nephrons<\/a> are highly coiled in this region.
\n(iii) Wooden frames of doors and windows get jammed due to process of imbibition. In this process, water is adsorbed or absorbed by surface attraction. Wood have a strong affinity for water (hydrophillic). Thus, they absorb or imbibe water or moisture from their surroundings and swell up.
\n(iv) The anterior wall of middle ear contains an opening that leads directly into Eustachian tube. This tube connects the middle ear to throat. Hence the passage for infection is common and it may lead to ear infection.
\n(v) It occurs due to conditioned reflexes. These reflexes are learned responses to stimuli acquired individually during the life of an organism.<\/p>\nQuestion 6:<\/strong>
\n (a) The figure given below shows the epidermal cells of an onion bulb. This cell was then transferred to a drop of sugar solution.<\/strong>
\n(i) Draw a well labelled diagram of the epidermal cell as it would appear after immersion in a strong sugar solution.
\n(ii) What scientific term is used for the changes as shown in (i) above ?
\n(iii) What should be done to restore the cell back to its original condition ?
\n(iv) Give the scientific term for the recovery of the cell as a result of the step taken in (iii) above.
\n(v) Define the term osmosis. \u00a0[5]<\/strong><\/p>\n(b) Briefly explain the following terms :<\/strong>
\n(i) Genes.
\n(ii) Cytokinesis in plant cells.
\n(iii) Guttation.
\n(iv) Diabetes insipidus.
\n(v) Disinfectants. \u00a0 \u00a0 \u00a0 \u00a0[5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i)
\n
\n(ii) Plasmolysis<\/strong> is technical term used for the above change.
\n(iii) To restore the cell back to its original condition, it must be placed in hypotonic solution immediately after it gets plasmolysed.
\n(iv) Deplasmolysis<\/strong> is technical term used for recovery of the cell as a result of the step taken in (iii) above.
\n(v) Osmosis:<\/strong> It is the movement of water molecules from the region of its lower concentration to the region of higher concentration through semipermeable membrane.<\/p>\n(b)<\/strong> (i) Genes:<\/strong> Genes are units of heredity that determine particular traits (e.g., colour of hair, blood group, colour of eye etc.)
\n(ii) Cytokinesis in plant cells:<\/strong> Cells in multicellular plants do not have centrioles. The division of cytoplasm occurs by the formation of a new cell wall in the equatorial regien at the end of anaphase. In telophase, new cellulose particles are gradually deposited in the equatorial zone. The particles extend on either side, from the centre towards the periphery (centrifugal) until it completely divides the cell. These particles fuse together to form a delicate plate membrane.
\n(iii) Guttation:<\/strong> The loss of water in the form of water droplets along the margins of leaves through hydathodes.
\nIt takes place due to increased hydrostatic pressure that builds up within the cells. The wall pressure that develops in fully turgid parenchymatous cells force the water out.
\n(iv) Diapedes insipidus:<\/strong> The condition occurs due to lesser secretion of vasopressin (Anti-diuretic hormone) from the posterior lobe of pituitary gland. The disease is characterized by excretion of large amounts of urine and subsequent dehydration and thirst. No sugar or albumin is present in the urine. A person with severe diabetes insipidus may die due to dehydration if deprived of water for few days.
\n(v) Disinfectants:<\/strong> These are powerful chemical substances used for destroy\u00acing microbes in spots, places for sterilizing operation theatres and surgical instruments. They are not applied on the body due to their strong corrosive nature eg. Cresol, Phenol, Lysol, DDT etc.<\/p>\nQuestion 7:<\/strong>
\n(a)<\/strong> (i) Draw a well labelled diagram to show the anaphase stage of mitosis in a plant cell having four chromosomes.<\/strong>
\n(ii) State any two harmful effects of acid rain.
\n(iii) Expand the following biological abbreviations :
\n(1) NADP (2) ACT \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0[5]<\/strong><\/p>\n(b)<\/strong> (i) List any two major activities of the Red Cross.<\/strong>
\n(ii) Write any two major reasons for the population explosion in the world.
\n(iii) Write the names of four nitrogenous bases in a DNA molecule. \u00a0[5]<\/strong><\/p>\nAnswer:<\/strong>
\n(a)<\/strong> (i)
\n
\n(ii) Harmful effects of acid rain:<\/strong> It has following effects :
\n(a) Acid rain corrodes buildings and metal structures.
\n(b) Acid rains also makes soil acidic which becomes unsuitable for cultivation. It also causes damage to plants.
\n(iii) (1) NADP:<\/strong> Nicotinamide Adenine Dinucleotide Phosphate (2) ACT:<\/strong> Adrenocorticotropin.<\/p>\n(b)<\/strong> (i) Activities of Red Gross:<\/strong> These are as follows :
\n(a) It aims at providing social and medical care during war, and natural calamities such as famine^ drought, flood, earthquake etc.
\n(b) To arrange for ambulance during emergencies and lookafter maternal and child welfare centres.
\n(ii) Reasons for population explosion in the world:<\/strong> The reasons are as follows :
\n(a) Better health care at all age groups and fewer deaths due to better medical aids.
\n(b) Large scale immunization against communicable diseases.
\n(c) Balanced and improved nutrition specially for growing children.
\n(d) More children reach the reproductive age.
\n(iii) Nitrogenous bases of DNA molecules are:<\/strong>
\n<\/p>\n