BIOLOGY

SOLUTION : PRACTICE PAPER – 2

SECTION – A
Q. 1. (i) (b) phytochrome
(ii) (a) closing of cuspid valves followed by the closing of the semilunar valves
(iii) (c) oxytocin
(iv) (b) interferons
(v) (d) Stream-lined body – aquatic adaptation
(vi) (d) SSBP
(vii) (b) gene frequency
(viii) (a) Anabaena
(ix) (c) 44
(x) (b) Become flaccid

Q. 2. (i) ABA causes efflux of K + ions from the guard cells and thus result in closure of
stomata, hence it is known as antitranspirant.
(ii) A bundle of axons within CNS is called a ‘tract’ while the one outside the CNS
is called ‘nerve’.
(iii) Phosphorus
(iv) Eurythermal and Stenothermal animals :
Eurythermal Stenothermal
1. Animals which can tolerate wide 1. Animals which can tolerate only
range of temperatures are called narrow range of temperature
eurythermal. fluctuations are called stenothermal.
2. Eurythermal animals show reduced 2. Stenothermal animals show high
temperature sensitivity. temperature sensitivity.
3. Body functions of eurythermal 3. Body functions of stenothermal
animals can occur at wide range of animals can occur at only narrow
temperature range. range of temperature range.
For example : Goat, man, cat, dog, For example : Insects, fishes, reptiles,
tiger, cow, sheep, monkey, crab, etc. snakes, etc.
(Any one point)
(v) Tt × tt is a test cross.
(vi) Starch-sugar interconversion theory :
Enzyme phosphorylase (Day-time)
Starch Sugar
(stomata (stomata
close) open)
Night-time

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

 (vii) Inducible enzyme : Bacteria like E.coli adapt to their chemical environment by
synthesizing certain enzymes depending upon the substrate present. Such
adaptive enzyme is called inducible enzyme.
(viii) Copper ions released from ‘Copper-T’ suppress the sperm motility and the
fertilizing capacity of sperms.

SECTION – B
Q. 3. (1) New species are introduced into any ecosystem either accidentally or intentionally.
Such introduction proves harmful for existing species. Sometimes even local
species get extinct. If such extinction happens, then this new species is called an
invasive species.
(2) For example, Parthenium or carrot grass, Lantana and water hyacinth (Eichhornia)
are invasive plant species.
(3) Nile perch which is a predator fish in Lake Victoria cause harm to 200 local
species of Cichlid fish.
(4) Clarias gariepinus (African catfish) was brought to India for aquaculture purpose.
This catfish species has proved harmful to endemic catfish varieties.
Since there is lack of local predator, this alien species survives and cause harmful
effect on local species.
Q. 4. (a) Bolting of rosette plants GA
(b) Epinasty Ethylene
(c) Closure of stomata ABA
(d) Proliferation of callus Kinetin

Q. 5. (a) Erythropoiesis : The process of formation of RBCs is called erythropoiesis.

(b) Erythrocytopenia : The decrease in the number of RBCs is called erythrocytopenia.
Q. 6. (1) The symptoms observed in Krishna were due to sympathetic nervous system.
Emergency conditions trigger sympathetic nervous system to stimulate adrenal
medulla.
(2) The cells of adrenal medulla secrete catecholamines like adrenaline and nor-
adrenaline.
(3) These hormones have direct effect on the pacemaker of the heart which causes
increase in the heart rate and other associated symptoms.
(4) This is a typical fright reaction caused by intervention of sympathetic nervous
system.
Q. 7. Chromosomal theory of inheritance : This theory was put forth by Sutton and
Boveri after studying parallel behaviour of genes and chromosomes during meiotic
division. This theory states following points :
(1) Chromosomal theory identifies chromosomes as the carrier of genetic material.
2 NAVNEET PRACTICE PAPERS : STANDARD XII
 (2) All the hereditary characters are transmitted by gametes. Nucleus of gametes, i.e.
sperms and ova of the parents contain chromosomes which transmit the heredity
to offspring.
(3) Chromosomes are found in pairs in somatic or diploid cells.
(4) During gamete formation, homologous chromosomes pair and segregate
independently at meiosis. The diploid condition is converted into haploid condition.
Thus each gamete contains only one chromosome of a pair.
(5) During fertilization, the union of sperm and egg restores the diploid number of
chromosomes.
Q. 8.
Growth (size or weight of the organism)

Diminishing
growth phase Stationary phase

Log or exponential
phase

Lag phase

Time
Logistic growth curve of population

Q. 9. Characteristics of Homo erectus :

(1) Homo erectus was also known as Java man or Peking man due to his fossils
obtained from these areas.
(2) He was also called ape man. He walked erect.
(3) He lived in the middle Pleistocene epoch about 1.5 million years ago.
(4) He was 5 feet in height with prognathous face, massive jaws, huge teeth and bony
eye brow ridges. Chin was absent.
(5) The cranial capacity was 900 cc.
(6) He was omnivorous and probably used fire and ate meat.
(Any four characteristics)

Q. 10. Spermatogenesis and Oogenesis :

Spermatogenesis Oogenesis
1. Spermatogenesis takes place in testis 1. Oogenesis takes place in ovaries in
in mature and fertile males. mature and fertile females.
2. From one spermatogonium four 2. From one oogonium one haploid
haploid sperms are formed during ovum and a polar body is formed
spermatogenesis. during oogenesis.

PRACTICE PAPER – BIOLOGY (SOLUTIONS) : STD. XII 3

 Spermatogenesis Oogenesis
3. Spermatid developed undergoes 3. There is no such process of
metamorphosis in the process of metamorphosis in oogenesis.
spermiogenesis.
4. Spermatid development takes place 4. Ootid development does not take
which later becomes a functional place during oogenesis. It develops
sperm. only after fertilization.
5. Spermatogonia, primary and 5. Oogonia, primary and secondary
secondary spermatocytes and oocytes are the stages formed during
spermatid are the stages of sperms oogenesis. Ootid formation occurs
formed during spermatogenesis. only after fertilization.
(Any four points)
Q. 11. Applications of tissue culture are as follows :
(1) Production of healthy plants from diseased plants using apical meristems as
explants.
(2) Production of stress resistant plants.
(3) Production of haploid plantlets by pollen culture.
(4) Production of secondary metabolites such as alkaloids, enzymes, hormones, etc.
(5) Multiplication of rare and endangered plants.
(6) Production of somaclonal variants.
(7) Use of micropropagation techniques to produce large number of genetically
identical plants.
(8) Protoplast culture.
(9) Tissue culture has applications in forestry, agriculture, horticulture, genetic
engineering and physiology. (Any four applications)
Q. 12. Ways to reduce noise pollution :
(1) Using sound absorbent materials or by muffling the noise, especially in the
industrial areas.
(2) Laws to reduce noise pollution should be strictly implemented.
(3) Blowing of horns should be discouraged in the areas of schools and hospitals.
(4) Firecrackers and loudspeakers should be completely banned.
(5) Supreme Court of India has banned loudspeakers at public gatherings after 10 pm.
Government rules regarding this should be strictly followed.
(6) Awareness about noise pollution caused during festivals and processions should
be spread among masses. (Any four ways)

Q. 13. (1) Water is an important constituent of cell. About 90 – 95% of protoplasm is water.
(2) Water in liquid state is best solvent in which various minerals and food molecules
are dissolved and transported.
4 NAVNEET PRACTICE PAPERS : STANDARD XII
 (3) Water acts as the thermal buffer, as it has high specific heat.
(4) Water molecules have high adhesive and cohesive forces of attraction. It can rise
in capillaries due to high surface tension and adhesive forces, e.g. ascent of sap
in plants.
Due to all these important factors, it is a significant molecule connecting physical
world with biological processes.

Q. 14. (1) Acrosome – (c) Secretion of Hyaluronidase

(2) Penetration of sperm into ovum – (a) Completion of IInd meiotic division of
secondary oocyte
(3) Formation of fertilization membrane – (d) Prevention of polyspermy
(4) Acrosin / Zona lysine – (b) Dissolution of zona pellucida

SECTION – C
Q. 15. (a) Nitrogen :
Role : Constituent of proteins as amino acids, nucleic acids, vitamins, hormones,
coenzymes, ATP and chlorophyll molecule.
Deficiency symptoms : Stunted growth and chlorosis.
(b) Phosphorus :
Role : Constituent of cell membrane, certain proteins, nucleic acids and
nucleotides, required for all phosphorylation reactions.
Deficiency symptoms : Poor growth, leaves dull green.
(c) Potassium :
Role : Determination of anion – cation balance in cell, necessary for protein
synthesis, involved in formation of cell membrane, opening and closing of stomata,
activates enzymes, helps in maintenance of turgidity of cells.
Deficiency symptoms : Yellow edges in leaves, premature death.
Q. 16. Factors affecting blood pressure :
(1) Cardiac output : Normal cardiac output is 5 lit / min. Increase in cardiac output
increases systolic pressure.
(2) Peripheral resistance : Peripheral resistance depends upon the diameter of blood
vessels. Decrease in diameter of arterioles and capillaries under the effect of
vasopressin cause increase in peripheral resistance and thereby increase in blood
pressure.
(3) Blood volume : Loss of blood in accidents decreases blood volume and thus
cause decrease in blood pressure.
(4) Viscosity of blood : Blood pressure is directly proportional to viscosity of blood.
(5) Age : Blood pressure increases with age due to increase in inelasticity of blood
vessels.

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

 (6) Venous return : Amount of blood brought to the heart via the veins per unit time
is called the venous return and it is directly proportional to blood pressure.
(7) Length and diameter of blood vessels : Blood pressure is directly proportional
to the total length of the blood vessel. Blood pressure can also be affected by
vasoconstriction or vasodilation.
(8) Gender : Females have slightly lower B.P. than males of her age before
menopause. However, the risk of high B.P. increases in the females after menopause
sets in. (Any three factors)

Q. 17. Column A Column B

(1) Forebrain Olfactory lobes, corpus callosum
(2) Midbrain Superior colliculi, iter
(3) Hindbrain Pons varolii, Vermis

Q. 18. (a) Amoebiasis :

Amoebiasis is usually transmitted by the following ways :
(1) The faecal-oral route.
(2) Through contact with dirty hands or objects.
(3) By anal-oral contact.
(4) Through contaminated food and water.
(b) Malaria :
(1) Malaria parasite is transmitted through the female Anopheles mosquito and
hence it is known as mosquito-borne disease. Mosquito acts as a vector.
(2) There are four species of Plasmodium, viz. P. vivax, P. falciparum, P. ovale
and P. malariae which transmit malaria.
(c) Ascariasis :
(1) Unsafe and unhygienic food and drinks contaminated with the eggs of Ascaris
are the main mode of transmission.
(2) Eggs hatch inside the intestine of the new host.
(3) The larvae pass through various organs and settle as adults in the digestive
system.
Q. 19.
Parents : Phenotype : Sickle-cell carrier × Sickle-cell carrier
Genotype : HbA HbS HbA HbS
Gametes :

Genotype : HbA HbA HbA Hbs HbA Hbs Hbs Hbs

Offspring : Phenotype : Normal Sickle-cell carrier Sickle-cell
1 2 anaemic
1 (dies)

6 NAVNEET PRACTICE PAPERS : STANDARD XII

Q. 20. (a) The nutrients are cycled from biotic organisms (bio) to abiotic components in the
earth (geo) and all these nutrients are in the form of chemicals, therefore, nutrient
cycling is called biogeochemical cycle.
(b) Food chain and food web :
Food chain Food web
1. Food chain is the linear sequence of 1. Food web is interconnections
organisms for feeding purpose. between many small food chains.
2. In food chain, the flow of energy is 2. In food web, the energy flow is
through a single straight pathway interconnected through numerous
from the lower trophic level to the food chains in the ecosystem.
higher trophic level.
3. In a food chain, members present at 3. In a food web, one organism can
higher trophic level feeds on only feed on multiple types of organisms.
single type of organisms.
4. Energy flow can be easily calculated 4. Energy flow is difficult to calculate
in food chain. in a food web.
5. In food chain, there is increased 5. In food web, there is increased
instability due to increasing number stability due to the presence of the
of separate and confined food complex food chains.
chains.
(Any two points)
Q. 21. (1) Archaeopteryx shows reptilian as well as avian characters.
(2) Reptilian characters are as follows :
(i) Jaws with homodont (all similar) teeth. Bones are non-pneumatic i.e. solid.
(ii) Ribs have a single head. Sternum without keel.
(iii) Abdominal ribs present which are like the crocodilian ribs.
(iv) Forearms have three digits ending in distinct claws while the hindlimb has
four digits ending in clawed digits.
(3) Avian characters are as follows :
(i) Forearms modified into wings.
(ii) Feathery exoskeleton.
(iii) Skull bones are completely fused.
(iv) Cranium is rounded with large orbits and a single condyle.
(v) Jaws are modified into beak.
(vi) Limb bones have first toe in opposable manner. Foot present with clawed digits.
Since Archaeopteryx showed characters of both the classes, it is considered
as the connecting link between reptiles and birds.

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

Q. 22. Event Physical process
1. Soaking of seeds Imbibition
2. Water entering guard cells Osmosis
3. Exchange of gases Diffusion
4. Loss of water in liquid form Guttation
5. Loss of water in vapour form Transpiration
6. Spreading of fragrance of incense stick Diffusion

Q. 23. Artificial methods of vegetative reproduction :

(1) Vegetative propagation is a kind of asexual reproduction which occurs with the
help of vegetative plant parts.
(2) Cutting and grafting are two artificial methods used to propagate desired varieties
of plants.
(3) In cutting, small pieces of plant parts having one or more buds are selected for
propagation, e.g. stem cutting – Rose, root cutting – Blackberry and leaf cutting –
Sansevieria.
(4) In grafting, two plant parts are joined together (Stock – rooted plant and
Scion – attached plant) and they continue their growth as one plant.
(5) When a single bud is grafted on stock plant it is called bud grafting, e.g. Rose,
Apple, Pear.
(6) Tissue culture is another method of vegetative reproduction in which a small
amount of plant tissue is grown to give many plantlets.

Q. 24. The goals of RCH can be achieved by the following ways :

(1) Sex education in schools is introduced. Proper and scientific information about
sexual organs and safe sexual acts should be given to students. They should be
made aware of sexually transmitted diseases (STD, AIDS), and problems related
to adolescence.
(2) Audio-visual and the print media should be used by government and non-
government organisations for creating awareness about reproductive health.
(3) Younger generation should be educated about family planning measures, pre-natal
and post-natal care of women and care of infant with knowledge about importance
of breastfeeding.
(4) Awareness should be spread about problems arising due to uncontrolled population
growth, sex abuse and sex related crimes. Necessary steps to prevent these to be
taken.
(5) Statutory ban on amniocentesis for sex determination is practised. This should be
known by all.
(6) Details of child immunization programmes should be understood.

8 NAVNEET PRACTICE PAPERS : STANDARD XII

 (7) New parents should get the training for newborn care so that infant and maternal
mortality rate can be reduced. (Any six points)

Q. 25. (a) Human genetic diseases like sickle-cell anaemia, thalassemia, Tay-sach’s disease,
cystic fibrosis, Huntington’s chorea, haemophilia, alkaptonuria, albinism, etc. are
caused by single gene defects. (Any two examples)
(b) Transgenic animals are genetically modified animals that are used in a wide range
of fields.
(1) In the field of medical research, transgenic animals like mice are used to
identify the functions of specific factors through over- or under-expression of
a modified gene (the inserted transgene). They are designed to study how
genes contribute to the development of disease. These animals are used to
investigate development of diseases like cancer, cystic fibrosis, rheumatoid
arthritis, etc.
(2) In toxicology field, they are used for detection of toxicants. They are used as
responsive test animals.
(3) Transgenic animals are used to evaluate a specific genetic change in molecular
biology studies.
(4) In pharmaceutical industry, transgenic animals are used for targeted production
of pharmaceutical proteins, drug production and product efficacy testing.
(5) They are also used in study of mammalian developmental genetics.
(6) Transgenic farm animals like cattle, sheep, poultry, pigs, etc. exhibit many
desirable traits as follows:
(a) Improved quantity and quality of meat
(b) Improved quality and quantity of milk
(c) More egg production
(d) Better quality and quantity of wool
(e) Disease resistance
(f) Production of low-cost pharmaceuticals and biologicals
(7) In the field of Biotechnology, they are used as producers of specific proteins.
(8) They are used in Xenografting. (Any four points)

Q. 26. (1) Many food preparations made at home involves the use of microorganisms. The
microbes Lactobacilli are used in the preparation of dhokla from gram flour and
buttermilk by the process of fermentation.
(2) Dosa and idlis are prepared by using batter of rice and black gram which is
fermented by air-borne Leuconostoc and Streptococcus bacteria.
(3) Large, fleshy fruiting bodies of some mushrooms and truffles are directly used as
food. It is sugar free, fat free food rich in proteins, vitamins, minerals and amino
acids. It is food with low calories.

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

 (4) Curd is prepared by inoculating milk with Lactobacillus acidophilus. Lactic acid
produced during fermentation causes coagulation and partial digestion of milk
protein casein and milk turns into curd. Buttermilk is the acidulated liquid left
after churning of butter from curd. (Any three points)

SECTION – D

Q. 27. (a) The figure ‘D’ is agranulocyte.

(b) Origin : Lymphoid stem cells
Structure : Agranulocytes do not show cytoplasmic granules and their nucleus is
not lobed.
(c) Agranulocytes are of two types, viz. lymphocytes and monocytes.
(d) Functions of agranulocytes : Lymphocytes are responsible for immune response
of body by producing antibodies and monocytes are phagocytic in function.

Q. 28. T.S. of spinal cord : Posterior median fissure

Posterior median
(1) Externally there are three septum
Dorsal root
Dorsal horn
meninges covering spinal White matter Lateral horn
cord : Duramater, arachnoid Central canal Ependyma
Grey matter Meninges
membrane and pia mater. Ventral horn
Ventral root
(2) Dorsoventrally there are two Anterior median fissure
fissures, the shallow dorsal or T.S. of spinal cord
posterior fissure and the deeper ventral or anterior fissure. From dorsal fissure a
dorsal septum extends inside.
(3) Neurocoel or central canal is situated in the centre of spinal cord.
(4) The central canal is filled with cerebrospinal fluid and is lined by cuboidal
epithelial cells called layer of ependyma.
(5) There is inner grey and outer white matter in the spinal cord. This grey matter is
in the shape of ‘H’ with two dorsolateral horns and two ventrolateral horns.
(6) Dorsal horns form dorsal roots and ventral horns form ventral roots.
(7) White matter is divided into three columns, viz., the dorsal funiculi, ventral
funiculi and lateral funiculi on either side.
(8) Ascending and descending tracts of nerve fibres arise from dorsal and ventral
roots of the spinal cord. Ascending tracts are sensory while descending tracts are
motor in nature.

Q. 29.
Template strand
3' 5'
Structural gene
5' 3'
Coding strand
Promoter Terminator

Transcription unit

10 NAVNEET PRACTICE PAPERS : STANDARD XII

 Transcription unit (Each transcribed segment of DNA) consists of the promoter, the
structural gene and the terminator.
(1) The promoter :
(a) The promoter is located towards 5′ end of structural gene, i.e. upstream.
(b) It is a DNA sequence that provides binding site for enzyme RNA polymerase.
(c) In prokaryotes, sigma factor sub unit of the enzyme recognizes the promoter.
(2) Structural genes :
(a) Template strand (Antisense strand) : DNA strand having 3′ → 5′ polarity acts
as template strand as DNA dependent-RNA polymerase catalyses
polymerization in 5′ → 3′ direction.
(b) Sense strand : The other strand of DNA having 5′ → 3′ polarity is
complementary to template strand. It is called as sense strand. The sequence
of bases in this strand, is same as in RNA (where Thymine is replaced by
Uracil). It is the actual coding strand.
(3) The terminator :
(a) The terminator is located at 3' end of coding strand, i.e. downstream.
(b) It defines the end of the transcription process.

Q. 30. Structure of a mature anatropous ovule :

(1) The ovule which has a bent axis and downwardly directed micropyle is called
anatropous ovule. It is the most common type of ovule in angiosperms.

Chalaza

Antipodals
Embryo sac
Secondary nucleus
Synergids
Egg
Outer integument
Inner integument
Nucellus
Hilum
Micropyle Funicle

Placenta

V. S. of an anatropous ovule

(2) The matured anatropous ovule consists of two parts, viz. the stalk and the body.
The stalk of the ovule is called the funicle or funiculus. The funicle attaches the
ovule with the placenta.
(3) The point at which the funicle is attached to the body of the ovule is called hilum.

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

 (4) Nucellus : It is made up of diploid parenchymatous cells. The basal part of the
nucellus is called chalaza. The protective coverings of the nucellus are called
integuments.
(5) Micropyle : The integuments do not completely cover the nucellus. They leave
a small opening called micropyle at the tip.
(6) Embryo sac : In a mature ovule, the nucellus shows an oval-shaped structure
towards its micropylar end called embryo sac or female gametophyte.

Q. 31. (a) Passenger DNA : It is a cleaved DNA fragment containing desired gene, isolated
and selected for cloning.
(b) Chimeric DNA : It is the combination of vector DNA and foreign DNA. It is also
called recombinant DNA.
(c) Transformed cell : The competent host cell which has taken up r-DNA is called
transformed cell.
(d) Restriction site : The restriction enzymes recognize and cut DNA at specific
sequences called restriction sites.
————

12 NAVNEET PRACTICE PAPERS : STANDARD XII