Part-I (20 Marks)<\/p>\n
Question 1.
\n(a) Give a brief answer for each of the following : [4]
\n(i) What is central dogma?
\n(ii) Define cryopreservation.
\n(iii) What is symbiosis?
\n(iv) Explain the term perianth.<\/p>\n
(b) Each of the following question(s) \/ statement(s) has four suggested answers. Choose the correct option in each case. [4]
\n1. The curve showing the amount of light absorbed at each wavelength is :
\n(i) Action spectrum
\n(ii) Absoiption spectrum
\n(iii) Quantum yield
\n(iv) Quantum requirement<\/p>\n
2. After fertilisation, the integuments of an ovule develop into :
\n(i) Seed
\n(ii) Seed coat
\n(iii) Fruit
\n(iv) Fruit wall<\/p>\n
3. Meselson and Stahl\u2019s experiment proved:
\n(i) Transduction
\n(ii) Transformation
\n(iii) DNA is the genetic material
\n(iv) Disruptive DNA replication<\/p>\n
4. The act of expelling the full-term foetus from the uterus is termed as :
\n(i) Gestation
\n(ii) Implantation
\n(iii) Parturition
\n(iv) Capacitation<\/p>\n
(c) Give scientific terms for each of the following: [4]
\n(i) The smallest unit of DNA which can mutate.
\n(ii) Type of water absorption by roots where metabolic energy is required.
\n(iii) Statistical study of human population.
\n(iv) Multiple effects of a gene on the phenotype of an organism.<\/p>\n
(d) Expand the following abbreviations : [4]
\n(i) rDT
\n(ii) BAC
\n(iii) SSBP
\n(iv) IUCD<\/p>\n
(e) Name the scientists who have contributed to the following : [4]
\n(i) Reverse transcription
\n(ii) Photorespiration
\n(iii) Principle of limiting factors
\n(iv) Photolysis of water
\nAnswer:
\n(a) (i) The basic belief held by molecular geneticists that the flow of genetic information is unidirectional and occurs from DNA \u2192 RNA \u2192 Protein.
\n(ii) Cryopreservation is a technique in which organisms, tissue and cells are preserved and stored at very low temperature of liquid nitrogen (-196\u00b0C) for years. They remain viable in frozen state for future use.
\n(iii) Symbiosis is a beneficial association between members of different species in which both the partners are benefitted.
\n(iv) Perianth is the term used when the calyx and corolla of the flower are indistinct.<\/p>\n
(b)
\n1. – (ii) Absorption spectrum
\n2. – (ii) Seed coat
\n3. – (iii) DNA is the genetic material
\n4. – (iii) Parturition<\/p>\n
(c) (i) Muton
\n(ii) Active absorption
\n(iii) Demography
\n(iv) Pleiotropy<\/p>\n
(d) (i) recombinant DNA Technology
\n(ii) Bacterial Artificial Chromosome
\n(iii) Single-Strand Binding Protein
\n(iv) Intra-Uterine Contraceptive Device<\/p>\n
(e) (i) Temin and Baltimore
\n(ii) Dicker and Tio
\n(iii) Blackman
\n(iv) Robin Hill<\/p>\n
Part-II (50 Marks)
\nSection-A
\n(Answer any two questions)<\/p>\n
Question 2.
\n(a) Mention three features of the Neanderthal Man. [3]
\n(b) Differentiate between connecting link and missing link. [1]
\n(c) What is adaptive radiation? [1]
\nAnswer:
\n(a) (i) Brain size 1300-1600 cc.
\n(ii) Used hides to protect the body
\n(iii) Buried their dead
\n(iv) Knew use of fire, lived in caves
\n(v) Omnivore.<\/p>\n
(b) Connecting links are living intermediate forms which possess characters of two groups. Missing links are the transitional or intermediate forms between two groups of organisms which occur only in the fossil state.<\/p>\n
(c) Adaptive radiation is the formation of a number of divergent species from a common ancestor with new species adapting to different ecological niches.<\/p>\n
Question 3.
\n(a) Give an account of Lederberg\u2019s replica plating experiment to show the genetic basis of evolution. [3]
\n(b) Define phylogeny. [1]
\n(c) What is Founder s effect? [1]
\nAnswer:
\n(a) Lederberg\u2019s Replica Plating Experiment: Joshua Lederberg and Esther Lederberg, gave an experimental demonstration of genetic basis of adaptation. They performed an experiment on bacteria to demonstrate the genetic basis of a particular adaptation. They obtained a \u2018master plate\u2019 of bacterial culture by inoculating a dilute suspension of bacteria on an agar plate. After a certain period, the master plate was found to contain several bacterial colonies. Each colony represented a clone that has originated from a single bacterial cell as a result of repeated divisions. They prepared many replicas of the master plate on new agar plates. After that, they tried to grow bacteria on replica plates with an antibiotic (e.g., penicillin). Most colonies of the master plate failed to grow on replica plates having antibiotic. Only few colonies that could be formed were found to be resistant to penicillin. It means that certain bacteria have acquired an ability to survive and grow in a new environment. This mutant strain of bacteria has adapted.<\/p>\n
According to Darwinism, the original suspension of bacterial cells contained few mutant bacteria which had mutant genes that enabled them to survive the effect of penicillin and form colonies.
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<\/p>\n
(Sensitive colony) (Resistant colony)
\nFig. Lederberg\u2019s replica plating experiment<\/p>\n
The Lederberg\u2019s replica plating experiment provided a support to Darwinism is that the adaptation in bacterial cells arose due to selection of pre-existing mutant forms of bacteria. It is based on the fact that the pattern of colonies seen in all the replica plates was same.<\/p>\n
(b) Phylogeny deals with the study of evolutionary history of an individual\/group of organisms.<\/p>\n
(c) From the original drifted population, some organisms are selected and colonise in the new habitat, (founders), produce different alleles (due to mutations) resulting rapid changes in the phenotypes forming new species, is called founder effect.<\/p>\n
Question 4.
\n(a) With reference to the levels of organisation, differentiate between living organisms and non-living objects. [3]
\n(b) Mention one cause for variation in nature. [1]
\n(c) What is the difference between the teeth of apes and the teeth of man? [1]
\nAnswer:
\n(a) Organisation is a systematic arrangement of smaller and simpler components into larger one in a hierarchy or pyramid of levels where each level is formed of components of lower level and itself becomes part of higher-level for achieving a common goal.<\/p>\n
Three levels of organisation are met in nature – physical biological and ecological. At every level two types of questions arise – how (mechanism of process) and why (significance of the process).
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The non-living objects occur as molecules and compounds which are found as mixture, colloids and crystals. They are formed of atoms, atoms are formed of subatomic particles, which are ^ composed of electrons, protons and neutrons the lowest structures.<\/p>\n
In living organisation, the molecules and g compounds polymerise and aggregate to form o\u2019 biomolecules. The different biomolecules aggregate and organise to form different subcellular structures (= organelles) which together constitute the first living component the cell (individual unicellular organism). The cells may be held together to form tissue and different tissues together form organ.<\/p>\n
The different organs constitute a organ system \u00a7 and different organ systems form a multicellular \u00b1 complex whole Called individual organism the basic unit of ecology. if An aggregation of individual of same species is m called population. The assemblage of population of different species present is an area is called Biological Community.<\/p>\n
The different biological communities and the physical environment both get integrated to form a self-sufficient, self-regulated fragment of nature, called ecosystem.<\/p>\n
The different ecosystems characterised by specific climatic zone, form a major category of regional gecological organisation called Biome. Biomes are of two types-terrestrial and aquatic.<\/p>\n
(b) One major cause of variation in nature is s environment. The environment by its components a. the temperature, light, nutrition, water and medicine bring about non-inheritable changes called modification or acquired characters. These variations affect the somatic or body cells of the organism.<\/p>\n
(c) (i) In apes, incisors are large whereas in humans incisors are small.
\n(ii) Canines are large and projecting in apes while in humans canines do not project beyond the level of other teeth.<\/p>\n
Section-B
\n(Answer any two questions)<\/p>\n
Question 5. (ii) Formation of secondary tissues : The fusiform cell of cambial ring becomes active and starts cutting off new cells. The cells cut off on the outer side get differentiated into secondary phloem and are called secondary phloem. The cells cut off on the inner side form the elements of xylem which constitute secondary xylem. The secondary phloem consists of sieve tubes, companion cells, phloem fibres and phloem parenchyma. Secondary xylem consists of pitted vessels, tracheids, xylem fibres, xylem parenchyma.<\/p>\n The cells of vascular cambium are of two types, elongated spindle-shaped fusiform initials and shorter isodiametric ray initials. Both appear rectangular in TS. Ray initials give rise to<\/p>\n Fig. A, Complete ring of vascular cambium formed by strips of intrafascicular cambium and interfascicular cambium; B, L.S. Vascular cambium showing fusiform and ray initials; C, formation of secondary vascular tissue mother cells; D, the beginning of secondary growth (mostly made-up of secondary vascular tissues) of dicot stem (diagrammatic); E, two-year stage of secondary growth of a dicot stem.<\/p>\n (iii) Secondary medullary rays: Ray initial cells of cambium form radially elongated narrow bands of living parenchyma cells passing through secondary xylem and secondary phloem and are called secondary medullary rays. The part of ray in secondary xylem is called xylem ray and the part present in secondary phloem is called phloem ray. These provide radial conduction of food from the phloem and water, mineral salts from xylem.<\/p>\n (iv) Annual rings : Activity of cambium is not uniform in those plants which grow in the regions where favourable climatic conditions (spring or rainy season) alternate regularly with unfavourable climatic conditions (cold winter or dry hot summer). In temperate climates, cambium becomes more active in spring and forms greater number of vessels with wider cavities while in winter it becomes less active and forms narrower and smaller vessels. The wood formed in the spring is called spring wood and that formed in dry summer or cold winter, autumn wood. These two woods appear together in the form of a concentric ring, in the transverse section of the trunk and this is known as annual ring i.e., the total wood (secondary xylem) produced in a year. The growth of successive years appears in the form of concentric or annual rings, each annual ring representing the year\u2019s growth. The age of the plant can approximately be determined by counting the number of annual rings (Dendrochronology).<\/p>\n (c) Advantages of Vegetative Propagation : Question 6. (i) Pituitary hormones : The pituitary hormones secreted during menstrual cycle are FSH and LH. The FSH (Follicular stimulating hormone) stimulates the growth of primary oocyte into secondary oocyte and the Graafian follicle.<\/p>\n The maximum level of LH (Luteinising hormone) induces rupture of Graafian follicle to release ovum containing secondary oocyte (ovulation).<\/p>\n (ii) Ovarian hormones : The FSH secretion by pituitary gland stimulates the ovarian follicles to secrete oestrogen. Oestrogen stimulates the proliferation of endometrium of the uterine wall. After ovulation, the remaining cells of ovarian follicle are stimulated by LH to develop corpus luteum which secretes large amount of progesterone. Progesterone is essential for maintenance of endometrium, for implantation of fertilised ovum and other events of pregnancy. .<\/p>\n (b) Adaptation for wind-pollination or anemophily : (c) Differences between Sapwood or Alburnum and Heartwood or Duramen<\/p>\n
\n(a) Give a graphic representation of the C3<\/sub> cycle. [4]
\n(b) Discuss the role of cambium in secondary growth of dicot stems. [4]
\n(c) State two advantages of vegetative propagation. [2]
\nAnswer:
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\n(b) Secondary growth is the characteristic of dicot stem because of the presence of open vascular bundles in stem \u2014 Activity of the Cambium :
\n(i) Formation of cambium ring: The vascular bundles of a dicot stem have strips of cambium in-between xylem and phloem which are known as intrafascicular cambium. During secondary growth, the cells of medullary rays at the level of intrafascicular cambium become meristematic activity and form strips of cambium called interfascicular cambium. The intra and interfascicular cambium join to form a complete ring called cambial ring or phellogen. The cells of vascular cambium are of two types, elongated spindle-shaped fusiform initials and shorter isodiametric ray initials. Both appear rectangular in TS. Ray initials give rise to vascular rays. The activity of cambial ring gives rise to secondary growth.’<\/p>\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/ISC-Class-12-Biology-Previous-Year-Question-Papers-Solved-2016-5.png\")
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<\/p>\n
\n(i) It is the only known method of multiplication in seedless varieties and species, eg., Banana, Sugarcane.
\n(ii) It is a quick method of multiplication.
\n(iii) It helps in rapid spread of plant over an area.
\n(iv) Good qualities of the race or variety can be preserved indefinitely.<\/p>\n
\n(a) Explain the role of hormones during the menstrual cycle.
\n(b) Give four adaptations shown by flowers pollinated by wind.
\n(c) Give two differences between heartwood and sapwood.
\nAnswer:
\n(a) Menstruation phase occurs when the concentration of ovarian and gonadotropin hormones is low in blood. Reduced concentration of these hormones stimulates the hypothalamus to produce GnRH (gonadotropin-releasing hormone). It activates anterior pituitary to gonadotropin hormones.<\/p>\n
\n(i) Flowers small inconspicuous.
\n(ii) Calyx, corolla reduced or absent.
\n(iii) Flowers colourless, nectarless or odourless.
\n(iv) Flowers produced above and before foliage, in case of unisexual flowers, male flowers are abundant to compensate loss and to ensure the pollination.
\n(v) Stamens and stigma (feathery) exserted and well exposed.
\n(vi) Pollen grains, light, small, dusty, non-sticky or winged (Pinus).
\n(vii) Pollen grains dry and unwettable, e.g., maize, grasses, Urtica.
\n(viii) Number of ovules very less, often single. (any four points)<\/p>\n
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