ISC Biology Previous Year Question Paper 2013 Solved for Class 12
(Attempt All Questions)
(a) Give one significant difference between each of the following : 
(i) Implantation and Parturition.
(ii) Active absorption and passive absorption.
(iii) Haemodialysis and Peritoneal dialysis.
(iv) Simple Suit and Aggregate fruit.
(v) Auricles and Ventricles.
(b) Explain what would happen if: 
(i) Excess fertilizers are added to the soil.
(ii) Blood clots in the coronary artery.
(iii) Beta cells in the islets of Langerhans are damaged.
(iv) Silicon emulsion is applied over the surface of leaves.
(v) Magnesium element is deficient in the soil.
(c) Each of the following questions/statements have four suggested answers. Rewrite the correct answer in each case: 
(i) The cell division in the tunica region of shoot apex is:
(ii) The dark coloured dead wood present in the central region of old trees is :
(iii) Dwarfism accompanied by mental retardation is due to hypo-secretion of:
(A) Growth hormone
(B) Thyroxine hormone
(D) Adrenalin hormone
(iv) Oxygen is released in photosynthesis by:
(B) Photolysis of water
(v) The spinal nerve is:
(A) A mixed nerve
(B) A sensory nerve
(D) A cranial nerve
(vi) The cells of the areolar tissue which produce heparin are:
(B) Mast cells
(d) Mention the most significant function of the following :
|It is the attachment of blastocyst in the endometrium of the uterus.||It is the act of expelling out of full-term foetus from the uterus at the end of gestation.|
|Active absorption||Passive absorption|
|Water is absorbed against DPD gradient, using metabolic energy.||Water is absorbed along the gradient or due to force developed by transpiration pull.|
|Simple fruit||Aggregate fruit|
|These are formed from a single simple carpel or more but fused carpels of a flower.||It develops from several ovaries of free carpels of a flower.|
(b) (i) Excess fertilizers will form a hypertonic solution in the soil. Exosmosis will then occur in the root hair cells resulting in plasmolysis ultimately the plant will die due to loss of water.
(iv) Silicon emulsion over the surface of leaves will block the stomata and hence stomatal and cuticular transpiration will be reduced.
(c) (ii) The dark coloured dead wood present in the central region of the old tree is heartwood.
(iv) Oxygen is released in photosynthesis by photolysis of water.
(d) (iii) Parenchyma remains turgid and helps to provide mechanical support and maintains the shape of the plant body. They play an important role in the storage of food and wound recovery and regenerate.
(v) Guard cells regulate the opening and closing of stomata.
(e) (i) Munch – gave the Mass Flow Hypothesis.
(ii) Ronald Ross – described the life cycle of Plasmodium in the mosquito.
(iii) Gave Hall’s process.
(iv) Introduced the term ‘New systematics’.
(f) (ii) Follicle Stimulating Hormone.
(iii) Acquired Immuno Deficiency Syndrome.
(iv) Dichloro diphenyl trichloroethane.
Part-II (50 Marks)
(Answer any three questions)
(a) Give four differences between root apex and shoot apex.** 
(b) Explain the development of the different types of endosperms in angiosperms. 
(c) Explain briefly : 
(i) Capillary water
(b) Formation of endosperm is initiated by mitotic division of primary endosperm nucleus, which is triploid and is formed by triple fusion of two polar nuclei or secondary nucleus (2n) with male gamete (n). Endosperm is formed before the division of zygote.
In angiosperms, endosperm development is of the three types :
(i) Nuclear type : It is the most common type of endosperm formation. In this type, the primary endosperm nucleus divides repeatedly and gives rise to a number of free nuclei which remain as peripheral layer and a large central vacuole appears in the embryo sac. Cell wall formation takes place later leading to the formation of cellular endosperm e.g., Coconut, Areca. In coconut, central part remains free nuclear.
(ii) Cellular type : In this type, first and subsequent divisions of primary endosperm nucleus are accompanied by wall formation, hence endosperm is cellular from the very beginning e.g., Petunia, Datura.
(iii) Helobial type : It is an intermediate type between the nuclear and cellular types. The first division of endosperm nucleus is followed by wall formation but the subsequent divisions are free nuclear. The chamber towards the micropylar end of embryo sac is much larger. A large number of nuclei are formed in it by free nuclear divisions while the nucleus of chalazal chamber divides to form a fewer, free nuclei or may not divide at all e.g., Drimya.
(c) (i) Capillary water is present in the spaces between the soil particles as a thin film. It is readily available to plants. It is held in the soil against the forces of gravity.
(ii) Osmosis is the process in which water molecules move through a semi-permeable membrane from their higher concentration to their lower concentration.
(iii) In aeroponics, roots of plant are suspended into a plastic vessel and sprayed with oxygenated nutrient rich water. This technique allows the roots to absorb nutrients much faster causing rapid growth and more yield.
(a) Explain the C4 cycle of photosynthesis. 
(b) State three advantages and three disadvantages of vegetative reproduction. 
(c) Mention one role and one deficiency symptom of the following elements in plant nutrition.** 
(a) Steps involved in C4 pathway of photo synthesis : This pathway mostly takes place in monocot plants and in some dicot plants. In this pathway, the first product of CO2 fixation is a 4 carbon compound, oxaloacetic acid hence it is called C4 pathway.
The anatomy of leaves of C4 plants is different from leaves of C3 plants (Calvin cycle). Pali-sade cells are absent in the mesophyll tissues. There is bundle sheath around the vascular bundles. In the bundle sheath cells, large chloroplasts without grana or less developed grana are present whereas in mesophyll cells, there are similar chloroplasts with well-developed grana. This type of anatomy is called Kranz anatomy.
In C4 pathway, CO2 absorbed from the atmosphere is accepted by phosphoenol pyruvic acid present in the chloroplast of mesophyll cells, leading to the formation of a 4 carbon compound oxaloacetic acid. This is converted into malic acid (4 carbon compound) which enters into the chloroplast of bundle sheath cells. Here the malic acid dissociates into pyruvic acid and CO2. Pyruvic acid re-enters mesophyll cells and regenerates phosphoenol pyruvic acid. CO2 after reacting with RuBP gives rise to sugars and other carbohydrates in bundle sheath cells according to the Calvin cycle. There is no photo-respiration in these plants.
(b) Advantages of vegetative propagation :
- Plants produced by vegetative reproduction are genetically similar to parental type. Thus, the best varieties of potatoes, oranges, apples, etc., can be preserved by vegetative reproduction without loss of their fine quality. In this way, pure lines of desired types can be selected and propagated all over the world.
- This is quick method and by this method flowers and fruits can be produced early.
- This is more sure method of producing new plants than that of seed reproduction.
- It is more economical for the plant because no energy is wasted in producing large and showy petals, nectar, fruits, seeds, etc. as in sexual reproduction.
Disadvantages of vegetative propagation :
- Due to overcrowding of large number of plants near the parent plants, there is severe competition between the members of the same species. Thus, many plants become weak and stunted.
- Over the time there may be degeneration of species due to lack of sexual stimulus.
- Due to absence of genetic Variability in vegetative reproductive structure, there may not be evolution of new species.
** Answer is hot given d.c to cha.e In the present syllabus.
(a) What are tropic hormones? Describe the feedback control of tropic hormones with an ex-ample. 
(b) Explain the conduction of nerve impulse through a nerve fibre. 
(c) Draw a labelled diagram of the T.S. of bone. ‘ 
(a) Explain the role of pancreas in digestion of various food materials.** 
(b) Briefly describe the stages in clotting of blood.** 
(c) Define: 
(i) Reparative regeneration**
(c) (ii) Before fertilizing the ovum, the sperm prepares itself for the act of fertilization and undergoes many changes. These changes in a sperm just prior to fertilization are called capacitation.
(iii) It is the onset of menstruation in a young female at the age of about 12-13 years.
(a) State four differences between transpiration and guttation. 
(b) Give an account of the secretory phase of menstrual cycle. 
(c) Define: 
(i) Radial vascular bundle
(ii) Rigor mortis**
(iii) Root pressure
- Water is lost in the form of vapours.
- It mainly occurs through the stomata.
- Only pure water is lost out.
- Mostly it occurs during the day when stomata are open in light.
- Water is lost in liquid form.
- It occurs through the hydathodes.
- Water moving out contains minerals dissolved in it.
- It occurs at night or early morning hours.
(b) Secretory Phase : The secretory phase of the menstrual cycle extends from 12-14 days. The production of LH continued in secretory phase in which a yellowish body called the corpus luteum is developed from empty ruptured follicle. Progesterone released by corpus luteum together with estrogen produced by the ovaries, produces changes in the secondary sex organs to prepare the body for pregnancy. Since these changes are due to the progesterone, this phase is also known as progesterone phase or luteal phase. Secretory phase is associated with following changes in uterus and ovary.
(1) Changes in uterus : In this phase, thickness of endometrial progressively increases. The arteries of the endometrium become coiled and glycogen content of the endometrial epithelium increases. Towards the end of the secretory phase, the endometrium is thick, soft and richly supplied with .blood. These changes are the obvious preparation for providing a suitable environment for fertilized ovum. The uterine glands become active and are filled with secretions and uterine movements are reduced so that uterus may not contract. However, in the absence of pregnancy, these measures are abortive.
(2) Changes in ovary : In case, the ovum is not fertilized, progesterone level decrease as the corpus luteum undergoes degeneration and the thickened endometrium is shed in the form of a menstrual flow and once again initiating the menstrual cycle.
(c) (i) In this type of vascular bundles, xylem and phloem occur alternately on different radii e.g., in roots.
(iii) Root pressure is the pressure exerted by the liquid contents of the fully turgid cortex cells of the root, forcing some of it into the xylem vessels and up through the stem. It is a vital phenomenon and depends upon the activity of the living cells of root.
Section – B
(Answer any two questions)
(a) Differentiate between apes and man with respect to the following characteristics : 
(iii) Brow ridges
(b) Define: 
(i) Vestigial organs
(c) Give three differences between Natural Selection and Artificial Selection.
- Posture – Semi erect
- Cranium – flattened with cranial capacity under 650 cm3.
- Brow ridges – Prominent.
- Locomotion-walk semi-erect on the outer edges of the feet and knuckles of hands, soles do not lie flat on the ground.
- Fully erect.
- Rounded with a cranial capacity of about 1450 cm3.
- Brow ridges-inconspicuous.
- Walk fully erect on the soles of feet which lie flat on the ground while walking.
(b) (i) Vestigial organs are the organs which are non-functional in the possessor but were functional in their ancestors and in related animals. It is evidence of organic evolution. e.g. in human eye, nictitating membrane, vermiform appendix.
(ii) Variation is a process by which closely related organisms come to differ amongst them-selves. Genetic drift, mutation, recombination, gene flow, migration, selection are some sources of variation.
(iii) According to Neo-Darwinism adaptations are caused due to many forces, natural selection being one of them and that characters are not inherited as such but there are character determiners which control their development.
- Nature selects the best or most’ favourable adaptation.
- It causes great diversity in nature.
- It takes hundreds of years for a new species to evolve.
- Man selects the characteristics it desires in an organism.
- It has led to the evolution of a few economically important plants and animals only.
- It leads to the formation of new species within a few months or years.
(a) State four characteristics of the Cro-Magnon man. , 
(b) Explain the basic postulates of Darwinism. 
(c) Archaeopteryx is a connecting link between reptiles and birds. Justify the statement by giving two characteristics of each group. 
(a) Cro-Magnon man or Homo sapiens fossils lived about 50,000 years ago and became extinct about 20,000 years ago.
It’s characteristic features are :
- Height was about 180 cm with sturdy body.
- Cranial capacity was about 1666 cm3.
- Face was perfectly orthognathous with a narrow, and elevated nose, arched and broad forehead, moderate brow ridges.
- Jaws were strong with man-like dentition and a well-developed chin.
- He was a cave dweller and hunter.
- He knew the art of painting and carving. He made tools and carved ornaments from ivory, made finely chipped stone arrows and spearheads.
- Used animal skin to sew crude garments.
- Used fire.
- Had some religious beliefs and elaborate burial customs.
- He neither practised agriculture nor animal domestication.
(b) Basic postulates of Darwinism :
(i) Enormous Power of Fertility : Every living organism has the power to reproduce rapidly. Hence there is a danger of population explosion, causing the shortage of the food and other facilities. As a result, there are chances of elimination of a number of individuals because the available resources are less and that resulted in competition among organisms where every individual tries to be fit better than the other. Darwin suggested that population of each species remains more or less constant because most of off springs die before themselves becoming capable of reproducing.
(ii) Struggle for Existence : Overpopulation resulted in struggle which Darwin called the struggle for existence.
It is of three types :
(a) Intra-specific Struggle : The struggle within the species.
(b) Inter-specific Struggle : The struggle between different groups of animals, e.g. carnivorous animals eat the lower herbivore animals.
(c) Environment Struggle : Struggle with the adverse environment conditions. Such as extreme temperature, lack of sunlight, water, nutrients, etc.
(iii) Variations and Heredity : During competition, every individual tries to survive and become better fitted and shows variation. But all the variations are not significant from evolutionary point of view-some may be useful and some harmful. The useful variations are inherited in progeny of those organisms in which they arose and, therefore, the progeny have better chances of survival.
(iv) Survival of the Fittest or Natural Selection : During struggle for existence, only useful variations are selected by the organisms, and are adopted. Darwin stated that the variations are sorted out and selected naturally. Therefore, the organisms which possess such selected variations are said to be fittest.
(v) Origin of Species : Due to above facts, Darwin concluded that the struggle for existence leading to the survival of the fittest tend to successive generations to become better adapted to their environment. Thus, these forms are identified as new species.
(c) Reptile-like characteristics of Archaeopteryx :
- Tail was long with free caudal vertebrae.
- Teeth present in jaws.
- A weak and keel-less sternum.
Bird-like characters of Archaeopteryx :
- Presence of feathers on the body.
- Forelimbs modified into wings.
- Four toes in the foot adapted for perching.
(a) Persons suffering from G-6PD deficiency are resistant to malaria. Explain. 
(b) Define: 
(i) Genetic Erosion
(c) Define Biofortification. 
(a) G-6PD is an enzyme glucose 6 phosphate dehydrogenase which decomposes H2C2 formed during metabolism. The deficiency of this enzyme is an inborn error of metabolism controlled by specific gene. When persons suffering from malaria are given Primaquine it causes haemolysis because H2O2 produced during metabolism is not decomposed due to the deficiency of G-6PD enzymes. This H2O2 haemolysis the blood. The haemoglobin of haemolysed blood collects on cell membrane and RBC’s are deformed. In such distorted RBC’s, malarial parasite fails to survive and multiply. It means persons suffering from G-6PD deficiency are resistant to malaria. Such persons are, therefore, favoured by natural selection in area infested with malarial parasite. For this reason, G-6PD deficiency is found in 50% Negroes living in areas with malarial infection in African countries.
(b) (i) Genetic erosion is the loss of genes from gene pool due to deforestation, urban expansion, damage to ecosystem, etc.
(ii) Bioinsecticides are living organisms like other insects, bacteria etc., which themselves or their products are used to control insect pests.
(iii) Antigen is a substance which when introduced into a vertebrate body, provokes an immune response leading to acquired immunity.
(iv) Psychosis is a kind of mental illness in which the person has no idea about his condition, loses contact with reality and cannot function in society.
(c) Biofortification is the process of breeding staple crops to have higher levels of essential nutrients such as vitamins and minerals either through selective breeding or genetic modification. e.g., biofortification of wheat with zinc.
(a) List the activities of Community Health Services.**
(b) Give three early diagnostic symptoms of cancer.
(i) Carrying capacity
(b) Early diagnostic symptoms of cancer are :
- Painful and persistent cough.
- Unaccustomed indigestion, constipation or diarrhoea.
- Abdominal pain and pain or difficulty in urinating.
- A lump, where the cancer is near the surface.
(c) (i) Carrying capacity is the maximum population that a given environment can support for an indefinite period or on a sustainable basis.
(ii) An implant is a tissue or organ inserted surgically into the human body to replace a defective one.
(iii) Carcinomas are tumours made-up of mainly epithelial cells that cover or line the body organs e.g., breast cancer.