BIOLOGY

SOLUTION : PRACTICE PAPER – 4

SECTION – A

Q. 1. (i) (a) Mice died and showed live S-cells

(ii) (d) Apis mellifera–Wild bee
(iii) (b) Keratin
(iv) (d) 125
(v) (a) Copper, iron, silicon, nickel and gold
(vi) (b) aldosterone
(vii) (d) D.P. D. = O.P. – T.P
(viii) (c) 10th to 17th day
(ix) (c) 0.1
(x) (d) Pliocene

Q. 2. (i) Small part of activated sludge is passed back into aeration tank.
(ii) Anaemia is disorder caused due to the deficiency of haemoglobin while leukemia
is blood cancer in which there is abnormal increase in the number of white
blood cells.
(iii) If E.coli bacteria do not have lactose in the surrounding medium as a source of
energy, lac operon is switched off.
(iv) Red nucleus plays an important role in controlling posture and muscle tone,
modifying some motor activities and motor coordination.
(v) Holandric genes or Y-linked genes
(vi) (a) Interspecific competition :
Leopard and lion competing for a same prey.
Sheep and cow competing for grazing in the same land.
(Any one example)
(b) Intraspecific competition :
Two dogs fighting for same food.
Two tomcats fighting for their territory. (Any one example)

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 1

 (vii) Primary and secondary succession :
Primary succession Secondary succession
1. The primary succession starts in the 1. The secondary succession starts in an
area where no living organisms ever area which has lost all the living
existed. organisms once existed.
2. Areas where primary succession starts 2. Abandoned farm, cut or burnt forest,
are bare rock, newly formed pond, flooded land, etc. are areas where
newly cooled lava, etc. secondary succession begins.
3. Primary succession is a very slow 3. Secondary succession is comparatively
process. a faster process.
(Any one point)
(viii) Water is conducted upwards in plants, due to vascular system of xylem, mainly
through vessels and tracheids. The pull created in this continuous channel of
water helps the water go upwards.

SECTION – B
Q. 3. Erythrocytes :
(1) Erythrocytes or red blood corpuscles are circular, biconcave, enucleated cells.
(2) The RBC size : 7 μm in diameter and 2.5 μm in thickness.
(3) The RBC count : 5.1 to 5.8 million RBCs / cu mm of blood in an adult male and
4.3 to 5.2 million / cu mm in an adult female.
(4) The average life span of RBC : 120 days.
(5) RBCs are formed by the process of erythropoiesis. In foetus, RBC formation
takes place in liver and spleen whereas in adults it occurs in red bone marrow.
(6) The old and worn out RBCs are destroyed in liver and spleen.
(7) Polycythemia is an increase in number of RBCs while erythrocytopenia is decrease
in their (RBCs) number. (Any four points)

Q. 4. (a) Agrobacterium tumefaciens.

(b) pBR 322.

Q. 5. Evidences of Darwinism :
(1) Height of neck of Giraffe : Long-necked Giraffe could pluck and eat more
leaves from tall trees and woody climbers. So it was well adapted to the
environment. Short-necked one could not get food and thus perished in the
struggle. This adaptation was transmitted to their offspring.
(2) Black colour peppered moths : The example of industrial melanism seen in
U.K. is an excellent example of natural selection in action. Black coloured moths
evolved gradually as new species from the previous white coloured forms.

2 NAVNEET PRACTICE PAPERS : STANDARD XII

 (3) DDT resistance in mosquitoes : Intensive DDT spraying destroyed all types of
mosquitoes. Some mosquitoes developed resistance to DDT and survived in spite
of DDT spray. They reproduced more and were thus selected naturally.
(Any two evidences)
Q. 6. Human female is referred to as carrier of colour blindness because of the following
reasons :
(1) Females possess double X-chromosomes in her cell.
(2) If one X-chromosome is carrying recessive gene for colour blindness, her other
dominant X hides the expression of colour blindness and hence she does not
become a patient.
(3) But such female can carry the defective gene to her progeny. Thus she is called
carrier of colour-blindness.
(4) A female having one recessive gene on X-chromosome is a carrier female, while
a female possessing both recessive genes on both the X-chromosomes will be
colour blind which is very rare.

Q. 7. (a) The Intra-uterine contraceptive device shown in the diagram is Lippes loop.
(b) It is a plastic double ‘S’ loop. It attracts the macrophages stimulating them to
accumulate in the uterine cavity. Macrophages increase phagocytosis of sperms
within the uterus and acts as a contraceptive.
Q. 8. Seed-germination

Meristem

Cell division
Plasmatic growth

Cell elongation

Cell maturation

Mature cell

Senescence

Death
Q. 9. (1) Marine fish has its own osmoregulation which is different from the osmoregulation
seen in fresh water fish.
(2) In marine water, the ambient salinity is more than the concentration of ions in the
body. But in fresh water reverse is the case.
(3) Therefore, marine fish has different machinery to cope up with high saline
environment.
(4) Therefore, it cannot survive in fresh water as its osmoregulation is not possible
in less saline waters.
PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 3
Q. 10. Desired characteristics of ideal cloning vector are as follows :
(1) Vector should be able to replicate independently (through ori gene), so that as
vector replicates, multiple copies of the DNA insert are also produced.
(2) It should be able to easily transferred into host cells.
(3) It should have suitable control elements like promoter, operator, ribosomal binding
sites, etc.
(4) It should have marker genes for antibiotic resistance and restriction enzyme
recognition sites within them.
Q. 11. (1) The loss of water in the form of water vapour is called transpiration.
(2) About 90 – 93% of transpiration occurs through stomata, small apertures located
in the epidermis of leaves.
(3) For this process stomata must remain open and then only gaseous exchange by
diffusion takes places.
(4) Gaseous exchange is necessary for respiration and photosynthesis. If stomata
remain closed then it will affect productivity of plant.
(5) The process is necessary evil because water which is important for plant is lost
in the process.
(6) At the same time it helps in absorption of water and its translocation. Hence it
cannot be avoided.
Thus, transpiration is called a necessary evil.
Q. 12. (1) Auxin – (d) Apical dominance
(2) Cytokinin – (c) Promotion of growth of lateral buds
(3) Gibberellins – (a) Bolting in rosette plants
(4) Abscissic acid – (b) Stimulate flowering in SDP
Q. 13. Exteroceptors and Interoceptors :
Exteroceptors Interoceptors
1. Receptors receiving stimuli from 1. Receptors receiving stimuli from
outer environment of the body are inside the body are called interoceptors.
called exteroceptors.
2. These are somatic receptors. 2. These are visceral receptors.
3. Exteroceptors keep the body informed 3. Interoceptors keep the homeostasis in
about changes in the environment like the body by receiving stimuli from
temperature, pressure, touch, etc. inside the body.
4. Mechanoreceptors, thermoreceptors, 4. Propioceptors, enteroceptors,
chemical receptors, photoreceptors baroceptors are the different types of
and statoacoustic receptors are the interoceptors.
different types of exteroceptors.
(Any four points)
4 NAVNEET PRACTICE PAPERS : STANDARD XII
Q. 14. Sponges reproduce by the following methods :
(A) Gemmule formation : In sponges, during unfavourable period, gemmule is
produced. It is an internal bud.
Archaeocytes which are dormant cells are seen in the aggregation in gemmule
and are capable of developing into a new organism.
Amoebocytes are other cells, which secrete thick resistant layer of secretion
which is coated around archaeocytes. When favourable conditions of water and
temperature return back, the gemmules can develop into new individuals by
hatching.
(B) Budding : It is a simple method of asexual reproduction normally occurring in
favourable conditions. A small outgrowth (bud) is produced from the body.
It develops as a bud, gets detached from the parent and grows into a new
individual.

SECTION – C
Q. 15. (1) Opioids :
(1) Opioids bind to specific opioid receptors present in the central nervous system
and in gastrointestinal tract.
(2) They are depressants and slow down the body functions.
(2) Cannabinoids :
(1) Cannabinoids interact with receptors in the brain.
(2) They affect cardiovascular system of the body.
(3) Morphine :
(1) Morphine is an effective sedative and pain killer when used for medicinal
purpose.
(2) When abused it affects physical, physiological and psychological functions.

Q. 16. (A) Tachycardia : Higher heart rate over 100 beats per minute is called tachycardia.
(B) Single circulation and double circulation :
Single circulation Double circulation
1. Blood flows only once through the 1. Blood flows twice through the heart
heart in a complete cycle. during one complete circulation.
Systemic – to and fro from heart to
body and pulmonary – to and fro
from heart to lungs.
2. Heart pumps deoxygenated blood 2. Heart pumps both deoxygenated and
only. oxygenated blood to lungs and body
respectively.
3. Blood is oxygenated in gills. 3. Blood is oxygenated in lungs.

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 5

 Single circulation Double circulation
4. Occurs only in fishes. 4. Occurs in amphibians, reptiles, birds
and mammals.
Q. 17. (a) 6 haploid cells : 2 synergids, 1 egg cell, 3 antipodals.
(b) Autogamy and xenogamy :
Autogamy (Self-pollination) Xenogamy (Cross pollination)
1. In self-pollination, bisexual flower is 1. In cross pollination, the pollen grains
pollinated by its own pollen grains. from the anther are carried to the stigma
of another flower of same species.
2. Self-pollination does not depend upon 2. Cross pollination does depend upon
external agents for pollination. external agents for pollination.
3. Self-pollination is economical as there 3. Cross pollination is not economical as
is no wastage of pollen grains. there is wastage of pollen grains
during transfer.
4. Offspring are genetically similar to 4. Offspring are genetically varied due
their parents. to recombination.

Q. 18. (1) Teeth are innervated by branches of trigeminal nerve (V cranial nerve).
(2) Extraction of tooth stimulates this nerve which then carries the impulse
(action potential) to the pain centre of the brain where the pain is perceived.
(3) To avoid this, dentists give anaesthesia, to numb the nerve.
(4) Action potential is not generated due to anaesthesia.
(5) Hence the pain is not perceived.
(6) Similarly, some common pain killers act on the nerve endings and pain centres of
the brain, preventing generation of action potential.

Q. 19. (a) Homologous organs : Flipper of whale and wing of bird, Vertebrate heart and
brain
(b) Analogous organs : Wing of insect and wing of bird, Eye of octopus and eye of
mammal
(c) Vestigial organs : Nictitating membrane, wisdom tooth
(Any one example of each organ)
Q. 20. (a) Exhaust gas scrubber.
(b) Exhaust gas scrubbers are used to clean air by removing both dust and gases.
(c) The exhaust is passed through dry or wet packing material. When it is done, gases
like SO2 are removed. For this purpose, the exhaust is passed through a spray of
water or lime.
Q. 21. Cross of co-dominance :
Coat colour in cattle
Red female RR × White male WW

6 NAVNEET PRACTICE PAPERS : STANDARD XII

 P1 generation : RR × WW
Gametes : R and W
F1 generation : RW (Roan coloured)
F2 generation : RW × RW
♂ R W
♀
R RR RW
W RW WW
Genotypic ratio : 1 RR : 2 RW : 1 WW
Phenotypic ratio : 1 Red : 2 Roan : 1 White
Q. 22. (1) The unfertilized egg released through ovary at the time of ovulation is a secondary
oocyte.

Vitelline membrane

Perivitelline space

Zona pellucida
Germinal vesicle
Corona radiata

First polar body

Unfertilized egg / Ovum

(2) It is rounded, non-motile and haploid, non-cleidoic and microlecithal female

gamete.
(3) The size is approximately 0.1 mm (100 microns).
(4) It has abundant cytoplasm called ooplasm which contains a large eccentric and
prominent nucleus called germinal vesicle.
(5) Centrioles are absent in secondary oocyte.
(6) Various coverings seen around the oocyte are (i) vitelline membrane (ii) zona
pellucida (iii) corona radiata.
(7) The cells of corona radiata are glued together with hyaluronic acid. Between
vitelline membrane and zona pellucida, there is perivitelline space which lodges
first polar body. This end is called animal pole and the opposite is called vegetal
pole.
Q. 23. (a) 500,000 primary consumers are supporting 5000 secondary consumers.
If the numbers are reversed, i.e. if primary consumers are lesser than secondary
consumers, then the secondary consumers will have fierce competition and will
lead to decline in their number too. The pyramid of numbers will get inverted in
such case.
(b) If we plot the number of insects on a single tree, smaller birds feeding on insects,
and parasites on those birds, we get an inverted pyramid.

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 7

 (c) If large birds are feeding on smaller insect eating birds, their population will
decrease. This will result into increased number of insects as there will be no
check on the insect population due to loss of smaller predator birds. If larger birds
keep on feeding constantly and unchecked on smaller birds, the smaller ones will
eventually become lesser and lesser in their population and this in turn will starve
the larger birds too, leading in decrease of their population too.
Q. 24. (1) Biopiracy is defined as ‘theft of various natural products and then selling them
by getting patent without giving any benefits or compensation back to the host
country’.
(2) It is unauthorized misappropriation of any biological resource and traditional
knowledge.
(3) It is bio-patenting of bio-resource or traditional knowledge of another nation
without proper permission of the concerned nation or unlawful exploitation and
use of bioresources without giving compensation.
(4) Following are the examples of biopiracy :
(a) Patenting of Neem (Azadirachta indica) :
(i) Pirating India’s traditional knowledge about the properties and uses of
neem, the USDA and an American MNC W.R. Grace sought a patent
from the European Patent Office (EPO) on the “method for controlling
on plants by the aid of hydrophobic extracted neem oil,” in the early 90s.
(ii) The patenting of the fungicidal properties of Neem, was an example of
biopiracy.
(b) Patenting of Basmati :
(i) Texmati is a trade name of “Basmati rice line and grains” for which
Texas based American company Rice Tec Inc was awarded a patent by
the US Patent and Trademark Office (USPTO) in 1997.
(ii) This is a case of biopiracy as Basmati is a long-grained, aromatic variety
of rice indigenous to the Indian subcontinent.
(iii) Very broad claims about “inventing” the said rice was the basis of patent
application.
(iv) The UPSTO has rejected all the claims due to people movement against
Rice Tec in March 2001.
(c) Haldi (Turmeric) Biopiracy :
(i) A patent claim about the healing properties of Haldi was made by two
American researchers of Indian origin of the University of Mississippi
Medical Center, to the US Patent and Trademark Office.
(ii) They were granted a patent in March 1995.
(iii) This is an example of biopiracy because healing properties of Haldi is
not a new discovery, but it is a traditional knowledge in ayurvedas for
centuries.

8 NAVNEET PRACTICE PAPERS : STANDARD XII

 (iv) The Council of Scientific and Industrial Research (CSIR) applied to the
US Patent Office for a re-examination and they realized the mistake and
cancelled the patent. (Any two examples)

Q. 25. (1) Donnan equilibrium is a process of passive absorption of minerals in plants which
is without any expenditure of energy.
(2) It is assumed that certain anions after their entry by diffusion into the cell get
fixed on inner side of cell membrane. Additional mobile cations are needed to
balance this fixed anions as they cannot diffuse outside. Concentration of cations
thus increases due to accumulation.
(3) This passive absorption of anions or cations from exterior against their
concentration gradients so as to neutralize the effect of cations or anions is known
as Donnan equilibrium.

Q. 26. Biological importance of water :

(1) Water is absolutely necessary for life.
(2) It is a major constituent of protoplasm.
(3) It provides aqueous medium for various metabolic reactions that take place in
plant.
(4) It is a raw material for photosynthesis.
(5) It helps in maintaining the turgidity of cells.
(6) It is an excellent solvent for various organic materials.
(7) It is a transporting medium for dissolved minerals.
(8) It is a thermal buffer. (Any six points)

SECTION – D
Q. 27. Methods of fish preservation :
(1) Fish is a highly perishable commodity. In order to prevent the spoilage of fish
after catching, the fish preservation is done.
(2) The different methods of fish preservation are as follows :
(a) Chilling : This involves covering the fish with layers of ice. Ice is effective
for short term preservation. It inhibits the activity of autolytic enzymes.
(b) Freezing : It is a long duration preservation method. Fishes are freezed at
0°C to − 20°C. This also inhibits autolytic enzyme activities and slows down
bacterial growth.
(c) Freeze drying : It involves sublimation of water from frozen fish under
vacuum.
(d) Sun drying : Fishes are dried in sunlight to remove moisture. This inhibits
the growth of microorganisms that spoil the fish.

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 9

 (e) Smoke drying : Smoke is prepared by burning woods with less resinous
matter. Bacteria are destroyed by the acid content of the smoke. Smoking also
gives the characteristic colour, taste and odour to fish.
(f) Salting : Salt removes the moisture from the fish tissues by osmosis. High
salt concentration destroys autolytic enzymes and halts bacterial activity.
(g) Canning : Canning involves sealing the food in a container, heat ‘sterilising’
the sealed unit and cooling it to ambient temperature for subsequent storage.
(Any four methods)
Q. 28. (a) Breathing through nose is better than breathing through the mouth because of the
following reasons :
(1) The nostrils are smaller than the mouth so air exhaled through the nose creates
a backflow of air into the lungs.
(2) As we exhale more slowly through the nose than we do through the mouth,
the lungs have more time to extract oxygen from the air that we have already
taken in.
(3) The hairs inside nostrils filter any dust particles and microbes in the air and
it only lets the clean air pass through.
(4) The air gets warm and humidified in nostrils as it passes into our bodies.
(5) Moreover breathing through the mouth can dry the oral cavity and lead to bad
breath, gum disease and tooth decay.
(b)

Organism Respiratory surface / organ

1. Insects Tracheal tubes and spiracles
2. Amphibian tadpoles of frog, salamanders External gills
3. Fish Internal gills
4. Reptiles, Birds and Mammals Lungs

Q. 29. (a) Column A Column B

1. Initiator codon (iv) AUG
2. Stop codons (iii) UAA, (v) UAG, (vi) UGA
3. Codon that codes for Phenylalanin (i) UUU
4. Codon that codes for leucine (ii) CUA

10 NAVNEET PRACTICE PAPERS : STANDARD XII

 (b)
Glutamic acid

Amino acid
3' attachment site

t-RNA 5'
Intramolecular
base pairing

Anticodon loop
Anticodon
m-RNA

Clover leaf structure of t-RNA carrying glutamic acid.

Q. 30. (a) Budding :

(1) It is a type of asexual reproduction. It is observed in favourable condition.

Chain of buds

Mother cell

Budding in yeast

(2) It is of very common occurrence in unicellular fungi yeast and algae

Protosiphon.
(3) Mother cell produces small outgrowth which is known as bud.
(4) Buds may be one or more and on separation, they grow as new individual.
(b) Spore formation / Sporulation :
(1) It is a type of asexual reproduction. It is of very common occurrence in lower
plants.

Zoospores

Parent cell
(Zoosporangium)

Zoospores in Chlamydomonas
(2) It occurs by production of motile zoospores that are formed in sporangia.

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 11

 (3) Flagellated zoospores when liberated can grow independently into new
individuals.
(4) Biflagellate zoospores are formed in algae Chlamydomonas.

Q. 31. (1) Homeostasis is maintenance of constant internal environment of the body.

(2) When certain hormones from any endocrine glands are secreted in excess quantity,
the inhibiting factors from hypothalamus, automatically exert negative feedback
and stop the production of stimulating hormones from pituitary.
(3) Similarly, if any hormone is in deficit, then the concerned gland is given message
through releasing factor. This way the hormone production remains in a balanced
state or homeostasis.
(4) Though most of the endocrine glands are under the influence of pituitary gland,
it is in turn controlled by hypothalamus.
(5) Hypothalamus secretes releasing factors and inhibiting factors and hence regulate
the secretions of pituitary (hypophysis).
(6) Hypothalamus forms the hypothalamo-hypophyseal axis through which
transportation of neurohormones take place.
Following are the releasing and inhibiting factors produced by hypothalamus :
(1) Somatotropin / GHRF : It stimulates release of growth hormone.
(2) Somatostatin / GHRIF : It inhibits the release of growth hormone.
(3) Adrenocorticotropin Releasing Hormone / CRF : It stimulates the release
of ACTH by the anterior pituitary gland.
(4) Thyrotropin Releasing Hormone / TRF : It stimulates the release of TSH by
anterior pituitary gland.
(5) Gonadotropin Releasing Hormone (GnRH) : It stimulates pituitary to
secrete gonadotropins.
(6) Prolactin Inhibiting Hormone (Prolactostatin) : It inhibits prolactin
released by anterior pituitary gland.
(7) Gastrin Releasing Peptide (GRP).
(8) Gastric Inhibitory Polypeptide (GIP). (Any four factors)
————

12 NAVNEET PRACTICE PAPERS : STANDARD XII