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

Maharashtra Board Class 12 Biology Question Paper Solutions July 2024

BOARD QUESTION PAPER: JULY 2024 - BIOLOGY SOLUTIONS

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 monocot embryo the protective sheath of plumule is called __________.
Answer: (D) coleoptile
ii. The synonymous term for centromere is ________.
Answer: (A) primary constriction
iii. Protein digesting enzyme is ________.
Answer: (B) protease
iv. Spermatids get transformed into a functional spermatozoa by the process of ________.
Answer: (A) spermiogenesis
v. Industrial melanism is one of the best example of ________.
Answer: (B) natural selection
vi. Value of root pressure is +1 to +2 bars which is enough to pump water to a height of ________.
Answer: (B) 10-20 meters
vii. ________ cellular fragments are formed from megakaryocytes.
Answer: (C) Thrombocytes
viii. Degeneration of dopamine producing neurons in the CNS causes ________.
Answer: (D) Parkinson's disease
ix. Choose the correct name of phases A, B and C in the given figure:
Answer: (D) Lag, Log, Stationary
x. Rivet Popper Hypothesis explains
Answer: (A) loss of biodiversity

HSC Biology

Q.2. Answer the following questions:

i. Write the ratio of methane, ammonia and hydrogen respectively in Urey and Miller's experiment.
The ratio of methane ($CH_4$), ammonia ($NH_3$), and hydrogen ($H_2$) in Urey and Miller's experiment is 2:1:2.
ii. What are the cells of Rauber?
The cells of the trophoblast that are in contact with the embryonal knob (inner cell mass) are called cells of Rauber.
iii. Which gene is introduced in tobacco against pest like Zabrotes subfasciatus?
The Arcelin gene (from Phaseolus vulgaris) is introduced in tobacco against Zabrotes subfasciatus.
iv. How many haploid nuclei are present in mature female gametophyte of Angiosperms?
There are 8 haploid nuclei present in a mature female gametophyte of Angiosperms.
v. Name the connection between pulmonary trunk and aortic arch representing remnant of embryonic ductus arteriosus.
Ligamentum arteriosum.
vi. Which endocrine gland plays an important role in the development of immune system?
Thymus gland.
vii. Mention the type of association between sea anemone and clown fish.
Commensalism.
viii. Name the pioneer species in the aquatic habitat during primary succession.
Phytoplanktons.

SECTION – B

Attempt any EIGHT of the following questions:

Q.3. i. Why DNA replication is called semi-conservative replication?
ii. Name the scientist who experimentally proved the same.
i. DNA replication is called semi-conservative because in the newly formed DNA molecule, one strand is old (parental) and conserved, while the other strand is newly synthesized.
ii. Matthew Meselson and Franklin Stahl experimentally proved this.
Q.4. Distinguish between Asexual and Sexual reproduction with reference to:
i. Cell division
ii. Genetic makeup
Feature Asexual Reproduction Sexual Reproduction
i. Cell division It involves only mitosis (or amitosis). It involves both meiosis (during gamete formation) and mitosis.
ii. Genetic makeup Offspring are genetically identical to the parent (Clones). Offspring show genetic variation due to recombination.
Q.5. Arrange the following stages of human evolution in the order of their increasing cranial capacity:
i. Homo sapiens
ii. Neanderthal man
iii. Australopithecus
iv. Homo erectus
Correct Order: iii \(\to\) iv \(\to\) ii \(\to\) i

1. Australopithecus (approx 450-600 cc)
2. Homo erectus (approx 900 cc)
3. Neanderthal man (approx 1400 cc)
4. Homo sapiens (approx 1450 cc)
Q.6. Identify chromosomal disorder caused due to non-disjunction of 21st chromosome and enlist its characteristics.
Disorder: Down's Syndrome (Trisomy 21).
Characteristics:
  • Mild to moderate mental retardation.
  • Flat face with a protruding tongue.
  • Slanting eyes with epicanthal folds.
  • Short stature and stubby fingers.
Q.7. What is radial and tangential translocation of food in plants?
  • Radial Translocation: Transport of food from the phloem to the pith or cortex (in a lateral direction) via medullary rays is called radial translocation.
  • Tangential Translocation: Transport of food in a direction perpendicular to the radius (around the circumference) is called tangential translocation.
Q.8. Explain any two causes of genetic variation.
  1. Gene Mutation: Sudden permanent change in the genetic material (DNA) leads to new traits and variation.
  2. Genetic Recombination (Crossing Over): During meiosis (Prophase I), the exchange of genetic material between non-sister chromatids of homologous chromosomes creates new combinations of genes.
Q.9. Identify A, B, C and D from the following table regarding respiratory system:
OrganismHabitatRespiratory organ
ATerrestrialTracheal tubes and spiracles
ScorpionsTerrestrialB
SpongesCPlasma membrane
TurtlesUnderwaterD

Solution:
A: Insects (e.g., Cockroach)
B: Book lungs
C: Aquatic
D: Cloaca (or Lungs/Plastron depending on specific context of aquatic respiration modes)
Q.10. Give the function of Nebenkern and Zona pellucida.
  • Nebenkern: It is the spirally arranged mitochondria in the middle piece of the sperm. It provides energy (ATP) for the movement of the sperm.
  • Zona pellucida: It is a glycoprotein layer surrounding the plasma membrane of the mammalian ovum. It ensures species-specific fertilization and prevents polyspermy (along with cortical reaction).
Q.11. Give location of corpus callosum and arbor vitae of human brain.
  • Corpus callosum: Located deep within the longitudinal fissure, connecting the two cerebral hemispheres of the forebrain.
  • Arbor vitae: Located in the cerebellum (hindbrain); it is the tree-like branching pattern of white matter within the cerebellar hemispheres.
Q.12. Match cells of immune system in column-I and their functions in column-II and rewrite it.
Column-I Column-II (Correct Match)
i. Cytotoxic T cells (c) Secretion of perforins
ii. Plasma cells (d) Antibody production
iii. Antigen presenting cells (a) Activation of helper T cells
iv. Red blood cells (b) Blood group antigens
Q.13. Give any two examples of commercially exploited products of transgenic plants.
  1. Bt Cotton: Produces insecticidal protein to resist bollworms.
  2. Golden Rice: Genetically modified to produce Pro-vitamin A (Beta-carotene).
  3. (Alternative) Flavr Savr Tomato: Delayed ripening for longer shelf life.
Q.14. Write causative agent, two symptoms and mode of transmission of typhoid.
  • Causative agent: Salmonella typhi.
  • Symptoms: High fever, stomach pain, loss of appetite, constipation.
  • Mode of transmission: Fecal-oral route (ingestion of contaminated food and water).

SECTION – C

Attempt any EIGHT of the following questions:

Q.15. Suggest the specific term for the following:
i. Both male and female reproductive organs present in same organism.
ii. Y-linked gene.
iii. Unfertilised egg develops into haploid male bee.
i. Hermaphrodite / Bisexual / Monoecious.
ii. Holandric gene.
iii. Arrhenotoky (Parthenogenesis).
Q.16. Explain the role of diazotrophs in nitrification.
Wait, the question asks about diazotrophs in nitrification? Diazotrophs are typically nitrogen fixers ($N_2 \to NH_3$). Nitrification is carried out by nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter).

Clarified Answer:
Diazotrophs (like Azotobacter, Rhizobium, Nostoc) fix atmospheric nitrogen ($N_2$) into ammonia ($NH_3$). This ammonia then becomes the substrate for nitrification.
Nitrification process:
  1. Ammonia is oxidized to Nitrite ($NO_2^-$) by Nitrosomonas.
  2. Nitrite is further oxidized to Nitrate ($NO_3^-$) by Nitrobacter.
Thus, diazotrophs provide the initial fixed nitrogen required for the nitrification process to occur in the soil.
Q.17. Explain the following events of cardiac cycle with respect to type of valves and duration:
i. atrial systole
ii. ventricular systole
iii. joint diastole
Event Duration Valves Status
i. Atrial Systole 0.1 sec Atrioventricular (AV) valves (Tricuspid & Bicuspid) are Open. Semilunar valves are closed. Blood is pumped into ventricles.
ii. Ventricular Systole 0.3 sec AV valves Close (producing 'Lubb' sound). Semilunar valves Open. Blood is pumped into Pulmonary trunk and Aorta.
iii. Joint Diastole 0.4 sec Semilunar valves Close (producing 'Dubb' sound). AV valves Open. All chambers are in relaxed state; passive filling occurs.
Q.18. What is reflex action? Explain with one example each of the types of reflex actions based on previous experiences.
Reflex Action: It is a sudden, spontaneous, automatic, and involuntary response to a stimulus, mediated by the spinal cord or brain stem.

Types based on experience:
  1. Unconditioned Reflex (Inborn): Does not require previous experience or learning.
    Example: Salivation on tasting food, withdrawal of hand from a hot object.
  2. Conditioned Reflex (Acquired): Requires previous experience, learning, or training.
    Example: Salivation in a dog just by hearing a bell (Pavlov's experiment), or playing a musical instrument, cycling.
Q.19. Select and fill in the boxes (a) to (f) from given list of options.
List of options: Sickle cell anaemia, Widow’s peak, Flower colour of Mirabilis, Human blood groups, Coat colour of cattle, Klinefelter’s syndrome.

Genetic trait Example
i. Incomplete dominance(a) Flower colour of Mirabilis
ii. Pleiotropy(b) Sickle cell anaemia
iii. Codominance(c) Coat colour of cattle (Roan) (or Human blood groups AB)
iv. Multiple allelism(d) Human blood groups (ABO)
v. Sex chromosomal disorder(e) Klinefelter's syndrome
vi. Autosomal disorder (or trait)(f) Widow's peak
Q.20. Give the role of following mycoherbicides
i. Phytophthora
ii. Alternaria
iii. Fusarium
  • i. Phytophthora palmivora: Controls milkweed vines in citrus orchards. (Commercial name: Devine).
  • ii. Alternaria crassa: Controls water hyacinth.
  • iii. Fusarium sp.: Used to control various weeds.
Q.21. Explain the following terms with respect to survival of an organism in a changed environment.
i. Regulate
ii. Conform
iii. Migrate
  • i. Regulate: Organisms maintain a constant internal environment (homeostasis) despite changes in the external environment (e.g., mammals maintaining body temperature).
  • ii. Conform: Organisms cannot maintain a constant internal environment; their body temperature or osmotic concentration changes with the ambient environment (e.g., most fishes, reptiles).
  • iii. Migrate: Organisms move temporarily from a stressful habitat to a more hospitable area and return when the stressful period is over (e.g., migratory birds).
Q.22. Describe any three causes for loss of biodiversity.
  1. Habitat Loss and Fragmentation: Destruction of natural habitats due to urbanization and deforestation is the primary cause. Breaking large habitats into smaller fragments affects migratory animals.
  2. Over-exploitation: Excessive hunting or harvesting of species by humans for food, medicine, or profit leads to extinction (e.g., Stellar's sea cow).
  3. Invasion of Alien Species: Introduction of non-native species can cause the decline or extinction of indigenous species (e.g., Water hyacinth, Nile Perch).
Q.23. Give physiological effects and applications of cytokinin.
Physiological Effects & Applications:
  • Cell Division: Promotes cytokinesis (cell division) in presence of auxin.
  • Delay of Senescence: Delays the aging of leaves (Richmond-Lang effect) by retaining chlorophyll. Used to increase shelf life of vegetables.
  • Morphogenesis: Promotes shoot formation (caulogenesis) in tissue culture.
  • Breaking Dormancy: Breaks seed and bud dormancy.
Q.24. What is mycorrhiza? Name its types and state any two benefits of mycorrhiza.
Definition: Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
Types:
  1. Ectomycorrhiza (Fungal hyphae form a mantle outside the root).
  2. Endomycorrhiza (Fungal hyphae penetrate root cells, e.g., VAM).
Benefits:
  • Enhances absorption of water and minerals (especially Phosphorus).
  • Provides resistance to root-borne pathogens.
Q.25. i. Explain the following:
a. Leaching
b. Humification and mineralization
ii. What is humus?
i. a. Leaching: The process where water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
i. b. Humification and Mineralization:
  • Humification: Process of formation of a dark-coloured amorphous substance called humus.
  • Mineralization: The process where humus is further degraded by some microbes to release inorganic nutrients.
ii. Humus: It is a dark-coloured, amorphous organic substance that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. It serves as a reservoir of nutrients.
Q.26. i. What is hematocrit?
ii. Mention the term with respect to –
a. Temporary increase in number of WBCs
b. Decrease in number of RBCs
i. Hematocrit: It is the ratio of the volume of red blood cells to the total volume of blood (also called Packed Cell Volume - PCV).
ii. Terms:
a. Temporary increase in number of WBCs: Leukocytosis.
b. Decrease in number of RBCs: Erythrocytopenia (or Anemia).

SECTION – D

Attempt any THREE of the following questions:

Q.27. Describe mechanism of opening and closing of stomata with reference to:
i. Starch-sugar interconversion theory
ii. Proton transport theory
i. Starch-sugar interconversion theory (Steward/Lloyd):
  • Daytime (Opening): Photosynthesis consumes \(CO_2\), pH rises. Starch phosphorylase converts insoluble Starch into soluble Glucose-1-phosphate. Osmotic pressure of guard cells increases, water enters (endosmosis), guard cells become turgid, and stomata open.
  • Nighttime (Closing): pH drops. Glucose-1-phosphate is reconverted to insoluble Starch. Osmotic pressure decreases, water leaves (exosmosis), guard cells become flaccid, and stomata close.
ii. Proton transport theory (Levitt):
  • Opening: Usually during the day, protons ($H^+$) are actively pumped out of guard cells into subsidiary cells. In exchange, Potassium ions ($K^+$) enter guard cells (Active transport). Malate ions balance the charge. Increased $K^+$ and Malate concentration increases osmotic potential, causing endosmosis and stomatal opening.
  • Closing: Abscisic Acid (ABA) reverses this process. $K^+$ ions flow out, guard cells lose water and become flaccid.
Q.28. i. Define hormone.
ii. Enlist any two properties of hormones.
iii. Give diagrammatic representation of mode of hormone action through membrane bound receptors.
i. Definition: Hormones are chemical messengers (intercellular messengers) produced by endocrine glands in trace amounts, released directly into the blood, and act on specific target organs/cells.
ii. Properties:
  • They are required in very low concentrations.
  • They are highly specific to their target receptors.
iii. Diagrammatic Representation:
Diagram of Mechanism of Hormone Action (Membrane Bound Receptor)
(Diagram showing: Hormone (First messenger) \(\to\) Receptor on Cell Membrane \(\to\) Generation of Second Messenger (e.g., cAMP) \(\to\) Biochemical response \(\to\) Physiological response)
Q.29. With respect to diagram, answer the following:
Anatropous Ovule Diagram from Question Paper
(Refer to the diagram in the question paper image above)

i. Which type of ovule is given in the figure?
ii. Name the first cell of embryo sac.
iii. Identify and write the function of ‘A’ and ‘B’.
i. Type of ovule: Anatropous ovule (Inverted ovule).
ii. First cell of embryo sac: Functional Megaspore.
iii. Identification and Function:
  • A (Funiculus): It is the stalk that attaches the ovule to the placenta. It provides nutrition to the developing ovule.
  • B (Secondary Nucleus / Definitive Nucleus): It is diploid (2n). It fuses with the second male gamete during double fertilization to form the Primary Endosperm Nucleus (PEN), which develops into the nutritive tissue called endosperm.
Q.30. How transgenic pigs and cattle are commercially beneficial?
Transgenic Pigs:
  • Organ Transplantation (Xenotransplantation): Pigs are modified to produce organs that are less likely to be rejected by the human immune system.
  • Meat Production: Modified for leaner meat and faster growth.
Transgenic Cattle:
  • Molecular Pharming: Cows act as bioreactors to produce human therapeutic proteins (e.g., human lactoferrin) in their milk.
  • Increased Production: Modified for increased milk yield (casein variants).
  • Disease Resistance: Engineered to be resistant to specific bovine diseases (e.g., mastitis).
Q.31. With the help of a suitable diagram describe histology of testis.
Histology of Testis (Description):
  • Externally covered by three layers: Tunica vaginalis (outer), Tunica albuginea (middle fibrous), and Tunica vasculosa (inner vascular).
  • The testis contains numerous Seminiferous Tubules.
  • Seminiferous Tubule Structure:
    • Lined by Germinal Epithelium consisting of cuboidal Spermatogonia (male germ cells) and columnar Sertoli cells (Nurse cells).
    • Spermatogonia undergo spermatogenesis to form: Primary Spermatocytes \(\to\) Secondary Spermatocytes \(\to\) Spermatids \(\to\) Spermatozoa (Sperms).
    • Sertoli cells provide nutrition to developing sperms and form the blood-testis barrier.
  • Interstitial Space: The space between tubules contains connective tissue and Leydig cells (Interstitial cells), which secrete testosterone (androgen).
T.S. of Testis Diagram
(Diagram required showing: Seminiferous tubules, Germinal epithelium, Spermatogonia, Sperm bundles, Sertoli cells, and Leydig cells in interstitial space)
Question Paper Page No. 1 Question Paper Page No. 2 Question Paper Page No. 3 Question Paper Page No. 4 Maharashtra Board Question Paper
Labels: , , , , , ,

Maharashtra Board Class 12 Biology Question Paper Solution 2024

Biology (56) - 2024 Solution

Maximum Marks: 70 | Time: 3 Hrs.

SECTION – A

Q. 1. Select the correct alternatives and write the answers :

(i) Identify the growth hormone in plants which causes inhibitory effect.

  • (a) Cytokinins
  • (b) Abscissic acid
  • (c) Gibberellin
  • (d) Ethylene
Answer: (b) Abscissic acid

(ii) Which one of the following is not a part of lac operon?

  • (a) Promoter
  • (b) Regulator
  • (c) Inducer
  • (d) Operator
Answer: (c) Inducer

(iii) In absence of fertilization, corpus luteum degenerates into _____.

  • (a) tunica albugenia
  • (b) membrana granulosa
  • (c) zona pellucida
  • (d) corpus albicans
Answer: (d) corpus albicans

(iv) Which of the following divides nasal cavity?

  • (a) Hyaline cartilage
  • (b) Mesethmoid cartilage
  • (c) Ligamentum arteriosum
  • (d) Laryngopharynx
Answer: (b) Mesethmoid cartilage

(v) Which of the following is caused by unsterilized needle?

  • (a) Elephantiasis
  • (b) AIDS
  • (c) Malaria
  • (d) Dengue
Answer: (b) AIDS

(vi) Recognition sequence of restriction enzymes are generally _____ nucleotides long.

  • (a) 2 to 4
  • (b) 4 to 8
  • (c) 8 to 10
  • (d) 14 to 18
Answer: (b) 4 to 8

(vii) Which of the following types require pollinator but result is genetically similar to autogamy?

  • (a) Geitonogamy
  • (b) Xenogamy
  • (c) Apogamy
  • (d) Cleistogamy
Answer: (a) Geitonogamy

(viii) Which one of the following does not evolve further?

  • (a) Climax community
  • (b) Primary Succession
  • (c) Pioneer Species
  • (d) Seral Community
Answer: (a) Climax community

(ix) Identify the appropriate term for the number of births under ideal conditions :

  • (a) Absolute mortality
  • (b) Realized natality
  • (c) Realized mortality
  • (d) Absolute natality
Answer: (d) Absolute natality

(x) Observe the graph and select correct option :

Species Richness vs Area
  • (a) Line ‘A’ represents \( S-CA^2 \)
  • (b) Line ‘B’ represents \( \log C = \log A + Z \log S \)
  • (c) Line A represents \( S = CA^Z \)
  • (d) Line B represents \( \log S = \log Z + C \log A \)
Answer: (c) Line A represents \( S = CA^Z \)

HSC Biology

Q. 2. Answer the following questions :

(i) What are vestigeal organs?

Answer: Vestigial organs are rudimentary, degenerated, or underdeveloped organs found in an organism that are non-functional but were functional in their ancestors. (e.g., Vermiform appendix in humans).

(ii) Expand the term ZIFT.

Answer: Zygote Intrafallopian Transfer.

(iii) Give the name of endocrine gland which is prominent at birth but gets gradually atrophied in adult stage.

Answer: Thymus gland.

(iv) What is the full form of IAA?

Answer: Indole-3-Acetic Acid.

(v) Give the name of microbial source of antibiotic chloromycetin.

Answer: Streptomyces venezuelae.

(vi) Which cells of islets of Langerhans produce a hormone insulin?

Answer: Beta cells (\( \beta \)-cells).

(vii) How many meiotic divisions are required for the formation of 300 seeds in angiosperm?

Answer: 375 meiotic divisions.
Explanation: For 300 seeds, we need 300 pollen grains and 300 embryo sacs.
- For 300 pollen: \( 300/4 = 75 \) meiotic divisions.
- For 300 embryo sacs: \( 300/1 = 300 \) meiotic divisions.
- Total = 75 + 300 = 375.

(viii) Explain the term Emigration.

Answer: Emigration is the number of individuals of the population who leave the habitat and go elsewhere during the time period under consideration.

SECTION – B

Attempt any EIGHT of the following questions :

Q. 3. What are the reasons for the success of Mendel?
Answer: The reasons for Mendel's success include:
  1. He carefully selected the garden pea plant (Pisum sativum) which was self-fertilizing and easy to grow.
  2. He studied the inheritance of one character at a time (monohybrid) before proceeding to complex crosses.
  3. He kept accurate statistical records of his breeding experiments.
  4. He was fortunate that the characters he chose were located on different chromosomes or showed no linkage.
Q. 4. Arrange the following steps of DNA fingerprinting in correct sequence :
  • (a) Gel electrophoresis
  • (b) Isolation of DNA
  • (c) Southern blotting
  • (d) Restriction digestion
Answer: The correct sequence is: (b) → (d) → (a) → (c).
1. Isolation of DNA
2. Restriction digestion
3. Gel electrophoresis
4. Southern blotting
Q. 5. Distinguish between human sperm and ovum.
Answer:
Human Sperm Human Ovum
It is motile and active. It is non-motile and passive.
It is very small in size. It is larger in size due to cytoplasm.
Mitochondria are arranged spirally in the middle piece. Mitochondria are scattered in the cytoplasm.
Contains X or Y chromosome. Contains only X chromosome.
Q. 6. Enlist the uses of gene therapy.
Answer: Uses of gene therapy include:
  • Replacement of missing or defective genes: E.g., Treatment of SCID (Severe Combined Immunodeficiency) due to ADA deficiency.
  • Destruction of cancer cells: Introducing genes that cause cancer cells to die.
  • Delivery of genetic material: Delivering DNA sequences that code for therapeutic proteins.
  • Treatment of genetic disorders like Cystic fibrosis, Hemophilia, etc.
Q. 7. Define the following terms :
(a) Gene flow
(b) Chromosomal aberrations
Answer:

(a) Gene flow: It is the transfer of genetic material (alleles) from one population to another due to the migration of individuals or gametes.

(b) Chromosomal aberrations: These are the structural changes in the chromosome caused by deletion, duplication, inversion, or translocation of a part of the chromosome, leading to changes in the arrangement of genes.

Q. 8. What are the significances of double fertilization?
Answer:
  • It results in the formation of a diploid zygote, which develops into an embryo.
  • It results in the formation of a triploid Primary Endosperm Nucleus (PEN), which develops into nutritive endosperm tissue for the developing embryo.
  • It restores the diploid condition of the plant life cycle.
  • It ensures that the nutritive tissue (endosperm) is formed only when fertilization occurs, preventing wastage of energy.
Q. 9. Identify and define ‘A’ and ‘B’ in relation to uptake of water by the root :
Species Richness vs Area
Answer:

A - Apoplast pathway: It is the movement of water through the cell walls and intercellular spaces without crossing any membrane or entering the cytoplasm.

B - Symplast pathway: It is the movement of water from cell to cell through the cytoplasm and plasmodesmata.

Q. 10. Describe mutualism.
Answer: Mutualism is a type of biological interaction (symbiosis) between two different species where both organisms benefit from the association. Neither species can survive easily without the other under natural conditions.
Examples: Lichens (association between algae and fungi), Mycorrhiza (association between fungi and roots of higher plants).
Q. 11. Explain factors affecting water absorption.
Answer: Factors affecting water absorption include:
  • Available Soil Water: Water absorption is maximum at field capacity (capillary water).
  • Concentration of Soil Solution: High concentration of salts in soil water decreases absorption (physiological dryness).
  • Soil Aeration: Poorly aerated soils retard absorption as roots need oxygen for respiration.
  • Soil Temperature: Optimum temperature (20°C to 30°C) favors maximum absorption.
  • Transpiration: High rate of transpiration increases the rate of water absorption.
Q. 12. What is differentiation and redifferentiation?
Answer:

Differentiation: It is the process by which cells derived from root apical and shoot-apical meristems and cambium differentiate and mature to perform specific functions.

Redifferentiation: It is the process by which de-differentiated cells (which had regained the capacity to divide) lose their division capacity again and mature to perform specific functions (e.g., formation of secondary cortex, secondary xylem).

Q. 13. Select and rewrite appropriate disorder of respiratory system with the given symptoms :
[ sinusitis, emphysema, silicosis and asbestosis, laryngitis ]

(a) Breakdown of alveoli, shortness of breath.

Answer: Emphysema

(b) Inflammation of the sinuses, mucous discharge.

Answer: Sinusitis

(c) Inflammation of larynx, vocal cord, sore throat, hoarseness of voice, mucous build up and cough.

Answer: Laryngitis

(d) Inflammation of fibrosis, lung damage.

Answer: Silicosis and asbestosis
Q. 14. Explain the steps involved in preliminary treatment of sewage.
Answer: Preliminary treatment involves physical removal of large and small particles from sewage. The steps are:
  1. Screening: Sewage is passed through screens or wire meshes to remove large floating debris like suspended solids, plastics, rags, etc.
  2. Grit Chamber: The sewage is then passed into a grit chamber where the speed of flow is reduced. This allows heavy solid particles like sand, silt, grit, and pebbles to settle down at the bottom.

SECTION – C

Attempt any EIGHT of the following questions :

Q. 15. Give the different steps involved in formation of m-RNA from hn-RNA.
Answer: The process of processing hn-RNA (heterogeneous nuclear RNA) into functional m-RNA in eukaryotes involves:
  1. Splicing: The introns (non-coding sequences) are removed, and exons (coding sequences) are joined together in a defined order.
  2. Capping: An unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of the hn-RNA.
  3. Tailing (Polyadenylation): Adenylate residues (200-300) are added at the 3'-end in a template-independent manner.
The fully processed hn-RNA is now called m-RNA and is transported out of the nucleus.
Q. 16. What is reproductive isolation? Describe any two types each of pre-mating and post-mating isolating mechanism.
Answer:

Reproductive Isolation: It is the mechanism that prevents interbreeding between populations of two different species, maintaining their distinct genetic identities.

Pre-mating Isolating Mechanisms (prevent fertilization):

  • Temporal Isolation: Species breed at different times of the day, season, or year.
  • Ecological (Habitat) Isolation: Species occupy different habitats within the same area and rarely encounter each other.

Post-mating Isolating Mechanisms (prevent hybrid survival/reproduction):

  • Hybrid Sterility: Hybrids are formed but are sterile (e.g., Mule).
  • Zygote Mortality: Fertilization occurs, but the zygote dies before developing.
Q. 17. Explain unique features of acquired immunity.
Answer: The unique features of acquired (adaptive) immunity are:
  1. Specificity: It is specific to a particular pathogen or antigen. It can distinguish between different types of pathogens.
  2. Diversity: It can recognize a vast variety of diverse pathogens.
  3. Discrimination between Self and Non-self: It can differentiate between body's own cells (self) and foreign molecules (non-self).
  4. Memory: When the immune system encounters a pathogen for the first time, it generates a response and retains a 'memory'. If the same pathogen attacks again, the response is faster and stronger (secondary response).
Q. 18. Name and describe hormones secreted by ovaries.
Answer: The ovaries secrete the following hormones:
  • Estrogen: Secreted by growing ovarian follicles. It stimulates the development of female secondary sexual characteristics (high pitch voice, breast development) and regulates the menstrual cycle (growth of endometrium).
  • Progesterone: Secreted by the Corpus Luteum. It is essential for maintaining pregnancy, thickening the endometrium for implantation, and mammary gland development.
  • Relaxin: Secreted by the corpus luteum at the end of gestation. It relaxes the cervix and pelvic ligaments to facilitate childbirth.
  • Inhibin: Inhibits the secretion of FSH (Follicle Stimulating Hormone).
Q. 19. Explain different steps involved in PCR technique.
Answer: PCR (Polymerase Chain Reaction) involves three main steps repeated in cycles:
  1. Denaturation (94-98°C): The double-stranded DNA is heated to separate the two strands by breaking hydrogen bonds.
  2. Annealing (40-60°C): Two sets of primers (small DNA sequences) bind (anneal) to their complementary sequences on the single-stranded DNA templates.
  3. Extension (72°C): The enzyme Taq polymerase extends the primers using the nucleotides provided in the reaction, synthesizing new DNA strands complementary to the templates.
Q. 20. Identify A, B, and C from the above diagrams and give their functions.
Diagram of Blood Cells A (Neutrophil), B (Eosinophil), C (Monocyte)
Answer:
  • A: Neutrophil (Identified by multi-lobed nucleus).
    Function: Phagocytosis (engulfing and destroying pathogens).
  • B: Eosinophil (Identified by bi-lobed nucleus and granules).
    Function: Plays a role in allergic reactions and immunity against parasitic infections; releases histaminase.
  • C: Monocyte (Identified by large kidney-shaped nucleus).
    Function: Phagocytosis; they differentiate into macrophages in tissues to engulf bacteria and cellular debris.
Q. 21. What are the limitations of root pressure theory?
Answer: Limitations of root pressure theory:
  • Root pressure is not found in all plants (e.g., absent in gymnosperms like conifers).
  • The magnitude of root pressure is low (usually 1-2 bars), which is insufficient to push water to the tops of tall trees.
  • Root pressure is often not observed during the day when transpiration is high.
  • It acts slowly and cannot account for the rapid rate of water ascent in most plants.
Q. 22. Explain green house effect with reference to gases responsible for it and their sources.
Answer:

Greenhouse Effect: It is the natural phenomenon where certain gases in the atmosphere trap heat (long-wave infrared radiation) radiating from the Earth's surface, keeping the Earth warm.

Responsible Gases and Sources:

  • Carbon Dioxide (\( CO_2 \)): Burning of fossil fuels, deforestation, respiration.
  • Methane (\( CH_4 \)): Paddy fields, guts of ruminant animals (cattle), marshes.
  • Chlorofluorocarbons (CFCs): Refrigerants, aerosols, coolants.
  • Nitrous Oxide (\( N_2O \)): Nitrogen fertilizers, burning of biomass.
Q. 23. Describe physiological effects and applications of ethylene.
Answer:

Physiological Effects:

  • Promotes ripening of fruits (climacteric fruits).
  • Stimulates abscission of leaves and flowers.
  • Breaks seed and bud dormancy.
  • Induces senescence (aging).

Applications:

  • Used artificially to ripen fruits like bananas, mangoes, and apples (e.g., Ethephon).
  • Used to initiate flowering in pineapples.
  • Used for thinning of cotton, cherry, and walnut.
Q. 24. Give the name and type of I, IV and VII cranial nerves.
Answer:
  • I (First) Cranial Nerve: Olfactory Nerve. Type: Sensory.
  • IV (Fourth) Cranial Nerve: Trochlear Nerve. Type: Motor.
  • VII (Seventh) Cranial Nerve: Facial Nerve. Type: Mixed.
Q. 25. Describe pyramid of energy with the help of diagram.
Answer:

The pyramid of energy is a graphical representation of the energy available at each trophic level in an ecosystem. It is always upright because energy is lost as heat at each transfer (according to the 10% law).

  • Base (Producers): Maximum energy.
  • Primary Consumers: Less energy than producers.
  • Secondary Consumers: Less energy than primary consumers.
  • Tertiary Consumers: Least energy at the top.
Upright Pyramid showing Producers → Herbivores → Carnivores with decreasing energy bars
Q. 26. What is lac? Enlist economic importance of Lac.
Answer:

Lac: It is a resinous substance secreted by the dermal glands of the female lac insect (Tacchardia lacca or Laccifer lacca).

Economic Importance:

  • Used in the manufacture of bangles, toys, and jewelry.
  • Used in sealing wax, polishes, and varnishes.
  • Used in electrical insulation materials.
  • Used in printing inks and mirrors.

SECTION – D

Attempt any THREE of the following questions :

Q. 27. Describe histological structure of Testis with well labelled diagram.
Answer:

The histological structure of the testis shows numerous seminiferous tubules embedded in interstitial tissue.

  • Seminiferous Tubules: Each tubule is lined by Germinal Epithelium consisting of two types of cells:
    1. Germ cells (Spermatogonia): These undergo spermatogenesis to form Primary Spermatocytes, Secondary Spermatocytes, Spermatids, and finally Spermatozoa (Sperms).
    2. Sertoli cells (Nurse cells): These provide nourishment to developing sperms.
  • Interstitial Tissue: The connective tissue between tubules contains blood vessels, nerves, and groups of Leydig cells (Interstitial cells) which secrete the male hormone Testosterone (Androgen).
Diagram: Cross Section of Testis showing Seminiferous tubules, Spermatogonia, Sperm, Sertoli cells, and Leydig cells
Q. 28. What are chromosomal disorders? Describe Turner’s syndrome and Klinefelter’s syndrome.
Answer:

Chromosomal Disorders: Disorders caused due to absence or excess or abnormal arrangement of one or more chromosomes.

Turner’s Syndrome (45, X0):

  • Cause: Absence of one X chromosome in females (Monosomy X).
  • Symptoms: Sterile females, rudimentary ovaries, lack of secondary sexual characters, short stature, webbed neck.

Klinefelter’s Syndrome (47, XXY):

  • Cause: Presence of an extra X chromosome in males (Trisomy).
  • Symptoms: Sterile males, tall stature, development of breast (Gynecomastia), feminine voice, underdeveloped testes.
Q. 29. Describe nervous system in planaria with well labelled diagram.
Answer:

Planaria (Flatworm) shows a primitive ladder-type nervous system.

  • Ganglia: A pair of cerebral ganglia (brain) is present in the head region.
  • Nerve Cords: Two longitudinal nerve cords arise from the ganglia and run backward along the body.
  • Transverse Commissures: The longitudinal nerve cords are connected by transverse nerve connectives (commissures) giving it a ladder-like appearance.
  • Sensory structures: Eye spots (photoreceptors) and auricles (chemoreceptors) are present in the head region.
Diagram: Planaria showing Eye spots, Ganglia, and Ladder-like nerve cords
Q. 30. Explain following terms :
(a) Grafting
(b) Apomixis
(c) Polyembryony
(d) Parthenocarpy
Answer:

(a) Grafting: It is a method of artificial vegetative propagation where parts of two plants are joined so that they grow as one plant. The part with roots is called 'Stock' and the part with shoot is called 'Scion'.

(b) Apomixis: It is the formation of seeds without fertilization. It mimics sexual reproduction but is a form of asexual reproduction.

(c) Polyembryony: It is the occurrence of more than one embryo in a seed. (e.g., Citrus, Mango).

(d) Parthenocarpy: It is the formation of fruit without fertilization. Such fruits are seedless (e.g., Banana, Grapes).

Q. 31. Interpret the given diagrams A and B. Enlist the changes occuring during inspiration and expiration.
Diagram A: Expiration (Ribs in, Diaphragm domed Diagram B: Inspiration (Ribs out, Diaphragm flat)
Answer:

Interpretation:

  • Diagram A: Represents Expiration (Breathing out).
  • Diagram B: Represents Inspiration (Breathing in).

Changes occurring:

Inspiration (Diagram B) Expiration (Diagram A)
External intercostal muscles contract. External intercostal muscles relax.
Ribs and sternum move upward and outward. Ribs and sternum move downward and inward.
Diaphragm contracts and becomes flat. Diaphragm relaxes and becomes dome-shaped.
Thoracic volume increases, pressure decreases. Thoracic volume decreases, pressure increases.
Air rushes into the lungs. Air is expelled out of the lungs.
Question Paper Page No. 1 Question Paper Page No. 2 Question Paper Page No. 3 Question Paper Page No. 4 Question Paper Page No. 5 Question Paper Page No. 6 Question Paper Page No. 7 Question Paper Page No. 8 Maharashtra Board Biology Question Paper
Labels: , , , , ,
Subscribe to: Posts (Atom)