Maharashtra Board Class 12 Biology Sample Paper Set 2 with Solutions

Maharashtra State Board Class 12th Biology Sample Paper Set 2 with Solutions Answers Pdf Download.

Maharashtra Board Class 12 Biology Model Paper Set 2 with Solutions

Section A

Question 1.
Select and write the correct answers to the following questions:

(i) Which one of the following diseases is non – communicable?
(a) Diphtheria
(b) Flu
(c) Cancer
(d) Malaria
Answer:
(c) Cancer

(ii) Chromosomal theory of inheritance was proposed by …..
(a) Watson and Crick
(b) Sutton and Boveri
(c) Mendel
(d) T.H. Morgan
Answer:
(b) Sutton and Boveri

(iii) Genes involved in cancer are ………
(a) Tumour genes
(b) Regulator genes
(c) Oncogenes
(d) Complementary genes
Answer:
(c) Oncogenes

(iv) Restriction enzymes were discovered by ……..
(a) Smith and Nathans
(b) Alexander Fleming
(c) Berg
(d) None
Answer:
(a) Smith and Nathans

(v) Which statement is correct with respect to the food chain?
(a) Every component of food chain forms trophic level
(b) Inter-relation between different food chains is known as a food web.
(c) All the chains formed by nutritional relations is used to understand energy flow.
(d) All of the above.
Answer:
(d) All of the above

(vi) The PCR technique is used for ……….
(a) Gene sequencing
(b) Gene cloning
(c) Gene splicing
(d) Gene expression
Answer:
(b) Gene cloning

(vii) Lesser variation in biomass production over a period of time is called …….
(a) Productivity Stability Hypothesis
(b) Species Area Relationship
(c) Species Life Cycle
(d) None of them
Answer:
(a) Productivity Stability Hypothesis

(viii) The species placed in CR category is ………
(a) Endangered
(b) Critically Endangered
(c) Vulnerable
(d) Not Evaluated
Answer:
(b) Critically Endangered

(ix) To control emission of ozone depleting substances International Treaty was signed in 1987.
(a) Kyoto Protocol
(b) Ramsar Convention
(c) Montreal Protocol
(d) Bonn Convention
Answer:
(c) Montreal protocol

(x) Which of the following requires maximum energy?
(a) Secondary consumer
(b) Decomposer
(c) Primary consumer
(d) Primary producer
Answer:
(d) Primary producer

Question 2.
Answer the following questions:

(i) Name two better yielding varieties of rice developed in India.
Answer:
Jaya, Padma, Ratna.

(ii) What is Dead Space?
Answer:
The volume of air that is present in the respiratory tract (from nose to the terminal bronchioles), but not involved in gaseous exchange. It is 150 ml.

(iii) What is guttation?
Answer:
The Loss of water in the form of liquid through water stomata or hydathodes of some vascular plants like grasses.

(iv) Who isolated Gibberellins first?
Answer:
Kurosawa, a Japanese scientist first isolated Gibberellins from the fungus Gibberella fujikuroi in 1926.

(v) How malarial parasite plasmodium is transmitted from person to person?
Answer:
The malarial parasite Plasmodium is transmitted through an insect vector – female Anopheles mosquito.

(vi) Define Serology.
Answer:
Study of antigen- antibody interaction is called serology.

(vii) Name any two X-linked recessive disorders.
Answer:

1. Colour blindness: Person unable to distinguish between red and green colours.
2. Haemophilia (Bleeder’s disease): Blood fails to clot or coagulates very slowly.

(viii) Define the following terms:
(a) Parasitism
(b) Niche
Answer:
(a) Parasitism: Parasitism is the association between two organisms in which one organism is benefitted and another organism is harmed.

(b) Niche: A niche is a term that defines an organisms’s role in an ecosystem.

Section – B

Attempt any Eight of the following questions:

Question 3.
Name thyroid hormones and give their functions.
Answer:
Thyroid gland secrets two hormones:

1. Thyroxine (T₄)
2. Triiodothyronine (T₃)

Functions of thyroid hormones:

(a) Regulates basal metabolic rate of the body.
(b) Promotes growth of the body by stimulating protein synthesis.
(c) Regulates the body temperature.
(d) Maintains water and electrolyte balance.

Question 4.
Give adaptations in anemophilous flowers.
Answer:

1. The flowers are small in size, colourless and inconspicuous.
2. The flowers lack nectar and fragrance.
3. The anthers are large with long filaments.
4. The pollen grains are light in weight, dry and produced in large numbers.
5. Stigma is feathery to trap pollen grains.
6. Stamens and stigmas are exposed to air current.

Question 5.
Write a note on IVF.
Answer:

1. In Vitro Fertilisation (IVF) is a process by which an egg is fertilised by sperm outside the body in a test tube or glass plate to form a zygote in the laboratory.
2. The process involves monitoring and stimulating a woman’s ovulatory process, removing ovum or ova from the woman’s ovaries and letting sperm fertilise them in a fluid medium in a laboratory.
3. The zygote or early embryos are then transferred into the fallopian tube for further development.

Question 6.
Enlist the four characteristics of genetic code.
Answer:

1. Triplet nature: Sequence of three nucleotide bases constitute a codon which defines one particular amino acid.
2. Distinct polarity: Genetic code is always read in 5′ → 3′ direction as it shows definite polarity.
3. Genetic code is commaless: There are no commas between the codons.
4. Degeneracy: Generally single amino acid is encoded by single codon but some amino acids are encoded by more than one codon.
5. Genetic code is universal: All living organisms have the same genetic code. The specific codon specifies same amino acid in all living organisms.

Question 7.
What is transpiration ? Explain role of transpiration.
Answer:
Transpiration is the Ipss of water in the form of vapour from plants. Transpiration occurs through leaves.
Role of transpiration:

1. It helps to transport water and minerals towards the leaves from the roots.
2. It cools down the plant during summer.
3. It removes excess water.

Question 8.
Give economic importance of fishery.
Answer:

1. Fishes are the source of nutritious food.
2. Fish yield by-products like fish oil, fish meal, fertilizers, fish guano, fish glue and isinglass.
3. These by-products are used in paints, soaps, oils and medicines.
4. Fishery provides good job opportunities and self-employment.

Question 9.
Draw a diagram of pyramid of energy.
Answer:

Question 10.
Distinguish between Artery and Vein.
Answer:

Artery	Vein
Transport blood away from the heart.	Transport blood to the heart.
Usually situated deeper in the body.	Usually situated beneath the surface of the skin.
Carry oxygenated blood except the pulmonary artery.	Carry deoxygenated blood except the pulmonary vein.
Blood flows through arteries rapidly and with high pressure.	Blood flows through veins slowly and with Low pressure.
Internal valves are not present.	Internal valves are present.

Question 11.
Give main features of mutation theory.
Answer:
Mutation theory was proposed by Hugo de Vries in 1901.
The main features of mutation theory are:

1. Mutations are large and discontinuous variations.
2. Mutations appear all of a sudden.
3. Mutations are the row material for organic evolution.
4. All mutations are inheritable.
5. Mutation may be useful or harmful.
6. Useful mutations are selected by nature.

Question 12.
Write a short note on ‘Greenhouse effect’.
Answer:

1. Greenhouse effect is a naturally occurring phenomenon that is responsible for heating of earth’s surface and atmosphere.
2. Due to greenhouse effect the average temperature’ of the Earth is 15°C instead of-18°C.
3. Clouds and gases reflect about 1/4 of the solar radiations that reaches earth and absorb some of it.
4. About half of total incoming radiations reach the earth’s surface and heat it. Earths surface re-emits heat in the form of infrared radiations but a part of these radiations does not escape into the space because CO₂, CH₄ gases absorb a major portion.
5. The molecules of these gases radiate the absorbed heat energy and a major part of it comes back to earth’s surface thus heating it up once again. This cycle is repeated again and again.

Question 13.
Explain the properties of a ideal cloning vector in r-DNA technology.
Answer:

1. It must be small in size.
2. It should be easily introduced into host cells.
3. It should have ability of independent replication.
4. It should have marker genes for antibiotic resistance.
5. It must possess multiple cloning site.
6. It must contain restriction site for restriction endonucleases.

Question 14.
Give reason – Injury to medulla oblongata may prove fatal.
Answer:

1. The medulla oblongata is the posterior part of brain, located in brain stem. It continues as spinal cord.
2. It controls involuntary vital activities like heart beat, respiration, breathing, circulation, peristalsis, the function of blood vessels etc.
3. Injury to medulla may stop all these vital activities and this can cause death.

Section – C

Attempt any Eight of the following questions:

Question 15.
Describe the structure of human sperm.
Answer:

1. Human sperm is divisible into three parts – head, middle piece and tail.
   
2. Head: The head of sperm is oval. It contains haploid nucleus. Above the nucleus cap like acrosome is present. It contains hydrolytic enzymes like hyaluronidase, zona lysins and corona penetrating enzymes.
3. Neck: Very short region having two centrioles i.e., proximal centriole and distal centriole.
4. Middle piece: It possesses 10-14 spiral turns of mitocondria, which produce energy forthe movement of the sperm.
5. Tail: It is thin, long with tapering end and contains cytoplasm and axial filament. The part of tail without plasma membrane is called end piece. Tail helps the sperm cell to swim to reach the ovum.

Question 16.
What is nitrification? Name any two nitrifying bacteria in soil.
Answer:
Nitrification is the process of conversion of ammonia into nitrites.
It involves two steps:

1. Ammonium ions are oxidized into nitrates by the bacteria like Nitrosomonas and Nitrosococcus.
2. Nitrites are converted into nitrates by the bacteria like Nitrobacter.

Question 17.
Explain the process of blood clotting.
Answer:

1. Blood clotting is also known as blood coagulation. It is a process in which the liquid blood changes into a semi solid form known as clot.
2. The process of blood clotting prevents the excessive loss of blood.
3. The process of blood clotting occurs in a series of following steps:
   • The injured tissue cells and the platelets (thrombocytes) release thromboplastin.
   • Thromboplastin helps in the formation of enzyme prothrombinase in presence of Ca²⁺ ions.
   • Prothombinase inactivates heparin (anticoagulant) and also converts inactive prothrombin into active thrombin.
   • Thrombin converts soluble fibrinogen into insoluble fibrin in the presence of Ca²⁺ ions.
   • Fibrin forms a mesh or network in which platelets (thrombocytes) and other blood cells get trapped to form the clot.

Question 18.
Define ornithophily and enlist adaptations in ornithophilous flowers.
Answer:
Ornithophily is bird pollination, where the pollen grains of the flower are distributed by the specialised birds for pollination. They usually have long beaks and are small in size, e.g., sun birds, humming birds, Bombax, Callistemon (bottle brush) etc.

Adapation for the pollination in ornithophilous flower:

1. Flowers are usually brightly coloured, large and showy.
2. They secrete profuse, dilute nectar.
3. Pollen grains are sticky and spiny.
4. Flowers are generally without fragrance, as birds have poor sense of smell.

Question 19.
Give name, type and origin of following cranial nerves:
Number-II, Number-IV, Number-IX
Answer:

Number	Name	Type	Origin
II	Optic	Sensory	Side of diencephalon
IV	Pathetic	Motor	Floor of mid­brain
IX	Glossopharyn­-geal	Mixed	Side of Medulla oblongata

Question 20.
What are transgenic animals? Explain any four ways in which such animals can be beneficial for humans.
Answer:
Animals that have their DNA manipulated to possess and express foreign gene are called transgenic animals. Examples of transgenic animals are mice, rats, rabbits, pigs, sheep, cows and fish.

Uses of transgenic animals for humans are:

1. To study gene regulation, their effect on the normal functions of the body and its development.
2. Study of genes, which are responsible for diseases in human and their treatment, e.g. cancer,
3. Useful biological products can be produced by introducing the portion of DNA, which codes for a particular product into transgenic animals.
4. Transgenic mice are used to test the safety of vaccines before being used in humans.

Question 21.
Write a note on significance of Palaeontology.
Answer:

1. It is useful to understand and reconstruct evolutionary history (Phylogeny).
2. It gives us idea about various forms and structure of extinct organisms.
3. It provides record of connecting link between two groups of organisms.
4. It helps to reconstruct palaeoecology, palaeoenvironment of a selected area.
5. It helps in study of habits of extinct organisms.

Question 22.
What are long day plants (LDP)? Give two examples.
Answer:

1. The plants that flower only when amount of day light is longer than their critical photopheriod.
2. These plants flower during summer.
3. These plants are called short night plants as they require short dark period.
4. These plants require more than 14 hours of day light. Example:
   • Spinach
   • Pea
   • Cabbage
   • Radish

Question 23.
Sketch and label Human Male Reproductive System. Write briefly about the Testis.
Answer:

The testis is externally covered by a collagenous connective tissue layer called tunica albuginea. Outer to it is an incomplete peritoneal covering called tunica vaginalis, and inner to it is tunica vasculosa, a thin membranous and vascular layer.

Fibers from tunica albuginea divide each testis into about 200-300 testicular lobules, each with 1-4 highly coiled seminiferous tubules. Each seminiferous tubule is internally lined by cuboidal germinal epithelial cells (spermatogonia) and few large pyramidal cells called Sertoli or sustentacular cells.

The germinal epithelial cells undergo gametogenesis to form the spermatozoa. Sertoli cells provide nutrition to the developing sperms. Various stages of spermatogenesis can be seen in the seminiferous tubules. The inner most spermatogonial cell (2n), primary spermatocyte (2n), secondary spermatocyte (n), spermatids (n) and sperms (n). The Interstitial or Leydig’s cells lie in between the seminiferous tubules. They secrete the male hormone androgen or testosterone.

Question 24.
Sketch and label Anatropous ovule.
Answer:

Question 25.
Describe the term Niche.
Answer:

1. The term niche was coined by J. Grinnell in 1917.
2. Niche not only describes the position of a species in an environment but also describes the functional role played by an organism.
3. Niche is specific to each species and no two species can share the same niche.
4. It includes various aspects of the life of an organism like food, shelter etc.
5. Niche deals with the flow of energy from one organism to another.
6. There are three types of niche:
   • Spatial niche
   • Trophic niche
   • Multi- dimensional niche.
7. Organisms living in same habitat differ in their niches because of different eating habits.

Question 26.
Match the following pairs:

Column A Antibiotic produced	Column B Microbial source
(i) Penicillin	(a) Streptomyces venezuelae
(i) Chloromycetin	(b) Bacillus licheniformis
(ii) Bocitrocin	(c) Streptomyces aurifaciens
(iii) Erythromycin	(d) Streptomyces griseus
(iv) Streptomycin	(e) Penicillium chrysogenum
(v) Terromycin	(f) Streptomyces erythreus

Answer:

Column A	Column B
(ï) Penicillin	Penicillium chrysogenum
(ii) Chloromjcetn	Streptomyces venezuelae
(iii) Bocitracin	Bacillus ticheniformis
(iv) Erjthromycin	Streptomyces erythreus
(v) Streptomcin	Streptomyces griseus
(vi) Terramycin	Streptomyces aurifaciens

Section – D

Attempt any Three of the following questions:

Question 27.
Describe the conducting system of human heart.
Answer:

1. The human heart is myogenic i.e., it is capable of generating a cardiac contraction by a specialised conducting (nodal) tissue.
2. The conducting (nodal) tissue consists of SA node or sino-atrial node, AV node or atrio-ventricular node, bundle of His and Purkinje fibres.
3. SA node is present in right atrium near the opening of the superior vena cava.
4. SA node generates wave of contraction and passes the wave of contraction to the AV node and the left ventricle.
5. AV node is present in the right atrial wall near the base of interatrial septum and near the opening of the coronary sinus. The AV node passes the wave of contraction to both the ventricles.
6. Bundle of His branches start from AV node and pass through interventricular septum. It forms two branches one for each ventricle.
7. These branches form network in the walls of both ventricles. The fibres of these branches are called Purkinje fibres.
8. Bundle of His and Purkinje fibres transmit the wave of contraction in both the ventricles.

Question 28.
Read the following functions carefully and write the names of hormones and the glands secreting them:

(i) Controls calcium level in the blood.
(ii) Basal metabolic rate.
(iii) Maturation of Graafian follicle.
(iv) Stimulates intestinal glands to secrete intestinal juice.
(v) Heart beat and blood pressure.
(vi) Secretion of growth hormone.
(vii) Uterine contraction.
(viii) Controls tubular absorption of water in kidneys.
Answer:

Function	Hormone	Gland
(i) Controls calcium level in the blood	Parathormone (PTH)	Parathy­roid gland
(ii) Basal Metabolic rate	Thyroxine	Thyroid gland
(iii) Maturation of Graafian follicle	Follicle stimu­lating hormone (FSH)	Pituitary gland
(iv) Stimulates gastric glands to produce gastric juice	Gastrin	G-cells
(v) Heart beat and blood pressure	Thyroxine	Thyroid gland
(vi) Secretion of growth hormone	Growth hormone releasing hormone	Hypothal­amus
(vii) Uterine contraction	Oxytocin	Pituitary gland
(viii) Controls tubular absorption of water in kidneys	Antidiuretic hormone or vasopressin	Pituitary gland

Question 29.
Explain the process of transcription in protein synthesis.
Answer:

1. Transcription is the first step of protein synthesis. It takes place in the nucleus of the cell.
2. In transcription the information of only one strand of DNA is copied into a molecule of messanger RNA (mRNA).
3. DNA has promoter and terminator site, transcription starts at promoter site and stops at terminator site.
4. The m-RNA synthesized in transcription is complementary to a strand of DNA.
5. Transcription takes place in three steps:

(a) Initiation
(b) Elongation
(c) Termination

(a) Initiation: It is the beginning of transcription. The enzyme RNA polymerase binds to a promoter site. After binding to promoter, RNA polymerase moves along the DNA and causes local unwinding of DNA so the enzyme can read the bases of template strand.

(b) Elongation: It is the addition of nucleotides to the mRNA strand. RNA polymerase reads the template DNA strand and adds complementary base pairs.

(c) Termination: It is the end of transcription. When RNA polymerase reaches the termination site of DNA, it leaves DNA and fully formed mRNA.

Question 30.
Describe the different types of chromosomes.
Answer:
There are four main types of chromosomes depending upon the position of centromere:

(i) Acrocentric
(ii) Telocentric
(iii) Submetacentric
(iv) Metacentric

(i) Acrocentric:
(a) The centromere is near one end of the chromosome.
(b) Short chromosomal arm is present.
(c) The chromosome appears ‘j’ shaped.

(ii) Telocentric:
(a) The centromere is at one end.
(b) There is only one chromosomal arm.
(c) Appears ‘i shaped.

(iii) Submetacentric:
(a) The centromere is located near the middle.
(b) The chromosomal arms are slightly unequal in length.
(c) Appears ‘L’ shaped.

(iv) Metacentric:
(a) The centromere is located in the middle.
(b) The chromosomal arms are almost equal.
(c) Appears ‘V’ shaped.

Question 31.
Explain movement of water in root.
Answer:

1. Water is absorbed by root hair cell through the processes like imbibition, diffusion, osmosis which occur sequentially.
2. Water passes through epidermal cell (epiblema), cortex, endodermis, casparian strip, pericycle and then to protoxylem.
3. When root hair cell absorbs water it becomes turgid. Its turgor pressure increases, but its DPD (Diffusion Pressure Deficit) value decreases. However, the immediately adjacent cortical cell inner to it, has more DPD value, because its O. P. is more.
4. Therefore, cortical cell will absorb water from the turgid root hair cell. It then becomes turgid. The flaccid root hair cell now absorbs water from soil.
5. Water from the turgid cortical cell is absorbed by inner cortical cell and the process goes on. Thus, a gradient of suction pressure (DPD) is developed from cells of epiblema to the cortex of the root.
6. Consequently water moves rapidly across the root through loosely arranged living cells of cortex, followed by passage cells of endodermis and finally into the cell of pericycle.
7. Protoxylem is in the close proximity with pericycle.
8. It is due to root pressure, water from pericycle is forced into the xylem.
9. Pathway of water across the root occurs in two types: Apoplast pathway and Symplast pathway.

Maharashtra Board Class 12 Biology Previous Year Question Papers