{"id":47112,"date":"2024-02-09T08:22:39","date_gmt":"2024-02-09T02:52:39","guid":{"rendered":"https:\/\/www.aplustopper.com\/?p=47112"},"modified":"2024-02-09T12:41:59","modified_gmt":"2024-02-09T07:11:59","slug":"isc-class-12-biology-previous-year-question-papers-solved-2012","status":"publish","type":"post","link":"https:\/\/www.aplustopper.com\/isc-class-12-biology-previous-year-question-papers-solved-2012\/","title":{"rendered":"ISC Biology Question Paper 2012 Solved for Class 12"},"content":{"rendered":"

ISC Biology Previous Year Question Paper 2012 Solved for Class 12<\/h2>\n

Part-I
\n(Attempt All Questions)<\/p>\n

Question 1.
\n(a) Give one difference between each of the following :
\n(i) Ventricular systole and Ventricular diastole.
\n(ii) Sertoli cells and Spermatids.
\n(iii) Dwarfism and Cretinism.
\n(iv) Antibodies and Interferons.
\n(v) Glucocorticoids and Mineralocorticoids.<\/p>\n

(b) Give reasons for the following :
\n(i) Nerve impulse travels in one direction.
\n(ii) Jamming of wooden doors and windows takes place during rainy season.
\n(iii) A cut plant wilts fast even if its cut end is dipped in water.
\n(iv) Urine excreted during summer months is hypertonic.
\n(v) A person has difficulty in focusing on nearer objects, as the age increases.<\/p>\n

(c) Give a scientific term for each of the following:
\n(i) A single isolated contraction of muscle fibre.
\n(ii) Inhibition of lateral bud growth by terminal bud.
\n(iii) Specialised structure through which guttation occurs.
\n(iv) Development of embryo from the egg without the process of fertilization.
\n(v) Process of splitting of water molecules during photosynthesis.
\n(vi) Passing out of urine.<\/p>\n

(d) Mention the most significant function of each of the following :
\n(i) Tapetum cells
\n(ii) Serotonin
\n(iii) Lenticels
\n(iv) Cerebrospinal fluid
\n(v) Islets of Langerhans
\n(vi) Bundle sheath<\/p>\n

(e) State the most significant contribution of the following scientists :
\n(i) Hans Berger
\n(ii) Dixon and Jolly
\n(iii) J.B. Lamarck
\n(iv) William Harvey<\/p>\n

(e) State the most significant contribution of the following scientists: [2]<\/p>\n

(f) Expand the following: [2]
\n(1) OP
\n(ii) RuBP
\n(iii) IBA
\n(iv) PEP
\nAnswer:
\n(a) (i)<\/p>\n\n\n\n\n
Ventricular systole<\/strong><\/td>\nVentricular diastole<\/strong><\/td>\n<\/tr>\n
Ventricles contract and the blood flows from ventricles to arteries.<\/td>\nVentricles are relaxed and the blood flows from auricles to the ventricles.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(ii)<\/p>\n\n\n\n\n
Sertoli cell<\/strong><\/td>\nSpermatids<\/strong><\/td>\n<\/tr>\n
Present in the germinal epithelium of the seminiferous tubules which provides nour\u00adishment to the developing sperms.<\/td>\nFew cells of the germinal epithelium of the seminiferous tubules undergo meiosis to produce spermatids.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(iii)<\/p>\n\n\n\n\n
Dwarfism<\/strong><\/td>\nCretinism<\/strong><\/td>\n<\/tr>\n
It is caused due to hyposecretion of growth hormone during childhood.<\/td>\nCaused due to malfunctioning of the thyroid gland in infant.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(iv)<\/p>\n\n\n\n\n
Antibodies<\/strong><\/td>\nInterferons<\/strong><\/td>\n<\/tr>\n
Acts slowly and long-lasting.<\/td>\nThe action is quick but temporary.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(v)<\/p>\n\n\n\n\n
Glucocorticoids<\/strong><\/td>\nMineralocorticoids<\/strong><\/td>\n<\/tr>\n
Influences the metabolism of carbohy\u00addrates, proteins and fats.<\/td>\nAffects the transport of electrolyte and absorption of sodium ions by the various parts of the uriniferous tubules.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(b) (i) Nerve impulse travels in one direction Since the neurotransmitter is present only in the axon terminal so nerve impulse always travels from the axon terminal of one neurone to the dendrite or cell body of the next neurone.<\/p>\n

(ii) Jamming of wooden doors and windows takes place during rainy season The cellulose of the wood absorbs water and swells up. This causes increase in size of doors and windows resulting in jam.<\/p>\n

(iii) A cut plant wilts fast even if the cut end is dipped in water As the rate of transpiration is higher than that of the absorption by the cut end, the wilting is fast.<\/p>\n

(iv) Urine excreted during summer months is hypertonic During the summer, excessive water is lost as sweating. Urine becomes hypertonic to reduce the loss of water in urine and maintains the osmotic concentration of the blood constant.<\/p>\n

(v) A person has difficulty in focusing on nearer objects as the age increases With the advancement of age, the elasticity of the lens decreases. It causes the person difficult to focus the nearer object.<\/p>\n

(e)
\n(i) Single muscle twitch
\n(ii) Apical dominance
\n(iii) Hydathodes
\n(iv) Parthenocarpy
\n(v) Photolysis
\n(vi) Micturition<\/p>\n

(f)
\n(i) Tapetum cells: Rich in food materials, surrounds the microspore mother cell and supplies food to the developing spores.
\n(ii) Serotonin : Acts as a neurotransmitter.
\n(iii) Lenticels : Allows exchange of gases between the atmosphere and the interior of the cells.
\n(iv) Cerebrospinal fluid : Forms the protective cushion over the brain and spinal cord against shock and mechanical injury.
\n(v) Islets of Langerhans: Secrete two hormones –<\/p>\n

(a) insulin and
\n(b) glucagon
\n(vi) Bundle sheath : Surrounds the vascular bundles in monocot leaf, provides mechanical support.<\/p>\n

(e)
\n(i) hans Berger : First to record EEG
\n(ii) Dixon and Jolly: Theory of ascent of sap
\n(iii) J. B Lamarck: Theory of inhentance of acquired characters.
\n(iv) William Harvey : Discovered closed circulatory system<\/p>\n

(f)
\n(i) OP – Osmotic pressure\/potentiaL
\n(ii) RuBP \u2014 Ribulose biphosphate
\n(iii) IBA – Indole – 3 – butyric acid
\n(iv) PEP \u2014 Phosphoenol pyruvic acid<\/p>\n

Part-II
\nSection – A
\n(Attempt any three questions)<\/p>\n

Question 2.
\n(a) Give any four anatomical differences between monocotyledonous and dicotyledonous leaf. [4]
\n(b) Explain the phases of growth in the meristem of plants. [3]
\n(c) Draw a neat labelled diagram of a matured anatropous ovule before fertilization. [3]
\nAnswer:
\n(a) MonocoG\u2019ledonous\/Isobilateral Leaf<\/p>\n

    \n
  1. Both the surfaces are alike.<\/li>\n
  2. Stomata are equally distributed on both sides. Mesophyll undifferentiated.<\/li>\n
  3. Vascular bundles are partially or completely surrounded by a sclerenchymatous sheath.<\/li>\n
  4. Vascular bundles have phloem on the upper side and xylem on the lower side.<\/li>\n<\/ol>\n

    Dicotyledonous\/Dorsiven frai leaf<\/p>\n

      \n
    1. Distinct upper and lower surface.<\/li>\n
    2. Stomata are mostly present on the lower side. Mesophyll differentiated.<\/li>\n
    3. Vascular bundles has sclerenchymatous patches on the upper side.<\/li>\n
    4. Vascular bundles have downward phloem and upward xylem.<\/li>\n<\/ol>\n

      (b) Phases of growth in meristem of plant:
      \n(i) Cell formation phase – During this phase meristematic cell divides to form new cells. The newly formed cells are thin wailed.
      \n(ii) Cell enlargement phase – During this phase, the newly formed cells absorb water by osmosis resulting in the increase in turgidity and expansion and dialation of the elastic cell wall.
      \n(iii) Cell differentiation phase – This occurs below the zone of elongation. The thin cell wall grows in thickness and the cells gradually undergoes structural and physiological changes.<\/p>\n

      \"ISC<\/p>\n

      Question 3.
      \n(a) Give an account of activity of cambium in the secondary growth of the stem. ‘
      \n(b) Write three differences between C3<\/sub> and C4<\/sub> cycles.
      \n(c) Mention two advantages each of the following :
      \n(i) Hydroponics\u2019
      \n(ii) Turgidity to plants
      \n(iii) Cross-pollination
      \nAnswer:
      \n(a) Activity of cambium in the secondary growth of the stem –
      \n1. F ormation of cambium ring – The vascular bundles of dicot stem have strips of cambium in between xylem and phloem. During secondary growth, the cells of medullary rays in a line with this cambium develop meristematic activity and forms strips of cambium. The intra and interfascicular cambium unites to form cambium ring or phellogen.<\/p>\n

      2. Formation of secondary tissue – The cambium ring becomes active as a whole and starts cutting off new cells. The cut off cells of the outer side get differentiated into phloem and are called secondary phloem. The cut off cells of the innerside are modified into secondary xylem. The activity of the cambium ring is more on the innerside than on the outerside which results in the increase of the xylem more rapidly than the phloem.<\/p>\n

      3. Secondary medullary ray – Certain cells of the cambium form some narrow bands of living parenchyma cells-passing through secondary xylem and secondary phloem and are called secondary medullary rays. This provides radial conduction of food from the phloem and water and mineral salts from the xylem.<\/p>\n

      4. Annual Ring – Activity of cambium is not uniform in those plants which grows in the regions where favourable climate conditions regularly alternates with the unfavourable conditions. The cambium is more active in spring and less active in winter. The wood formed in the spring is known as spring wood and that formed in summer and winter is known as autumn wood. The two woods appear together in concentric rings in the trunk and is known as annual ring. The age of the plant is approximately calculated by counting the number of annual rings.<\/p>\n

      (b) C3<\/sub> cycle<\/p>\n

        \n
      1. RuBP is the CO2<\/sub>\u00a0acceptor.<\/li>\n
      2. PGA is the first stable product.<\/li>\n
      3. The process runs at a optimum temperature of 1O\u00b0C\u201425\u00b0C.<\/li>\n<\/ol>\n

        C4<\/sub> cycle<\/p>\n

          \n
        1. PEP is the first carbon dioxide acceptor.<\/li>\n
        2. Oxaloacetic acid is the first stable product.<\/li>\n
        3. The process runs at a optimum temperature of 30\u00b0C to 45\u00b0C.<\/li>\n<\/ol>\n

          (c) Two advantages of the following –
          \n(i) Hydroponics :
          \n(a) No soil required for growing the plants hence useful in infertile and dry soil.
          \n(b) Plants are free from soil pathogens and weeds.<\/p>\n

          (ii) Ttirgidity to plants:
          \n(a) Provides mechanical supports to non-woody parts of the plant.
          \n(b) Regulates the opening and closing of the stomata.<\/p>\n

          (iii) Cross-pollination:
          \n(a) New varieties with useful characters are produced.
          \n(b) Results in healthy and stronger offsprings.<\/p>\n

          Question 4.
          \n(a) Explain the movement of water cell to cell across the root from the soil to the xylem. [4]
          \n(b) Draw a labelled diagram of T.S of hyaline cartilage. Write a brief note on its functions. [3]
          \n(c) What is the full form of ADH? How does ADH control osmoregulation in human kidney? [3]
          \nAnswer:
          \n(a) Root hairs are in contact with soil particles. These provide a large surface area for water absorption. Water diffuses into the root hairs as a result of diffusion pressure deficit gradient. Water enters as long as the DPD of the cell sap is greater. The DPD falls following an increase in TP. The DPD of the adjoining cortical cells being higher and water moves from root hairs into cortical cells.
          \n\"ISC<\/p>\n

          The DPD of the next inner cells being higher, water moves into them. In this way, water moves from one cortical cell to the other along a DPD gradient till it reaches the passage cells in the endodermis. Through the radial and inner tangential walls of the passage cell water enters the pericycle and then to the protoxylem element.<\/p>\n

          (b) Hyaline cartilage – The matrix is homogeneous, translucent and fibreless and some what elastic. It forms the embryonic skeleton invertebrates and the skeleton of elasmobranch fishes.<\/p>\n

          Fig. Hyaline cartilage<\/p>\n

          (c) ADH- Antidiuretic hormone It is released from the posterior part of the pituitary gland. It acts on distal convoluted tubules and collecting ducts of nephron and increase their permeability for water. The secretion of ADH varies with the intake of water. If less water is taken more ADH is produced to reduce the urine volume and when more water is taken less ADH is produced so that only small amount of water is reabsorbed and majority goes out in the urine.<\/p>\n

          Question 5.
          \n(a) Explain the process of oogenesis in humans. [4]
          \n(b) State three differences between red muscle fibre and white muscle fibre. [3]
          \n(c) Mention a cause and symptom of each of the following : [3]
          \n(i) Emphysema
          \n(ii) Renal calculi
          \n(iii) Diarrhoea. [2]
          \nAnswer:
          \n(a) Oogenesis occurs in the germinal epithelium cells of the ovary resulting in the formation of a mature ovum.
          \nThe process is divided into –
          \n(i) Multiplication phase – Oogonia multiply by mitotic division forming primary oocytes.
          \n(ii) Growth phase – Long phase, extend over many years primary oocyte grows into large size.
          \n(iii) Maturation phase – Primary oocyte undergoes two maturation divisions to form a single ovum and two polar bodies.
          \n\"ISC<\/p>\n

          (b) Red muscle fibre:<\/p>\n