Showing posts with label HSC Biology. Show all posts
Showing posts with label HSC Biology. Show all posts

Maharashtra Board Class 12 Biology Question Paper Solutions July 2019

Biology

Board Question Paper : July 2019 Solutions

SECTION – A
Q.1.
_______ drug is used for patients who have undergone surgery.
  • (A) Marijuana
  • (B) Smack
  • (C) Morphine
  • (D) Cannabinoids
Answer: (C) Morphine
Q.2.
Name the process by which all the three types of non-genetic RNAs are produced on DNA template.
  • (A) Translation
  • (B) Transcription
  • (C) Termination
  • (D) Replication
Answer: (B) Transcription
Q.3.
Which of the animal groups show uricotelism?
  • (A) Snake, rat, terrestrial insect
  • (B) Penguin, reptile, snail
  • (C) Land snail, bird, lizard
  • (D) Tadpole larva of frog, marine fish, spider
Answer: (C) Land snail, bird, lizard
Q.4.
Approximately how many eggs are produced by a normal healthy human female up to the age of 25 years if the age of menarche is 12 years _______.
  • (A) 169
  • (B) 416
  • (C) 240
  • (D) 100
Answer: (A) 169
Calculation: (25 years - 12 years) = 13 reproductive years. 13 years × 13 eggs/year = 169 eggs.
Q.5.
Name the process in which a tumour successfully spreads to the other parts of the body, grows and destroys healthy tissues.
Answer: Metastasis
Q.6.
What is humification?
Answer: Humification is the process of decomposition of detritus to form a dark coloured, amorphous, colloidal substance called humus. It is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
Q.7.
Name the sexually transmitted disease caused by Treponema pallidum.
Answer: Syphilis
Q.8.
Which is the process that removes introns from RNA?
Answer: Splicing (or RNA Splicing)

HSC Biology

SECTION – B
Q.9.
Define fermentation. Write the names of substrate of alcoholic and lactic acid fermentation.
Answer: Definition: Fermentation is the anaerobic breakdown of glucose or other organic nutrients into simpler compounds like alcohol or lactic acid along with the release of a small amount of energy.

Substrate: The primary substrate for both alcoholic and lactic acid fermentation is Glucose.
Q.10.
Complete the following chart and rewrite it:
Genotype Phenotype
\(I^A I^A\) or \(I^A i\) Blood Group A
\(I^B I^B\) or \(I^B i\) B
\(I^A I^B\) Blood Group AB
ii O
Answer: The completed chart is filled above in bold.
Q.11.
Your friend wants to start a business of Apiculture. Enlist the equipment he would need.
Answer: Equipment needed for Apiculture includes:
  • Bee hive (Artificial wooden box) with frames and foundation sheets
  • Hive stand
  • Smoker (to calm bees)
  • Bee veil / Protective clothing (gloves, overall)
  • Queen Excluder
  • Honey Extractor
  • Uncapping knife
  • Brush
Q.12.
Give the role of:
i. Tissue plasminogen activator (TPA)
ii. Tissue growth factor-Beta (TGF-β) in Gene therapy.
Answer: i. Tissue plasminogen activator (TPA): It is an enzyme used as a thrombolytic agent (clot buster) to dissolve blood clots in blood vessels, useful in treating heart attacks and strokes.
ii. Tissue growth factor-Beta (TGF-β): It is used to stimulate cell growth, new blood vessel formation (angiogenesis), and promotes wound healing and tissue repair.
Q.13.
Match the following and rewrite it:
Answer:
  • i. Invertase — b. Saccharomyces cerevisiae
  • ii. Lipase — d. Rhizopus spp. (or Candida)
  • iii. Cellulase — a. Trichoderma konigi
  • iv. Pectinase — c. Sclerotinia libertinia
Q.14.
Sketch and label hairpin model of tRNA.
Diagram of Hairpin model of tRNA
(Diagram should show the Clover leaf structure with: 3' Acceptor arm with CCA end, 5' end, TΨC loop, DHU loop, Anticodon loop with anticodon triplet, and Variable arm.)
Answer: See diagram description above.
Q.15.
Identify and write the names of given diagrams A, B, C and D.
Identify and write the names of given diagrams A, B, C and D. [Image References from Question Paper]
Answer: A: Eosinophil (Acidophil)
B: Neutrophil
C: Lymphocyte
D: Monocyte
OR
Dilip and Mohsin measured their blood pressure. Dilip’s B.P. is 120/80 mmHg and Mohsin’s B.P. is 160/100 mmHg. Who is suffering from hypertension? What are its causes?
Answer: Who is suffering: Mohsin is suffering from hypertension (High Blood Pressure).
Causes: Stress, obesity, high dietary salt intake, smoking, alcoholism, arteriosclerosis (hardening of arteries), kidney disorders, or genetic factors.
Q.16.
Give the functions of Kidney.
Answer: Functions of Kidney:
  1. Excretion: Removal of nitrogenous metabolic wastes like urea and uric acid.
  2. Osmoregulation: Maintenance of water and salt balance (homeostasis) in the body.
  3. pH Regulation: Maintaining the acid-base balance of blood.
  4. Secretion: Produces hormones like Erythropoietin (for RBC formation) and Renin (for BP regulation).
Q.17.
Give the location of following valves within human heart:
i. Eustachian valve
ii. Thebesian valve
iii. Bicuspid valve
iv. Tricuspid valve
Answer: i. Eustachian valve: Guards the opening of the Inferior Vena Cava in the Right Atrium.
ii. Thebesian valve: Guards the opening of the Coronary Sinus in the Right Atrium.
iii. Bicuspid (Mitral) valve: Located between the Left Atrium and Left Ventricle.
iv. Tricuspid valve: Located between the Right Atrium and Right Ventricle.
Q.18.
Define Green House Gases. Give any two examples.
Answer: Definition: Greenhouse gases are atmospheric gases that absorb infrared radiation (heat) emitted from the Earth's surface and re-radiate it back, trapping heat in the atmosphere and causing the greenhouse effect.
Examples: Carbon dioxide (\(CO_2\)), Methane (\(CH_4\)), Chlorofluorocarbons (CFCs), Nitrous oxide (\(N_2O\)).
SECTION – C
Q.19.
Explain Homologous and Analogous organs with example.
Answer: 1. Homologous Organs:
  • Organs that have the same fundamental structure and embryonic origin but perform different functions.
  • They indicate divergent evolution and common ancestry.
  • Example: Forelimbs of Human (for grasping), Whale (for swimming), Bat (for flying), and Cheetah (for running). All share the same bone structure (humerus, radius, ulna, etc.) but differ in function.
2. Analogous Organs:
  • Organs that have different structural details and embryonic origins but perform the same function.
  • They indicate convergent evolution.
  • Example: Wings of a Butterfly (chitinous membrane) and Wings of a Bird (feathers and bones). Both are used for flight but are structurally different.
Q.20.
A homozygous tall pea plant is crossed with its homozygous recessive parent. Find out the genotypic and phenotypic ratio with the help of Punnet square method.
Answer: Parents: Homozygous Tall (TT) × Homozygous Dwarf (tt)
Gametes: (T) and (t)

Punnett Square (F1 Generation):
♂ \ ♀ t t
T Tt (Tall) Tt (Tall)
T Tt (Tall) Tt (Tall)

F1 Result: All offspring are Heterozygous Tall (Tt).
(Note: If the question implies finding the F2 ratio by selfing the F1 generation, which is standard for such questions):
Selfing F1 (Tt × Tt):
F2 Phenotypic Ratio: 3 Tall : 1 Dwarf
F2 Genotypic Ratio: 1 Homozygous Tall (TT) : 2 Heterozygous Tall (Tt) : 1 Homozygous Dwarf (tt)
Q.21.
Sketch and label the structure of Malpighian body and explain the structure of Bowman’s capsule.
Diagram of Malpighian Body
(Diagram should show: Afferent arteriole, Efferent arteriole, Glomerulus (capillary knot), Bowman’s capsule (Cup shape), Parietal layer, Visceral layer, Capsular space, and PCT.)
Answer: Structure of Bowman’s Capsule:
  • It is a double-walled, cup-shaped structure located at the beginning of the nephron.
  • It consists of an outer Parietal layer composed of simple squamous epithelium and an inner Visceral layer composed of specialized cells called Podocytes.
  • Podocytes have foot-like processes (pedicels) that wrap around glomerular capillaries, leaving slit pores for filtration.
  • The space between the two layers is called the Capsular space or urinary space, which receives the glomerular filtrate.
Q.22.
Write down the names of missing intermediate compounds in a sequence in the given diagrammatic representation of Kreb’s cycle.
Kreb’s cycle. [Image References from Question Paper]
Answer: Based on the sequence of Kreb's cycle:
  1. Acetyl Co-A (Enters the cycle to combine with Oxaloacetate)
  2. Oxaloacetate (Combines with Acetyl Co-A to form Citrate)
  3. Oxalosuccinate (Intermediate between Isocitrate and \(\alpha\)-Ketoglutarate)
  4. Succinyl Co-A (Formed from \(\alpha\)-Ketoglutarate)
  5. Succinate (Formed from Succinyl Co-A)
  6. Malate (Formed from Fumarate)
Q.23.
Define jumping genes. Classify them on the basis of their mechanism.
Answer: Definition: Jumping genes, or Transposons, are DNA sequences that have the ability to move (transpose) from one location to another within the genome.

Classification based on mechanism:
  1. Retrotransposons (Class I): They move via a "copy and paste" mechanism. The DNA is transcribed into RNA, and then reverse-transcribed back into DNA which is inserted at a new location.
  2. DNA Transposons (Class II): They move via a "cut and paste" mechanism. The DNA segment is excised from its original position and inserted directly into a new location.
Q.24.
Identify A, B, C in the given diagram and give their functions.
Identify A, B, C in the given diagram and give their functions [Image References from Question Paper]
Answer: A: Acrosome - It contains hydrolytic enzymes (hyaluronidase) that help the sperm penetrate the egg during fertilization.
B: Mitochondria (Nebenkern) / Middle Piece - It provides energy (ATP) for the movement of the sperm.
C: Tail (Flagellum) - It provides motility to the sperm, allowing it to swim towards the ovum.
OR
Explain various mechanical methods of birth control.
Answer: Mechanical methods (Barrier methods) prevent the physical meeting of sperm and ovum:
  • Condom (Nirodh): A rubber/latex sheath worn over the penis (male) or inside the vagina (female) to collect semen and prevent it from entering the uterus. It also protects against STDs.
  • Diaphragm / Cervical Cap: Rubber domes inserted into the female reproductive tract to cover the cervix, blocking sperm entry.
  • Intrauterine Devices (IUDs): Devices like Lippes loop, Cu-T, or Multiload 375 inserted into the uterus. They increase phagocytosis of sperm and suppress sperm motility/fertilizing capacity. (Sometimes classified separately, but mechanically block implantation).
Q.25.
Identify disorders developed in the given genotypes and give two symptoms of each:
i. 44 + XO
ii. 44 + XXY
Answer: i. Genotype 44 + XO: Turner’s Syndrome
Symptoms:
  • Sterile female with rudimentary ovaries.
  • Short stature, webbed neck, and shield-shaped chest.

ii. Genotype 44 + XXY: Klinefelter’s Syndrome
Symptoms:
  • Sterile male with under-developed testes (Hypogonadism).
  • Development of breast in males (Gynecomastia) and sparse body hair.
Q.26.
Name the interaction in:
i. Lichen
ii. Sucker fish and shark
iii. A protozoan living in the digestive tract of a flea living on a dog.
Answer: i. Lichen: Mutualism (Symbiotic relationship between Algae and Fungi).
ii. Sucker fish and Shark: Commensalism (Sucker fish benefits from transport/food, Shark is unaffected).
iii. Protozoan in flea on dog: Hyperparasitism (The protozoan is a parasite of the flea, which is itself a parasite of the dog).
Q.27.
Given an account of various steps involved in tissue culture.
Answer: The steps involved in tissue culture are:
  1. Explant Selection: Selecting a healthy plant part (shoot tip, leaf, etc.) to be cultured.
  2. Sterilization: Sterilizing the glassware, nutrient medium, and surface sterilization of the explant to prevent microbial contamination.
  3. Inoculation: Transferring the explant onto the nutrient medium in aseptic conditions (Laminar air flow).
  4. Incubation: Keeping the culture in a controlled environment (light, temperature, humidity) to allow growth.
  5. Callus Formation: The explant cells divide to form an undifferentiated mass of cells called Callus.
  6. Organogenesis: Differentiation of callus into roots and shoots by altering the ratio of hormones (Auxins and Cytokinins).
  7. Hardening: Gradual acclimatization of plantlets to the natural environment.
  8. Transfer: Planting the hardened plantlets in the field.
SECTION – D
Q.28.
Give the diagrammatic representation of HSK-pathway and answer the following questions:
i. Why is photorespiration avoided in C4 pathways?
ii. Give any two examples of C4 plants.
iii. Name the CO2 acceptor in mesophyll cells during HSK pathway.
Diagram of HSK Pathway
(Diagram should show Mesophyll cell and Bundle Sheath cell interaction: CO2 fixed by PEP to OAA -> Malate -> Transport to BS cell -> Decarboxylation to release CO2 -> Calvin Cycle -> Pyruvate -> Transport back to Mesophyll -> Regeneration of PEP.)
Answer: i. Avoidance of Photorespiration: In C4 plants, the enzyme RuBisCO is present only in the bundle sheath cells. The C4 mechanism concentrates \(CO_2\) in these cells (by decarboxylation of malate), ensuring a high \(CO_2\) to \(O_2\) ratio. This prevents RuBisCO from acting as an oxygenase, thus avoiding photorespiration.
ii. Examples: Maize (Corn), Sugarcane, Sorghum.
iii. CO2 Acceptor: Phosphoenolpyruvate (PEP).
OR
Identify and explain with the help of diagrammatic representation, type of photophosphorylation in which P700 (PS II) and P680 (PS I) both are involved.
Answer: Identification: The process involves both Photosystem II (P680) and Photosystem I (P700), so it is Non-Cyclic Photophosphorylation (Z-Scheme).

Explanation:
  • Light hits PS II (P680), exciting electrons which are accepted by a primary acceptor.
  • Electrons flow down an electron transport chain (Plastoquinone -> Cytochrome b6f -> Plastocyanin) to PS I.
  • During this flow, ATP is synthesized from ADP + Pi.
  • Simultaneously, photolysis of water occurs at PS II to replace lost electrons, releasing \(O_2\).
  • Light hits PS I (P700), exciting electrons which reduce NADP+ to NADPH via Ferredoxin.
  • Result: Synthesis of ATP and NADPH, and release of Oxygen.
Q.29.
Give reasons:
i. Pituitary gland was formerly called as ‘master endocrine gland’.
ii. Oxytocin is ‘birth hormone’.
iii. People living in hilly region are advised to use iodised salt.
iv. Old age persons show weakened immune response.
v. Pancreas is a dual gland.
Answer: i. The Pituitary gland secretes hormones that control and regulate the secretions of many other endocrine glands (like Thyroid, Adrenal cortex, Gonads). Hence, it was called the master gland (though it is itself controlled by the Hypothalamus).
ii. Oxytocin stimulates vigorous contraction of the smooth muscles of the uterus at the end of pregnancy, causing expulsion of the fetus (parturition). Hence, it is called the birth hormone.
iii. The soil in hilly regions is often deficient in iodine, leading to iodine-deficient food. Iodine is essential for Thyroxine synthesis. To prevent Goiter (thyroid enlargement) caused by this deficiency, iodised salt is advised.
iv. The Thymus gland, which acts as a training school for T-lymphocytes, degenerates with age. This leads to a decrease in the production of T-cells and cell-mediated immunity, causing a weakened immune response in old age.
v. Pancreas acts as both an exocrine gland (secreting digestive enzymes like trypsin, lipase via ducts) and an endocrine gland (Islets of Langerhans secreting hormones Insulin and Glucagon into the blood). Hence, it is a dual (heterocrine) gland.
OR
Describe functional areas of cerebrum with the help of neat and labelled diagram.
Answer: Functional Areas of Cerebrum:
  • Frontal Lobe: Contains the Motor area (controls voluntary movements), Broca’s area (motor speech area), and areas for intellect, memory, and will-power.
  • Parietal Lobe: Contains the Somatosensory area (perception of touch, pain, pressure, temperature, taste).
  • Temporal Lobe: Contains the Auditory area (hearing), Olfactory area (smell), and Wernicke’s area (understanding speech).
  • Occipital Lobe: Contains the Visual area (sight/vision).
Lateral view of Human Brain showing lobes and functional areas [Image: Diagram of Lateral view of Human Brain showing lobes and functional areas]
Q.30.
Define pollination. Explain different types of self and cross pollination with suitable examples.
Answer: Definition: Pollination is the transfer of pollen grains from the anther to the stigma of the same or a different flower.

1. Self Pollination: Transfer of pollen to the stigma of the same flower or another flower on the same plant.
  • Autogamy: Pollination within the same flower. E.g., Pea.
  • Geitonogamy: Pollination between different flowers of the same plant. E.g., Cucurbits.
2. Cross Pollination (Xenogamy/Allogamy): Transfer of pollen to the stigma of a flower on a different plant of the same species. It requires external agents.
  • Anemophily (Wind): E.g., Maize, Wheat.
  • Hydrophily (Water): E.g., Vallisneria, Zostera.
  • Entomophily (Insects): E.g., Rose, Jasmine.
  • Ornithophily (Birds): E.g., Butea, Bombax.
OR
Sketch and label the V.S. of anatropous ovule and answer the following questions:
i. How many mitotic divisions are required to produce embryo sac?
ii. Which part of ovule is converted into seed coat?
iii. Which part provides the passage for entry of pollen tube during fertilization?
Diagram of V.S. of Anatropous Ovule
(Diagram of Inverted ovule showing Funiculus, Hilum, Outer/Inner Integuments, Micropyle, Nucellus, Chalaza, and Embryo Sac with Egg apparatus, Polar nuclei, Antipodals.)
Answer: i. Mitotic Divisions: After meiosis forms the functional megaspore, 3 successive free nuclear mitotic divisions occur to produce the 8-nucleate, 7-celled embryo sac.
ii. Part converted to seed coat: The Integuments (Outer integument forms Testa, Inner integument forms Tegmen).
iii. Passage for pollen tube: The Micropyle.
Question Paper Page No. 1 Question Paper Page No. 2 Question Paper Page No. 3 Question Paper Page No. 4
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Maharashtra Board HSC Biology July 2022 Question Paper Solution

Board Question Paper: July 2022 - Biology

Max. Marks: 70 | Time: 3 Hrs.

SECTION − A

Q.1. Select and write the correct answer for the following multiple choice type of questions:

(i) In lac operon the structural gene z codes for _______ enzyme.

  • (a) \(\beta\)-galactosidase
  • (b) \(\beta\)-galactoside permease
  • (c) transacetylase
  • (d) RNA polymerase
Answer: (a) \(\beta\)-galactosidase

(ii) The special hygroscopic tissue found in the aerial roots of some epiphytic plants is _______.

  • (a) velamen
  • (b) epiblema
  • (c) endodermis
  • (d) xylem
Answer: (a) velamen

(iii) Due to specific mating behaviour, the members of population do not mate in _______ type of isolation.

  • (a) Ecological
  • (b) Seasonal
  • (c) Ethological
  • (d) Mechanical
Answer: (c) Ethological

(iv) The sequence of nitrogenous bases on DNA molecule is ATCGA. Which of the following is the correct complementary sequence of nitrogenous bases on mRNA Molecule?

  • (a) TAGCT
  • (b) TAGCA
  • (c) UAGCU
  • (d) UACGU
Answer: (c) UAGCU

(v) The oral vaccine for prevention of typhoid recommended by WHO is _______.

  • (a) typhoid polysaccharide
  • (b) typhin V
  • (c) typherix
  • (d) Ty21a
Answer: (d) Ty21a

(vi) The large holes in Swiss cheese are developed due to the production of large amounts of _______.

  • (a) \(O_2\)
  • (b) \(CO_2\)
  • (c) \(N_2\)
  • (d) \(H_2\)
Answer: (b) \(CO_2\)

(vii) Miyawaki is a method of plantation adapted by the government for the project mission Harit Kranti from the country.

  • (a) Japan
  • (b) Bhutan
  • (c) China
  • (d) America
Answer: (a) Japan

(viii) In ecological succession, the _______ community does not evolve further.

  • (a) seral
  • (b) pioneer
  • (c) intermediate
  • (d) climax
Answer: (d) climax

(ix) Which of the following sets or organisms are used as cloning organisms in plant biotechnology?

  • (a) E.coli and Rhizobium
  • (b) E.coli and Agrobacterium tumefaciens
  • (c) Azobacterium and Rhizobium
  • (d) E.coli and Azobacterium
Answer: (b) E.coli and Agrobacterium tumefaciens

(x) Aspergillus niger is the microbial source of _______.

  • (a) Vitamin C
  • (b) Vitamin B2
  • (c) Vitamin B12
  • (d) Vitamin B6
Answer: (a) Vitamin C

(Note: While A. niger is primarily the source of Citric Acid, in the context of Maharashtra Board textbook curriculum, it is associated with the production process of Vitamin C.)

HSC Biology

Q.2. Answer the following questions:

(i) Write the name of the small molecule required to initiate / start the process of synthesis of new complementary strand during replication of DNA.

Answer: RNA Primer

(ii) Name the country where industrial melanism was observed in moths due to industrialization.

Answer: Great Britain (England / UK)

(iii) Give the other name for epidermal cells in roots of plants.

Answer: Epiblema cells (or Rhizodermis)

(iv) Name the hormone used for early rooting in propagation by cutting.

Answer: Auxin (specifically Indole Butyric Acid [IBA] or Naphthalene Acetic Acid [NAA])

(v) In human pharynx, there is a set of lymphoid organs called _______.

Answer: Tonsils

(vi) State the other name for Dentist’s nerve.

Answer: Trigeminal nerve (V Cranial Nerve)

(vii) Name the type of Mycorrhiza that grows in between and within the cortical cells of root.

Answer: Endomycorrhiza (or VAM - Vesicular Arbuscular Mycorrhiza)

(viii) Identify the part labelled ‘A’ in the given diagram:

Blastocyst Diagram Placeholder

(Diagram shows a Blastocyst where A points to the outer layer of cells)

Answer: Trophoblast

SECTION − B

Attempt any EIGHT of the following questions:

Q.3. Sketch and label the diagram of ovule most commonly seen in angiosperms.

Answer:

The most common type is the Anatropous Ovule.

diagram of ovule most commonly seen in angiosperms [Diagram of Anatropous Ovule]
Key Labels required:
1. Funiculus
2. Hilum
3. Integuments (Outer and Inner)
4. Micropyle
5. Nucellus
6. Embryo Sac (Female Gametophyte)
7. Chalaza

Q.4. Explain “Law of dominance” with suitable example.

Answer:

Law of Dominance: It states that when two homozygous individuals with one or more sets of contrasting characters are crossed, the alleles (characters) that appear in the F1 generation are called dominant and those that do not appear in F1 are called recessive.

Example: In Pea plants, when a pure tall plant (TT) is crossed with a pure dwarf plant (tt):

  • Parents: Tall (TT) x Dwarf (tt)
  • Gametes: (T) and (t)
  • F1 Generation: Tt (All plants are Tall)

Here, the character 'Tallness' appears in the F1 generation, so it is dominant, while 'Dwarfness' is suppressed, so it is recessive.

Q.5. A woman is unable to conceive due to blockage in her upper segment of oviduct. State the infertility treatment to be given to her and describe it.

Answer:

Treatment: In Vitro Fertilization (IVF) or Test Tube Baby technique.

Description:

  • In this method, the ova from the wife (or donor) and sperms from the husband (or donor) are collected.
  • Fertilization is induced outside the body in a laboratory culture medium (simulating body conditions).
  • The zygote or early embryo (up to 8 blastomeres) is then transferred into the fallopian tube (ZIFT - Zygote Intrafallopian Transfer) or if it has more than 8 blastomeres, it is transferred into the uterus (IUT - Intra Uterine Transfer) for further development.

Q.6. Identify the types of chromosomal aberrations in the following figures A, B, C, D:

Identify the types of chromosomal aberrations in the following figures A, B, C, D [Diagram of hromosomal aberrations]
Answer:
  • A: Deletion (Loss of a segment of chromosome).
  • B: Duplication (A segment of chromosome is repeated).
  • C: Inversion (A segment of chromosome breaks and rejoins in reverse direction).
  • D: Translocation (Exchange of segments between non-homologous chromosomes).

Q.7. The process of transcription takes place on a part of DNA molecule known as transcription unit. Draw a well labelled diagram of the same showing different regions of the unit.

Answer:
Diagram of Transcription Unit [Diagram of Transcription Unit]
Labels required:
1. Promoter (at 5' end of coding strand)
2. Structural Gene
3. Terminator (at 3' end of coding strand)
4. Template Strand (3' to 5' polarity)
5. Coding Strand (5' to 3' polarity)

Q.8. Identify labels A, B, C, D:

Diagram of Transcription Unit

(Refer to Oogenesis diagram in the question paper)

Answer:
  • A: Primary Oocyte (2n)
  • B: Secondary Oocyte (n)
  • C: Ovum / Ootid (n)
  • D: Second Polar Body (n)

Q.9. Match the pairs and rewrite:

Answer:
Column I Column II
(a) Connecting link between ape and man (4) Australopithecus
(b) Ape man (1) Homo erectus
(c) Handy man like (2) Homo habilis
(d) Advanced prehistoric man (3) Neanderthal man

Q.10. Define polyembryony. State its different types.

Answer:

Definition: The phenomenon of development of more than one embryo inside the seed is called polyembryony.

Types:

  1. Simple Polyembryony: Due to fertilization of more than one egg cell.
  2. Cleavage Polyembryony: Due to splitting of the proembryo.
  3. Adventive Polyembryony: Embryos develop from diploid cells of nucellus or integuments (e.g., Citrus, Mango).

Q.11. Which are the major abiotic factors that influence habitat?

Answer:

The major abiotic factors are:

  1. Temperature: Affects enzyme kinetics and basal metabolism.
  2. Water: Essential for life; affects productivity and distribution.
  3. Light: Required for photosynthesis and photoperiodism.
  4. Soil (Edaphic factors): Composition, grain size, and aggregation determine vegetation.

Q.12. Identify A and B in the given diagram and explain T wave.

Diagram of Transcription Unit
Answer:
  • A: P-wave (represents atrial depolarization).
  • B: QRS complex (represents ventricular depolarization).

Explanation of T wave: It represents ventricular repolarization. It marks the return of the ventricles from an excited to a normal state (relaxation phase). The end of the T-wave marks the end of systole.

Q.13. Water acts as a thermal buffer. Justify the statement.

Answer:

Water acts as a thermal buffer because:

  • It has a high specific heat capacity, meaning it can absorb or lose a large amount of heat with only a small change in its own temperature. This helps in maintaining a constant body temperature.
  • It has a high heat of vaporization, allowing organisms to cool down efficiently through evaporation (sweating/transpiration) without losing excessive body fluid.
  • It has high heat of fusion, preventing body fluids from freezing easily.

Q.14. The following diagram indicates which type of interaction? Write a note on the same.

Diagram of Transcription Unit
Answer:

Interaction Type: Mutualism (Specifically, a Lichen).

Note:

  • The diagram shows an intimate association between Algae (phycobiont) and Fungi (mycobiont).
  • This is an example of Mutualism where both species benefit.
  • The algae prepare food through photosynthesis for the fungus.
  • The fungus provides shelter and absorbs water and minerals from the soil for the algae.

SECTION − C

Attempt any EIGHT of the following questions:

Q.15. Suresh is doing his studies on a plant related to absorption of water. He found different forms of water available in the soil.

(i) Name them.
(ii) Which form of water is absorbed by the plants?
(iii) Name the region in the soil from where roots absorb water.

Answer:

(i) Forms of soil water: Gravitational water, Hygroscopic water, Combined water, and Capillary water.

(ii) Absorbed form: Capillary water.

(iii) Region: Rhizosphere (specifically the Zone of Absorption or Root Hair Zone).

Q.16. Name the stress hormone in plants. Describe its physiological effects.

Answer:

Name: Abscisic Acid (ABA).

Physiological Effects:

  • Stomatal Closure: It induces closure of stomata during water stress (drought) to reduce transpiration.
  • Seed Dormancy: It induces dormancy in seeds and buds to withstand unfavorable conditions.
  • Abscission: It promotes the abscission (falling) of leaves, flowers, and fruits.
  • Inhibition of Growth: It generally acts as a growth inhibitor.

Q.17. (a) Sketch and label the diagram of brain to show ventricles in coronal plane.
(b) Name the cavity which is continuation of IV ventricle.

Answer:

(a) Diagram:

Neat labelled diagram of Sketch of Brain Ventricles. - Biology [Sketch of Brain Ventricles]
Labels: Lateral Ventricles, Third Ventricle (Diocoel), Fourth Ventricle (Metacoel), Foramen of Monro, Iter.

(b) Cavity: The central canal of the spinal cord is the continuation of the IV (fourth) ventricle.

Q.18. Complete the following chart and rewrite:

Complete the following chart and rewrite
Answer:
Blood Group Genotype Antigen on Surface of RBC Antibody in serum
A \(I^A I^A\) or \(I^A I^O\) A Anti-B (b)
B \(I^B I^B\) or \(I^B I^O\) B a (Anti-A)
AB \(I^A I^B\) A and B (Nil)
O \(I^O I^O\) (Nil) Anti-A and Anti-B (a and b)

Q.19. Explain the various steps of biogas production.

Answer:

Biogas production involves anaerobic digestion in three stages:

  1. Hydrolysis (Solubilization): Complex organic polymers (cellulose, proteins, fats) are broken down into simple soluble monomers by hydrolytic bacteria (e.g., Clostridium).
  2. Acidogenesis: The monomers are converted into simple organic acids (acetic acid, formic acid) by acidogenic bacteria.
  3. Methanogenesis: Methanogenic bacteria (e.g., Methanococcus, Methanobacillus) convert the organic acids into Methane (\(CH_4\)), Carbon dioxide (\(CO_2\)), and other gases.

Q.20. How ‘melt in mouth’ vaccines are administered? Mention any two benefits of the same.

Answer:

Administration: 'Melt in mouth' vaccines are administered by placing them under the tongue or simply eating them (e.g., edible vaccines in transgenic plants/fruits) where they dissolve and are absorbed into the bloodstream.

Benefits:

  1. They eliminate the need for needles/injections, increasing patient compliance (needle-free).
  2. They can be stored at room temperature, reducing the cost and logistics of a cold chain (refrigeration).

Q.21. Enumerate or enlist the various levels of biodiversity. Explain any one of it.

Answer:

Levels of Biodiversity:

  1. Genetic Diversity
  2. Species Diversity
  3. Ecological (Ecosystem) Diversity

Explanation (Genetic Diversity):

It refers to the variation in genes within a particular species. It allows a population to adapt to changing environments. For example, there are thousands of varieties of rice or mangoes in India, which differ in their genetic makeup.

Q.22. Write down various sequential stages of hydrarch succession in plants after phytoplankton stage.

Answer:

The sequential stages after the Phytoplankton stage are:

  1. Submerged Plant Stage: (e.g., Hydrilla, Vallisneria)
  2. Submerged Free-Floating Plant Stage: (e.g., Pistia, Eichhornia)
  3. Reed-Swamp Stage (Amphibious stage): (e.g., Typha, Sagittaria)
  4. Marsh-Meadow Stage: (e.g., Cyperus, Grasses)
  5. Scrub Stage: (Shrubs like Salix)
  6. Climax Forest: (Trees / Mesophytic vegetation)

Q.23. With the help of a suitable example, write the mechanism of hormone action through membrane receptors.

Answer:

This mechanism is for peptide/protein hormones (e.g., FSH, Insulin) which cannot cross the cell membrane.

Mechanism:

  1. Binding: The hormone (First Messenger) binds to a specific receptor on the cell membrane to form a Hormone-Receptor Complex.
  2. Activation: This complex triggers the release of an enzyme (like Adenylate cyclase).
  3. Second Messenger: The enzyme converts ATP into cyclic AMP (cAMP) or releases \(Ca^{++}\). cAMP acts as the Second Messenger.
  4. Biochemical Response: The second messenger activates intracellular enzyme systems that regulate cellular metabolism, leading to the specific physiological response.

Example: FSH binds to ovarian cell membrane receptors -> generates cAMP -> promotes ovarian follicle growth.

Q.24. Classify the given proteins produced by rDNA technology to treat various diseases in human and rewrite as shown in the table:

Answer:
Disorders / Diseases / Health Conditions Recombinant Protein (s)
Atherosclerosis Platelet derived growth factor
Anaemia Erythropoietin
Parturition Relaxin
Blood clots Tissue plasminogen activator
Diabetes Insulin
Haemophilia A Factor VIII
Haemophilia B Factor IX

Q.25. Write a note on transport of carbon dioxide by bicarbonate ions at tissue level.

Answer:

About 70% of \(CO_2\) is transported in this form.

  • In RBCs, \(CO_2\) reacts with water in the presence of the enzyme Carbonic Anhydrase to form Carbonic acid (\(H_2CO_3\)).
  • \(H_2CO_3\) is unstable and dissociates into Bicarbonate ions (\(HCO_3^-\)) and Hydrogen ions (\(H^+\)).
  • The \(HCO_3^-\) ions diffuse out of the RBCs into the plasma.
  • To maintain ionic balance, Chloride ions (\(Cl^-\)) move from plasma into the RBCs. This is called the Chloride Shift or Hamburger Phenomenon.
  • This process allows blood to carry \(CO_2\) efficiently to the lungs.

Q.26. Anita observed apical dominance in her plant. Name and describe the plant hormone that will reverse the effect.

Answer:

Name: Cytokinin.

Description:

  • Cytokinins promote cell division (cytokinesis).
  • They counteract apical dominance induced by Auxins.
  • By applying Cytokinins, the growth of lateral buds is stimulated even in the presence of the apical bud, making the plant bushy.

SECTION − D

Attempt any THREE of the following questions:

Q.27. (a) Kabban Park in Bengaluru is having dull flowers with strong fragrance, abundant nectar and edible pollen grains. Identify the type of pollination, the flowers are adapted for.
(b) The process of fruit formation without fertilization is termed as _______.
(c) Differentiate between albuminous and exalbuminous seeds.

Answer:

(a) Type of Pollination: Chiropterophily (Pollination by Bats). The characteristics (dull color, strong fragrance, abundant nectar) are adaptations for nocturnal pollinators like bats.

(b) Parthenocarpy.

(c) Difference:

Albuminous (Endospermic) Seeds Exalbuminous (Non-endospermic) Seeds
Endosperm persists in the mature seed. Endosperm is completely consumed during embryo development.
Food is stored in the endosperm. Food is stored in the cotyledons.
Example: Maize, Castor, Wheat. Example: Pea, Bean, Gram.

Q.28. Give reasons :
(a) Though fertilization takes place in the ampulla of fallopian tube, implantation of embryo takes place after reaching the uterus only.
(b) Corpus luteum persists in the ovary after fertilization.
(c) Explain the role of oxytocin hormone and describe the dilation stage of parturition.

Answer:

(a) Reason: The fertilized egg (zygote) undergoes cleavage as it moves towards the uterus. It takes about 4-7 days to form a blastocyst. Implantation requires the blastocyst stage and a prepared uterine endometrium, which prevents ectopic pregnancy and ensures proper nourishment.

(b) Reason: After fertilization, the trophoblast cells of the embryo secrete hCG (Human Chorionic Gonadotropin). This hormone signals the Corpus Luteum to persist and continue secreting Progesterone, which is essential to maintain the endometrium and the pregnancy until the placenta takes over.

(c) Oxytocin and Dilation Stage:

  • Role of Oxytocin: It acts on the uterine muscles and causes stronger uterine contractions (Labor pains). This creates a positive feedback loop leading to expulsion of the baby.
  • Dilation Stage: This is the first stage of parturition. Uterine contractions begin from the top. The cervix dilates (opens) fully (up to 10cm). The amniotic sac ruptures, releasing amniotic fluid. This stage lasts for about 12 hours.

Q.29. Give the graphic representation of back cross and test cross. Differentiate between them.

Answer:

Graphic Representation:

Let T = Tall (Dominant), t = Dwarf (Recessive). F1 Hybrid = Tt.

  • Back Cross: F1 Hybrid (Tt) x Any Parent (TT or tt).
  • Test Cross: F1 Hybrid (Tt) x Recessive Parent (tt).

Differentiation:

Back Cross Test Cross
Cross between F1 hybrid and any one of the parents (Dominant or Recessive). Cross between F1 hybrid and the homozygous recessive parent only.
Used to improve breeds or traits. Used to determine the unknown genotype of the F1 hybrid.
All test crosses are back crosses. All back crosses are not test crosses.

Q.30. (a) Name the nerve fibres internally connecting the cerebral hemispheres.
(b) Name the sulci which divide each cerebral hemisphere into 4 lobes.
(c) Describe the various functional areas found in the different lobes of cerebral hemispheres.

Answer:

(a) Connection: Corpus callosum.

(b) Sulci:

  • Central Sulcus (divides Frontal and Parietal).
  • Lateral Sulcus (divides Frontal/Parietal and Temporal).
  • Parieto-occipital Sulcus (divides Parietal and Occipital).

(c) Functional Areas:

  • Frontal Lobe: Motor area (voluntary movements), Broca’s area (speech production), Association area (intellect, memory).
  • Parietal Lobe: Somatosensory area (sensation of pain, touch, temperature, pressure).
  • Temporal Lobe: Auditory area (hearing), Wernicke’s area (understanding speech/language), Olfactory area (smell).
  • Occipital Lobe: Visual area (vision and visual interpretation).

Q.31. (a) Describe the structure of lymphocytes and mention its types.
(b) Name the disorder caused due to abnormal and uncontrolled increase in number of WBCs.
(c) State the functions of neutrophils.

Answer:

(a) Structure & Types of Lymphocytes:

  • Structure: They are agranulocytes with a large, spherical nucleus and very little peripheral cytoplasm. They constitute 25-30% of WBCs.
  • Types:
    1. B-Lymphocytes: Mature in bone marrow; produce antibodies (humoral immunity).
    2. T-Lymphocytes: Mature in thymus; responsible for cell-mediated immunity (Helper T, Cytotoxic T, Suppressor T, Memory T cells).

(b) Disorder: Leukemia (Blood Cancer).

(c) Functions of Neutrophils:

  • They are the first line of defense against pathogens.
  • They perform phagocytosis (engulfing and destroying bacteria/pathogens).
  • They release pus after dying at the site of infection.
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Chapter wise weightage for HSC Biology

Chapter wise weightage for HSC Biology


Biology is important for a Science student of Class 12 Maharashtra Board, because it helps us to understand the study of life and tells us about the natural world. The syllabus of Class 12 Biology includes topics like microbes in human, welfare, reproduction, etc.


The chapter wise weightage for HSC Biology Maharashtra Board helps the students to know, on which topic to concentrate more. This helps them to score good marks in their HSC exam. The understanding of Maharashtra State Board 12th Biology syllabus is must, so that the students can make a preparation plan to clear the Class 12 Board exam with good grades.


Biology is an interesting subject, which is all about life, its composition, development and about nature, environment, experiments, inventions and lot more.


Chapter wise Weightage for HSC Biology

Types of Question

Marks

Marks with option

Percentage

Objective

14

14

20

Short Answers

42

56

60

Brief Answers

14

28

20

Total

70

98

100


Distribution of Marks According to Units

Sl No

Unit

Marks without option

Marks with option

1

Genetic Basis of Inheritance

8

12

2

Gene: It’s Nature, Expression and Regulation

8

12

3

Biotechnology: Process and Application

7

9

4

Enhancement in Food Production

7

9

5

Microbes in Human Welfare

3

5

6

Photosynthesis

7

9

7

Respiration

7

9

8

Reproduction in Plants

7

9

9

Organisms and Environment – I

7

5

10

Origin and Evolution of Life

7

9

11

Chromosomal Basis of Inheritance

7

9

12

Genetic Engineering and Genomics

3

5

13

Human Health and Diseases

5

7

14

Animal Husbandry

5

7

15

Circulation

10

14

16

Excretion and Osmoregulation

10

14

17

Control and Co-ordination

10

14

18

Human Reproduction

7

9

19

Organisms and


Environment – II

3

5


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