Biology (56) - 2024 Solution
Maximum Marks: 70 | Time: 3 Hrs.
SECTION – A
(i) Identify the growth hormone in plants which causes inhibitory effect.
(ii) Which one of the following is not a part of lac operon?
(iii) In absence of fertilization, corpus luteum degenerates into _____.
(iv) Which of the following divides nasal cavity?
(v) Which of the following is caused by unsterilized needle?
(vi) Recognition sequence of restriction enzymes are generally _____ nucleotides long.
(vii) Which of the following types require pollinator but result is genetically similar to autogamy?
(viii) Which one of the following does not evolve further?
(ix) Identify the appropriate term for the number of births under ideal conditions :
(x) Observe the graph and select correct option :
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(i) What are vestigeal organs?
(ii) Expand the term ZIFT.
(iii) Give the name of endocrine gland which is prominent at birth but gets gradually atrophied in adult stage.
(iv) What is the full form of IAA?
(v) Give the name of microbial source of antibiotic chloromycetin.
(vi) Which cells of islets of Langerhans produce a hormone insulin?
(vii) How many meiotic divisions are required for the formation of 300 seeds in angiosperm?
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.
SECTION – B
Attempt any EIGHT of the following questions : [16]
- He carefully selected the garden pea plant (Pisum sativum) which was self-fertilizing and easy to grow.
- He studied the inheritance of one character at a time (monohybrid) before proceeding to complex crosses.
- He kept accurate statistical records of his breeding experiments.
- He was fortunate that the characters he chose were located on different chromosomes or showed no linkage.
1. Isolation of DNA
2. Restriction digestion
3. Gel electrophoresis
4. Southern blotting
| 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. |
- 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.
(a) Gene flow
(b) Chromosomal aberrations
(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.
- 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.
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.
Examples: Lichens (association between algae and fungi), Mycorrhiza (association between fungi and roots of higher plants).
- 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.
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).
[ sinusitis, emphysema, silicosis and asbestosis, laryngitis ]
(a) Breakdown of alveoli, shortness of breath.
(b) Inflammation of the sinuses, mucous discharge.
(c) Inflammation of larynx, vocal cord, sore throat, hoarseness of voice, mucous build up and cough.
(d) Inflammation of fibrosis, lung damage.
- Screening: Sewage is passed through screens or wire meshes to remove large floating debris like suspended solids, plastics, rags, etc.
- 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 : [24]
- Splicing: The introns (non-coding sequences) are removed, and exons (coding sequences) are joined together in a defined order.
- Capping: An unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of the hn-RNA.
- Tailing (Polyadenylation): Adenylate residues (200-300) are added at the 3'-end in a template-independent manner.
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.
- Specificity: It is specific to a particular pathogen or antigen. It can distinguish between different types of pathogens.
- Diversity: It can recognize a vast variety of diverse pathogens.
- Discrimination between Self and Non-self: It can differentiate between body's own cells (self) and foreign molecules (non-self).
- 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).
- 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).
- Denaturation (94-98°C): The double-stranded DNA is heated to separate the two strands by breaking hydrogen bonds.
- Annealing (40-60°C): Two sets of primers (small DNA sequences) bind (anneal) to their complementary sequences on the single-stranded DNA templates.
- 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.
- 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.
- 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.
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.
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.
- I (First) Cranial Nerve: Olfactory Nerve. Type: Sensory.
- IV (Fourth) Cranial Nerve: Trochlear Nerve. Type: Motor.
- VII (Seventh) Cranial Nerve: Facial Nerve. Type: Mixed.
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.
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 : [12]
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:
- Germ cells (Spermatogonia): These undergo spermatogenesis to form Primary Spermatocytes, Secondary Spermatocytes, Spermatids, and finally Spermatozoa (Sperms).
- 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).
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.
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.
(a) Grafting
(b) Apomixis
(c) Polyembryony
(d) Parthenocarpy
(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).
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. |