BIOLOGY
SOLUTION : PRACTICE PAPER – 5
SECTION – A
Q. 1. (i) (b) prevent fertilization
(ii) (c) synapsis
(iii) (b) i, iv, iii, ii
(iv) (c) Simian gap
(v) (d) meristematic region.
(vi) (d) anti-gibberellin
(vii) (b) Western blot
(viii) (a) Invasive species
(ix) (b) latitudinal gradient
(x) (c) Climax community
Q. 2. (i) pBR 322 is the most commonly used plasmid in r-DNA technology.
(ii) Rhizosphere is the microenvironment that surrounds the root, from where roots
can absorb water.
(iii) Cytokinins promote growth of lateral buds by cell division and thus control apical
dominance.
(iv)
Gene therapy is the treatment of genetic disorders by replacing, altering or
supplementing a gene that is absent or abnormal and whose absence or abnormality
is responsible for the disease.
(v) Organisms which can tolerate wide range of salinities are called euryhaline while
organisms which are restricted only to a narrow range of salinity are called
stenohaline.
(vi) Ecological succession is the gradual and predictable change in the species
composition of a given area.
(vii) In Maharashtra, there are 5 national parks and 11 sanctuaries.
(viii) (1) Hyalobatidae
(2) Pongidae
(3) Hominidae
solutions to navneet practice papers : std. xii 1
SECTION – B
Q. 3. 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; E.g. Pea to recombination. E.g. Food and fibre
crops – Maize, Rice.
Q. 4. (a) Non-disjunction : Non-disjunction is the phenomenon in which chromosomes
fail to separate at the time of cell division, resulting in abnormal chromosomal
combinations.
(b)
Homologous Chromosomes : The morphologically, genetically and structurally
essentially identical chromosomes present in a diploid cell are called homologous
chromosomes.
Q. 5.
Functional genomics is a branch of genomics that involves the study of functions of
all gene sequences and their expressions in organisms.
Q. 6. (1) Water is in liquid state at room temperature.
(2) It is best solvent for most of the solutes. Thus called universal solvent.
(3) It is inert inorganic compound with neutral pH i.e. pH 7 when in pure form.
(4) Hence it is best medium for dissolved minerals.
Q. 7. Column A Column B
(1) Shedding of leaves Abscissic acid
(2) Induce flowering in LDP GA
(3) Apical dominance IAA
(4) Induce RNA synthesis Cytokinin
2 solutions to navneet practice papers : std. xii
Q. 8. (1) Glucagon – (ii) Islets of Langerhans
(2) adrenaline – (iv) Medulla
(3) Somatotropins – (iii) Adenohypophysis
(4) ADH – (i) Neurohypophysis
Q. 9. Goitres are of following two types.
Simple goitre or endemic goitre : Caused due to iodine deficiency in the diet
(i)
causing lesser iodine in blood. In an attempt to compensate this deficiency more
iodine from blood is absorbed. Due to which the blood supply to the gland increases
which results into swelling of the thyroid.
Exophthalmic goitre or toxic goitre : Caused due to hyperactive thyroid gland.
(ii)
This can happen if there is overstimulation of thyroid due to excess of ACTH.
This disorder is also called Grave’s disease or hyperthyroidism.
Q. 10. (1) Vitamins are nitrogenous organic compounds, required in minute quantities for
normal growth and development of the body.
(2) The microbes are involved in the industrial production of vitamins like thiamine
(vitamin B1), riboflavin (vitamin B2), pyridoxine, folic acid, pantothenic acid,
biotin, vitamin B12, ascorbic acid (vitamin C), beta-carotene (provitamin A) and
ergosterol (provitamin D).
(3) Examples of some vitamins produced by fermentation using different microbial
sources are –
(i) Vitamin B2 – Neurospora gossypii, Eremothecium ashbyi
(ii) Vitamin B12 – Pseudomonas denitrificans
(iii) Vitamin C – Aspergillus niger
Q. 11. (1) The two types of nucleases are exonucleases and endonucleases.
(2) Exonucleases remove nucleotides from the ends of the DNA.
(3) Endonucleases are those enzymes that have ability to make cuts at specific
positions within the DNA molecule.
(4) Of the endonucleases, restriction endonucleases serve as the molecular scissors in
genetic engineering experiments.
(5) They are used for cutting DNA molecules at specific predetermined sites. This is
needed for gene cloning or recombinant DNA technology.
solutions to navneet practice papers : std. xii 3
Q. 12. Hibernation Aestivation
1. Hibernation is winter sleep shown by 1. Aestivation is the type of summer
some warm-blooded and some cold- sleep, shown by cold-blooded animals.
blooded animals.
2. It is for the whole winter. 2. It is of short duration.
3. The animals look out for the warmer 3. Animals search for the moist, shady
place to enter into hibernation. and cool place to sleep.
4.
Metabolic activities of hibernators 4.
Metabolic activities of aestivators
slow down in this dormant stage. remain low during aestivation period.
Q. 13. (a) The climax community remains stable as long as the environment remains
unchanged.
(b) Small phytoplankton are the pioneers in the aquatic habitat during primary
succession.
Q. 14. (1) Walter Rosen – (d) Coined the term biodiversity.
(2) David Tillman – (c) Productivity stability Hypothesis.
(3) Paul Ehrlich – (b) Rivet Popper Hypothesis.
(4) Edward Wilson – (a) Popularisation of term biodiversity.
SECTION – C
Q. 15. (1) Unisexuality, dichogamy, prepotency, heteromorphy and herkogamy are the
outbreeding devices.
(2) Unisexuality : The plants bear either male or female flowers. Due to unisexual
nature, self-pollination is avoided. Plants are either dioecious, e.g. Papaya or
monoecious, e.g. maize.
(3) Heteromorphy : In same plants different types of flowers are produced. In these
flowers, stigmas and anthers are situated at different levels. There is heterostyly
and heteroanthy. This prevents self-pollination, e.g. Primrose.
(4) Herkogamy : In bisexual flowers we may come across mechanical device to
prevent self-pollination. Natural physical barrier avoids contact of pollens with
stigma. E.g. Calotropis where pollinia are situated below the stigma.
4 solutions to navneet practice papers : std. xii
Q. 16.
Apomixis
Gametophytic cell produces embryo Sporophytic cell produces embryo
Apogamy Apospory
Embryo from Embryo from other Unreduced embryo sac Nucellar cells
egg haploid cells from megaspore mother form embryo sac
cell
Parthenogenesis Sterile plants
Diplospory Apomictic
E.g. Nicotiana embryo sac
E.g. Texacum
Q. 17. (1) A : Seminiferous tubule
Function : Seminiferous tubules produce sperms by spermatogenesis.
(2) B : Vas deferens
Function : Vas deferens carry sperm from epididymis to ejaculatory duct.
Q. 18. X-chromosome Y-chromosome
1. X-chromosome is straight, rod like and 1. Y-chromosome is shorter chromosome
longer than Y chromosome. It is which is acrocentric.
metacentric.
2. X-chromosome has large amount of 2.
Y-chromosome has small amount of
euchromatin and small amount of euchromatin and large amount of
heterochromatin. heterochromatin.
3. X-chromosome has large amount of 3.
Y-chromosome has less amount of
DNA, hence it is genetically active DNA, hence it is genetically less active
due to more genes. or inert due to lesser genes.
4. Non-homologous region of 4. Non-homologous region of
X-chromosome is longer and contains Y-chromosome is shorter and contains
more genes. lesser genes.
5. Contains X-linked genes on non- 5. Contains Y-linked genes on non-
homologous region. homologous region.
6. X-chromosome is present in men as 6. Y-chromosome is present only in men.
well as women.
Q. 19. A : Infection B : Blending C : Centrifugation
Scientists who carried out experiment are Alfred Hershey and Martha Chase.
solutions to navneet practice papers : std. xii 5
Q. 20. (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.
(3) Water acts as the thermal buffer has high specific heat.
(4) Water molecules have high adhesive and cohesive forces of attraction.
(5) It can rise in capillaries due to high surface tension and adhesive forces. e.g.
Ascent of sap in plants.
(6) Due to all these important factors it is a significant molecule connecting physical
world with biological processes.
Q. 21. (1) Phytohormones or plant growth regulators are internal factors that influence
growth.
(2) They inhibit, promote or modify the plant growth.
(3) Plant hormones are organic substances produced naturally in plants and required
in small amount.
(4) Their place of production and site of the activity are different.
(5) Auxins, gibberellins, cytokinins are growth promoters and ethylene, abscissic acid
are growth inhibitors.
Q. 22. To stop the spread of infectious diseases following public health measures should be
taken :
(1) Before and after preparing food, before eating and after using the toilet, hand
wash is a must. Hands should be washed often.
(2) Vaccinations : Immunization helps us to protect against contracting many diseases.
Therefore, timely vaccination should be taken. Especially at the time of epidemic,
one must keep distance from infected area or get vaccinated.
(3) One must be at home if there are signs and symptoms of an infection. By going
out, we may infect other healthy persons.
(4) Proper diet and exercise should be followed to improve one’s own immunity.
(5) Hygiene should be utmost in the kitchen and dining area. One must take care
while eating uncovered and leftover food.
(6) Bathroom and toilet should be cleaned daily as there can be a high concentration
of bacteria or other infectious agents in these areas.
Q. 23. (1) Disorders of adrenal cortical secretions are caused due to hyposecretion and
hypersecretion of adrenal corticoid hormones.
(2) Hyposecretion of corticosteroids causes Addison’s disease.
(3) The symptoms of Addison’s disease are low blood sugar, low body temperature,
feeble heart action, low BP, acidosis, low Na+ and K+ concentration in plasma,
6 solutions to navneet practice papers : std. xii
excessive loss of Na+ and water in urine, impaired kidney functioning and kidney
failure, etc. It leads to weight loss, general weakness, nausea, vomiting and
diarrhoea.
(4) Hypersecretion of corticoids causes Cushing’s disease.
(5) The symptoms of Cushing’s disease are high blood sugar level, glucosuria,
alkalosis, enhancement of total quantity of electrolytes in extracellular fluid,
polydipsia, increased BP, muscle paralysis, obesity, wasting of limb muscles, etc
Q. 24. Organism Habitat Respiratory surface/organ
1. Insects Terrestrial Tracheal tubes and spiracles
2. Amphibian tadpoles of frog, Aquatic External gills
salamanders
3. Fish Aquatic Internal gills
4. Reptiles, Birds and Mammals Terrestrial Lungs
Q. 25. (a) Enzyme is EcoRI.
(b) Palindrome is a DNA sequence which when read in opposite direction (3’ to 5’
or 5’ to 3’) it reads same.
(c) Enzyme in the given diagram cuts DNA to produce sticky ends.
Q. 26. Factors affecting blood pressure are :
Cardiac output : Normal cardiac output is 5 lit/min. Increase in cardiac output
(1)
increases systolic pressure.
Peripheral resistance : Peripheral resistance depends upon the diameter of blood
(2)
vessels. Decrease in diameter of arterioles and capillaries under the effect of
vasopressin causes increase in peripheral resistance and thereby increase in blood
pressure.
Blood volume : Loss of blood in accidents decreases blood volume and thus
(3)
causes decrease in blood pressure.
Viscosity of blood : Blood pressure is directly proportional to viscosity of blood.
(4)
Age : Blood pressure increases with age due to increase in inelasticity of blood
(5)
vessels.
Venous return : Amount of blood brought to the heart via the veins per unit time
(6)
is called the venous return and it is directly proportional to blood pressure.
solutions to navneet practice papers : std. xii 7
SECTION – D
Q. 27. (1) Cleavage is a rapid mitotic division to form a blastula. These divisions take place
immediately after fertilization. The cells formed by cleavage are called blastomeres.
(2) The type of cleavage in human is holoblastic, i.e. the whole zygote gets divided,
radial and indeterminate, i.e. fate of each blastomere is not predetermined.
(3) Cleavage show faster synthesis of DNA and high consumption of oxygen.
(4) Since there is no growth phase between the cleavages, the size of blastomeres will
be reduced with every successive cleavage
Fig. Stages of cleavage
(5) The cleavages occur as follows :
Cleavage Direction Time Product
(after fertilization)
First IIJ Vertical IIJ 30 hours IIJ 2 blastomeres
Second IIJ Vertical at right IIJ 60 hours IIJ 4 blastomeres
angle to first
Third IIJ Horizontal IIJ 72 hours IIJ 8 blastomeres
(6) Successive divisions produce a solid ball of cells called morula of 16 cells. It
consists of an outer layer of smaller clearer cells and an inner mass of larger cells.
(7) Morula reaches the uterus about 4 – 6 days after fertilization.
Q. 28. Chromosomal aberrations :
(1) The structural, morphological change, which take place in chromosome due to
rearrangement, is called chromosomal aberrations.
(2) The aberrations change the sequence of the genes. This causes variations.
Chromosomal aberrations are mainly of following four types :
(i) Deletion : Loss of genes from chromosome.
(ii) Duplication : Genes are repeated or doubled in number on chromosome,
8 solutions to navneet practice papers : std. xii
(iii) Inversion : A particular segment of chromosome is broken and gets reattached
to the same chromosome in an inverted position due to 180° twist. There is
no loss or gain of gene complement of the chromosome.
(iv) Translocation : Transfer or transposition of a part of chromosome or a set of
genes to a non-homologous chromosome is called translocation. It is effected
naturally by the transposons present in the cell.
Fig. Chromosomal aberrations
Q. 29. (1) The heart is hollow, muscular, conical organ about the size of one’s fist with
broad base and narrow apex tilted towards left measuring about 12 cm in length,
9 cm in breadth and weighing about 250 to 300 grams.
(2) The human heart has four chambers, two atria which are superior, small, thin
walled receiving chambers and two ventricles which are inferior, large, thick
walled, distributing chambers.
(3) Externally there is a transverse groove between the atria and the ventricles which
is known as atrioventricular groove or coronary sulcus.
(4) Between the right and left ventricles there is interventricular sulcus (pl. sulci).In
these sulci the coronary arteries and coronary veins are present.
(5) Oxygenated blood to the heart is supplied by coronary arteries while coronary
veins collect deoxygenated blood from the heart. The coronary veins join to form
coronary sinus which opens into the right atrium.
(6) Right atrium is larger in size than the left atrium. Deoxygenated blood from all
over the body is brought through superior vena cava and inferior vena cava and
poured into right atrium. Oxygenated blood from lungs is brought to heart by two
pairs of pulmonary veins which carry it to the left atrium.
(7) Pulmonary trunk is seen arising from the right ventricle, which carries deoxygenated
blood to lungs. While systemic aorta arises from the left ventricle and carries
oxygenated blood to all parts of the body.
(8) The pulmonary trunk and systemic aorta are connected by ligamentum arteriosum
that represents remnant of ductus arteriosus of foetus.
solutions to navneet practice papers : std. xii 9
Q. 30. 1. Structure of midbrain :
(1) Midbrain is the middle part of the brain situated between the forebrain and the
hindbrain. It is present between the pons varolii and diencephalon.
(2) It has two distinct regions : Corpora quadrigemina and crura cerebri.
(3) Corpora quadrigemina consists of two pairs of lobes, viz., superior colliculi
and inferior colliculi. These are located in the thick wall of midbrain.
(4) Crura cerebri are thick bands of longitudinal nerve fibres, present on the floor
of midbrain.
2. Functions of midbrain :
(1) Inferior colliculi control and coordinate auditory reflexes.
(2) Superior colliculi control head and eye movements.
(3) Crura cerebri connect the cerebrum to cerebellum and spinal cord.
Q. 31. (1) Dairy products prepared using microorganisms are curds, yogurt, butter milk and
cheese.
(2) The starter or inoculum used in preparation of dairy products contains millions of
lactic acid bacteria (LaB).
(3) Curd is prepared by inoculating milk with Lactobacillus acidophilus. It ferments
lactose sugar of milk into lactic acid. Lactic acid causes coagulation and partial
digestion of milk protein casein. Thus, milk is changed into curd. It also checks
growth of disease causing microbes.
(4) Yogurt is produced by curdling milk with the help of Streptococcus thermophilus
and Lactobacillus bulgaricus.
(5) Buttermilk is the acidulated liquid left after churning of butter from curd, is called
buttermilk.
(6) During the preparation of cheese, the milk is coagulated with lactic acid bacteria.
The curd formed is filtered and whey is separated. The solid mass is then ripened
with growth of mould that develops flavour in it. Characteristic texture, flavour
and taste of cheese are developed by different specific microbes. The ‘roquefort
cheese is ripened by bluegreen mold Penicillium roquefortii. Camembert cheese
is ripened by blue-green mold P. camembertii. The large holes in Swiss cheese
are developed due to production of a large amount of CO2 by a bacterium known
as Propionibacterium shermanii.
————
10 solutions to navneet practice papers : std. xii
