\u00a0[5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i) Carbon dioxide is considered as an air pollutant. Because it mixses with oxygen present in air and forms carbon monoxide which is harmful to man, vegetation, animals or even buildings.
\n(ii) BCG vaccine is given against tuberculosis.
\nDPT vaccine is given against the diseases viz; Diptheria, Pertussis and Tetanus.
\n(iii) 1. Illiteracy
\n2. Desire for a male child.<\/p>\nQuestion 4:<\/strong>
\n(a) (i) Draw a neat and well-labelled diagram of the chloroplast.<\/strong>
\n(ii) List the events taking place in the photo-chemical phase of photo-synthesis.
\n(iii) If you are planning an experiment to shew the effect of light on photosynthesis:
\n(1) Will you select white light or green light ? Justify your answer.
\n(2) Why would you select a destarched plant ? \u00a0 [5]<\/strong><\/p>\n(b) (i) Explain the term reflex action.<\/strong>
\n(ii) Expand the following biological abbreviations:
\n(1) DNA (2) AIDS.
\n(iii) State whether the following actions are \u2018voluntary action, simple reflex or conditioned reflex\u2019:
\n(1) Blinking
\n(2) Cleaning the table
\n(3) Playing on the keyboard
\n(4) Salivating when food is put in the mouth. \u00a0 [5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i)
\n
\n(ii) Following events take place in the photo-chemical phase of photo\u00acsynthesis :
\n(1) Activation of chlorophyll.
\n(2) Splitting of water (Photolysis).
\n
\n(3) The hydrogen ions are picked up by a compound NADP to form NADPH.
\n
\n(4) The oxygen component is given out as molecular oxygen.
\n2O ——>\u00a0O2<\/sub>
\n(5) The electrons are used in converting ADP into energy rich compound ATP by adding one phosphate group P2<\/sub>.
\n
\n(iii) (1) We will select white light because it will absorb green light and reflects other colours.
\n(2) We will select a destarched plant because destarching ensures that any starch present after the experiment has been formed under experimental conditions.
\n(b) (i) Reflex Action: Reflex action is an automatic, quick and involuntary action in the body brought about by a stimulus.
\nReflexes are of two types : (1) Simple (natural) reflexes and (2) Conditioned (acquired) reflexes.
\n(ii) (1) DNA:<\/strong> Deoxyribose Nucleic Acid.
\n(2) AIDS:<\/strong> Acquired Immune Deficiency Syndrome.
\n(iii) (1) Blinking:<\/strong> Simple Reflex.
\n(2) Cleaning of table:<\/strong> Voluntary Action.
\n(3) Playing on Keyboard:<\/strong> Conditioned Reflex.
\n(4) Salivation when food is put in:<\/strong> Conditioned Reflex.<\/p>\nQuestion 5:<\/strong>
\n(a) Given below is a diagrammatic representation of a defect of the human eye :<\/strong>
\n(i) Identify-the defect.
\n(ii) Mention two reasons for the above defect.
\n(iii) State how the defect can be rectified.
\n(iv) Name the part of the eye responsible for maintaining the shape of the eyeball. \u00a0 \u00a0 [5]<\/strong><\/p>\n(b) Name the hormones which lead to the following conditions :<\/strong>
\n(i) Diabetes Mellitus Exophthalmic goitre.
\n(ii) Growth of beard in women
\n(iii) Myxedema
\n(iv) Gigantism \u00a0 \u00a0 \u00a0[5]<\/strong><\/p>\nAnswer: (a)<\/strong> (i) \u201cHypermetropia\u201d because the image is formed behind the retina.
\n(ii) Two reasons:
\n1. Shortening of the eyeball from front to back.
\n2. The lens is too flat.
\n(iii) The defect can be rectified by the use of convex (converging) lens.
\n(iii) Ciliary muscles control\/maintain the shape of the eye ball.<\/p>\n(b)<\/strong> (i) Insulin.
\n(ii) Sex corticoids.
\n(iii) Thyroxin.
\n(iv) Somatotropin.
\n(v) Thyroxin.<\/p>\nQuestion 6:<\/strong>
\n (a) Study the diagram given below and then answer the questions that follow :<\/strong>
\n(i) Name the parts labelled 1 and 2. State the function of each part.
\n(ii) State any one function of the amniotic fluid.
\n(iii) What’ is the role of the umbilical cord in the development of the foetus ?
\n(iv) Name the part in the diagram which is endocrine in nature. \u00a0 \u00a0 [5]<\/strong><\/p>\n(b) (i) State Mendel\u2019s law of Independent Assortment.<\/strong>
\n(ii) A homozygous Tall plant (T) bearing red coloured (R) flowers Amniotic Fluid is crossed with a homozygous Dwarf plant (t) bearing white flowers (r):
\n(1) Give the Genotype and Phenotype of the F1<\/sub> generation.
\n(2) Give the possible combinations of the gametes that can be obtained from the F1<\/sub> hybrid.
\n(3) Give the dihybrid ratio and the phenotype of the offsprings of the F2<\/sub> generation when two plants of the F1<\/sub> generation above are crossed. \u00a0 [5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i) Part labelled 1: Placenta: It helps in the nutrition, excretion and respiration of the embryo.
\nPart labelled 2: Chorion: It forms the placenta.
\n(ii) Amniotic fluid acts as a cushion for the embryo and protect it from jerks or mechanical shocks.
\n(iii) Umbilical cord contains blood vessels and connects the placenta with the foetus. It means it helps in providing nutrition to the embryo and O2<\/sub> to foetus and removes CO2<\/sub> and excretory wastes from foetus blood to maternal blood.
\n(iv) Endocrine part of this diagram is \u2018placenta’.<\/p>\n(b)<\/strong> (i) Mendel\u2019s law of Independent Assortment: When there are two pairs of contrasting characters, the distribution of the members of one pair into the gametes is independent of the distribution of the other pair.
\n(ii) (1) Genotype of the F1<\/sub> generation – TtRr,
\nPhenotype of the F1<\/sub> generation – Tall plant and Red flower.
\n(2) Possible combination of the gametes from F1<\/sub> hybrid: TR, Tr, tR, tr.
\n(3) Dihybrid ratio and phenotype of the F2<\/sub> generation:
\n
\nQuestion 7:<\/strong>
\n (a) The diagram given below represents a stage during mitotic cell divisions in an animal cell:<\/strong>
\n(i) Identify the stage. Give a reason to support your answer.
\n(ii) Name the parts labelled 1, 2 and 3.
\n(iii) What is the chromosome number of the cell ?
\n(iv) Draw a neat, labelled diagram of the cell as it would appear in the next stage. Name the stage. \u00a0 [5]<\/strong><\/p>\n(b) Give reasons for the following:<\/strong>
\n(i) Plants begin to die when excess of soluble fertilizers are added to the soil.
\n(ii) Injury to the medulla oblongata results in death.
\n(iii) Gametes have a haploid number of chromosomes.
\n(iv) Green leaves are thin and broad.
\n(v) Lysosomes are termed suicidal bags of a cell. \u00a0 \u00a0 \u00a0[5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i) This diagram represents \u2018anaphase\u2019 of the mitosis division. In this centromere is divided separating sister chromatids of each chromosome. They are now drawn apart towards opposite poles.
\n(ii) Parts labelled 1 \u2014> aster rays.
\nParts labelled 2 \u2014> spindle fibres.
\nParts labelled 3 \u2014> chromatids.
\n(iii) 4 Chromosomes. Just double of the parent cell.
\n(iv) Stage: Telophase.
\n
\n(b)<\/strong> (i) Because of plasmolysis of plant cells due to hypertonic solutions of fertilizers.
\n(ii) Because due to injury in medulla oblongata, the projecting process of the axis vertebra in the neck pierces it. As a result the involuntary actions such as breathing and heart beat are stopped.
\n(iii) Because gametes undergo meiosis (reduction) cell division in which the number of chromosomes becomes half.
\n(iv) Green leaves are thin and broad so that more surface area is exposed to sunlight for photosynthesis.<\/p>\n