory.

2. The question paper has five sections and 33 questions. Allquestions are compulsory.

3.Section-A has 16 questions of 1 mark each; Section--B has 5 questions of 2 marks each;
Section-Chas 7 questions of 3 marks each: Section–D has 2 case-based questions of 4
marks each; and SectionE has 3 questions of 5 marks each.
4. There is no overall choice. However, internal choices have been provided in some questions.
Astudent has to attempt only one of the alternatives in such questions.
5. Wherever necessary, neat and properly labeled diagrams should be drawn.

SECTIONA

Sl.No. Questions Content Marks

1 What is the main function of filiform apparatus present at the micropylar part of the ovule?

(a) It prevents the entry of more than one pollen tube into the embryo sac.

(b) It helps in the entry of pollen tube into an antipodal cell.

(c) It helps the pollen tube to enter the ovule through chalazal end. 1
(d)It guides the entry of pollen tube into a synergid and dischrge the male gametes.

2 Study the given figure and conclude the correct explanation from the options given below:

Sperm

-Cclls of the 1
corona radiata
Zone
Ovum
pellucida

Perivitcllinc space

(a) All the sperm attaches with ovum.

(b) Transport of sperm towards the ovum.
(c) Ovum and surrounded sperms were going to take part in fertilization.

(d Sperm induces changes in the cells of corona radiata and blocks the entry of
other additional sperms

1
 (a) Mutualism, parasitism, predation,commensalism
(aMutualism, parasitism, predation, ammensalism
(a) Mutualism, parasitism,
commensalism, predation
(a) Mutualism, predation, parasitism, commensalism

12. Which one of the following shows concept of speciesarea relationship? 1

(a) The number of species in an area increases with the size of the area.

(b) Larger species require larger habitat areas than do smaller species.
(c) Most species within any given area are endemic.
(d) The larger the area, the greaterthe extinction rate.

Read the question no. 13 to 16 of assertion and reason carefully to mark the correct optionout of the
options given below:
(a) if both the assertion and the reason
are true and the R is a correct explanation of the
assertion.
(b) Ifboth the assertion and reason
are true but the R is not a correct
(c) If the assertion is true explanation of the assertion.
but the reason is false.
(d) If both the
assertion and reason are
false.

13. Assertion :In a food chain, membersof

successive higher levels are fewerin number.
Reason :Number of organismsat 1
any trophic level depends upon
the availability of
organisms which serve as food at
the lower level.
A
14. Assertion : Insertion of recombinant DNA within the coding
sequence of b-galactosidase
Reason : results

Presence
in colourless
of insert
colonies.

results in inactivation of enzyme

b-galactosidaseknown as
insertional inactivation.

15.
Assertion: Species are groups of
potentially interbreedingnatural
populations which are
Reason :
isolated

Distinctive
from other such
groups.
morphological characters are
displayed due to reproductive isolation.
1

16. Assertion:The presently occurringspecies

extinction is from the
that have occurred
earlier.
different mass extinctions
Reason: Extinction present day
in is due to natural
causes,whereas
man-madecauses. earlier it was due to
A 1

SECTION B
17. Observe the population
growth curve and answer the
questions given below:

dN
(N)> at
K t
2
N{-): NeE
density
B
Population
Time (t)

4
 (c) 37.2 and 1.3% (d) 62.8% and 98.7%

symptoms, 1
7 A person is suffering from one disease and shows the following like sustained

headache and
high fever (39 to 40 degree Celsius), weakness, stomach
pain, constipation,

loss of appetite. His doctor confirmed that he is suffering from one bacterial infection. On
which of the following facts (given below) his doctor confirmed the bacterial infection.

()Salmonella typhi bacteria are responsible for the infection.

(ü) Streptococcuspneumonia is responsible for the infection.

(ii) By seeing the report which shows the positive result of Widal test.
through the bite of female Anopheles mosquito.
X
(iv) The pathogen is transmitted

fluid leading to severe problem in

(v) As a result of infection, the alveoli get filled with

respiration.

(aY(i) and (i) only (b)(i), (ii) and (v) only

c) (0), (ii), (iv) and (v) only (d) (0), (), (iv) and (v) only

of oil spills is a 1
8. A genetically engineered micro-organism used successfully in bioremediation

species of

Trichoderma (c) Xanthomonas (d) Bacillus

(a) Pseudomonas (b) x

1
9 ldentify the correct match of the technique with their role shown in the given figure.
Wells
DNA
bands
largest Smallcst

234

(a) Electrophoresis Differential migration of DNA fragments

(b)Column - Separation of chlorophyll chromatography pigments
(c) Gene cloning- Technique of obtaining identical copies of a particular DNA or a gene
segment
foreign genes into a host cell
(d) Microinjection -Technique of introducing

1
10. Cry llAb and cryIAC produce toxins that control

(a) cotton bollworms and corn borer respectively.

(b cotton borer and cotton bollworms respectively.
(c) tobacco budworms and nematodes respectively.

(d) nematodes and tobacco budworms respectively.

population interaction between species A and B are

11. Given below is a table depicting

Specics A Species B Name of Interaction

A?
1
B?
C?
D?

3
 each option
pair of evolutionary
concepts and examples provided in
3. ldentify the incorrect
whales, bats, cheethah and
human
(a) Divergent evolution - Forelimbs of

Convergent evolution - Flippers of penguin and dolphins

(b)

(c) Homologous structures - Vertebrate hearts

and Cucurbita
-Thorns and tendrils of Bougainvillea
(d) Analogous structures

The police bring you a sample 1

and you are asked to help solve

it.
4. Amurder has occurred,
is the killer's DNA and ask you for a chemical
from the crime scene of what they believe
thymine, ribose and
sample reveals the presence of adenine,
analysis. Your study of this

uracil, leading you to conclude that the sample is

(a) Pure DNA

(b) Pure RNA
(c) Probably a mixture of DNA and RNA
(d) Probably a mixture of rRNA and mRNA

1
5. Identify the correct function(s) of pills

(0) Inhibit ovulation and implantation.

(ü) Alter the quality of cervical mucus to prevent or retard the entry of sperms.
(i) Prevent the ejaculated semen from entering the female vagina.
(iv) Inhibit spermatogenesis.

(a) (i), ()and (ii) (b) (i) and (ii) (c) (0), (ii) and (iv) (d) (ii) and (iv)

6. The experiment shown in the given figure has been carried out by Morgan to show the 1

phenomenon of linkage and recombination. If in cross genes are tightly linked and in cross
I,
Il, genes are loosely linked then what will be the percentage of recombinants produced in

cross and cross Il respectively?

I
Cross I

y w
Parenal
Yellow wie Wild type

F, generation
y
Vild
w
pe Yellow,whie

Cross II

Parental
m m

Whte- inanre Wild ype

1V

F,generation
m
Wild tyye Whate. Iunntue

(a) 98.7% and 62.8% (b)1.3% and 37.2%

2
 pavhe

(a) ldentify A to D and write the function proper

(b)Explain how the hormones regulate the formation of mature gamete in human
female.

25. The-below diagram shows a typical biogas plant. Answer the following questions.

-Gb)

-Rigestos

(a) ldentify a, b and c.

(b) Explain how activated sludge used to generate biogas?

3

26. Answer the following questions:

() Why are certain cotton plants called Bt-cotton plants?

(ii) Why does Bt toxin not kill the bacterium that produces it but kill the insect that
ingests it?

(OR)

(i) What is biopiracy? Explain its significance with example. 3

(ü) State the initiative taken by Indian Parliament against biopiracy.

27. Study the following graph caregully and answer the following questions:

3
nchness
Specieš
Aroa

(a) If b denotes the relationship on log scale.

1. Describe a and b. How is slope represented?

S -ZA
2. Give the normal range of slope. locC + 2loH o.) -0.2
)Species diversity of plants (22%) is much less than that of animals (72%).

7
 will join later
segments. where the two DNA segments
on both the segments
(i) Sticky ends formed
DNA.
to form a recombinant

SECTION C
and answver the following questions
diagram carefully
22. Study the following

B 3

K(a) ldentify the A to E

takes place?
Y Explain how the processof decomposition of detritus -cata bol
mineraliron.
Ý3. Study the diagram carefully and answerthe following questions:

3
(i) Why do you see two different types of replicating strands in the given DNA 3
replication fork? Explain. Name these strands.

(iü) Explain the mechanism of DNA replication as suggested by Watson and

Crick.

The diagram below shows female reproductive system.

6
 under which growth curve A and B plotted in the graph
(a) State the conditions

possible with the help of formula

(b) What K represents in the graph?

2
Answer the following questions:

wheat that make it agood example of

(a)list any two characteristic features of flowers

wind pollination.

(b)It is observed that plant breeders carrying out wheat hybridization often take pollen

grains from the 'pollen banks'. Do you agree? Give one reason in support of your
answer.

2
Study the diagram carefully and answer the following questions:
19.

to evolution? Explain.
(a) What do these picture illustrate with reference

selection?
(b) How does industrial melanism support Darwin's theory of natural

Explain.

20. Study the structure of an antibody molecule is shown below and answer the

following questions

(a) ldentify A,B and C

(b) Explain how these molecules help in defense mechanism?

A segment DNA and that of a vector DNA are cut with restriction endonuclease to
of foreign
2
form a recombinant DNA. Show with the help of schematic diagrams.
(i) The set of palindromic nucleotide sequence of base pairs the EcoRI will recognize in

both the DNA segments.Mark the site at which EcoRI will act and cut both the

GAATTC
 Analyse the reasons for animals as compared to plants.
diversity of
greater

28. eBven tigure is the diagrammatic representation of artificial vector of PBk 322.

Cla Hind II

PvuI
B Bal I
Pst I

amptiteR -Sal I

pBR322

Prull

ldentify A to D
(iü) Ascientist tried to transform bacteria with a plasmid containing the gene of

interest inserted within the lacZ gene. Few of the bacteria took up the

plasmid while many didn't. He plated thismixture of bacteria on a medium 3

containing X-gal. Illustrate the results based on blue and white colonies in his
experiment.

SECTIOND
29. Biodiversity refers to diversity at alllevels of biological organisation ranging from
macromolecules inside the cells to biomes. There are three levels of diversity ;bacteriophage
with 100 genes and E.coli with 400 genes shów diversity X. it is related to number of genes
and their allele found in organisms. Diversity Y is shown by a community having three
different species represented by 4, 1 and 1 individuals and a community having three bird

species with two individuals of each species related to number and distribution of species()4ab
found in an area. Deserts, rainforests, coral reefs, etc. show diversity Z. It represents variety
of forms in the ecosystem due to diversity of niches, trophic levels and ecological processes.
d Loss speues ldavec
emhen
(a) There was loss of biodiversity in an ecosystem due to a new thatA
construçtión project in

area. What would be its impact on the ecosystem? State anythree.o

(b) List any three major causes of loss of biodiversity? vev
(c) Differentiate Ex-situ and In-situ conservation.

30. The Human Genome Project was an international scientific research project with the goal.of

determining the base pairs that make up human DNA, and of identifying, mapping and
sequencing allof the genes of the human genome from both a physical and a functional

standpoint. It started in 1990 and was completed in 2003.The methods involved two major
approaçhes which paved the pathway to understand human biology,to treat and diagnose a
disease and preventthousands of disorders.
(a) What are the two major approaches involved in "Human Genome Project'?
(b) Name the commonly used two vectors in the HGP? AC (AC
(c) The scientists involved in the above project identified about 1.4 million peculiar locations

in human genome'.Name these locations and state any one revolutionary significance.

(d) Apart from working on the principal ofautomated DNA sequencers,Frederick Sanger was
also credited for another significant development.What was that development?
31.
Describe the SECTIONE
post-zygoticevents
humans.Mention leadingto
any two implantationand
functionsof placenta
placenta. formationin

(OR) 5
()Draw a diagram
of an
and label enlarged view of T.S.
the of one
following parts: microsporangium of an angiosperm
(a)Tapetum (b)
Middle layer (c)
(iü) Endothecium (d)Microspore
Mention the
function of
tapetum. mother cells
(ii) Explain the
following
giving by
(a)Pollen grains reasons:
are well
(b) Pollen preserved as fossils.
tablets are in use by
people these days.
32. Refer to the given figure and answer the

P following

PO
questions.

Transcription
5

mRNA lac mRNA

Translation
A

larto
Bsala pmaas
(i) ldentify A and B in the given figure.
(ii) Describe the role of A that causes Switch on or Switch off mechanism.
(iiü) Explain HowB involved the formation of X,Y and Z by translation
process?

(OR)

Observe the fragment of hn-mRNA and

answer the following questions:

3' mRNA
Intron

Exon

(a) Explain and illustrate the steps involved to make fully processed hnRNA?
(b)Gene encoding RNA Polymerase land Ill have been affected by mutation in a
cell. Explain its impact on the synthesis of polypeptide, stating reasons.

33. Answer the following questions: 5

(a) Cancer one ofthe most dreaded diseases
is of humans. Explain 'Contact inhibition' and
'Metastasis' with respect to the disease.
(b) ldentify the group of genes which have been identified in normal cells that could lead to

cancer and how they do so?

(c) Analyze any two techniques which are useful to detect cancers of internal organs.

hstopathoyal
MR)
 given a-interferon as part of the treatment?
(0) Why are cancer patients often

(OR)

suitable
and Secondary Lymphoid organs with the help off
Explain the role of Primary

examples.

10