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Section B

Q. 17. A young green plant receives sunlight from one direction only. What will happen to its shoots and roots? 1

Ans. (1) The roots bend away from light.
(2) The stem bends towards the light.

Q. 18. Name the plant hormones which help/promote
(i) cell division (ii) growth of the stem 1

Ans. (i) Cytokinins help/promote cell devision.
(ii) Auxins help/promote growth of the stem.

Q. 19. Name any two forest products, each of which is the basis for some industry. 1

Ans. (i) Wood. It is used in timber industry, paper mills etc.
(ii) Latex of Rubber plant. It is used in various rubber industries like tyres etc.

Q. 20. What is nuclear energy? State its one advantage. 2

Ans. The energy released during a nuclear reaction is called nuclear energy. The energy released is mainly in the form of heat. Advantage of nuclear energy. A small amount of mass of nucleus is destroyed during a controlled nuclear reaction which gets converted into a tremendous amount of energy to produce electricity.

Q. 21. Name the information source of making proteins in the cell. State two basic events in reproduction. 2

Ans. The information source of making proteins in cell is DNA.

Two basic events in reproduction are:
(i) The creation of a DNA copy. Here the cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell.
(ii) DNA copying is accompanied by the creation of an additional cellular apparatus, and then the DNA copies separate, each with its own cellular apparatus. Effectively, a cell divides to give rise to two cells.

Q. 22. List four advantages of using solar cells. 2

Ans. Advantages of using solar cells:
(i) They have no moving parts.
(ii) They require almost no maintenance.
(iii) They work quite satisfactorily even without using any light focussing device.
(iv) They can be set up in remote, inaccessible and very sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive.

Science 2009 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Outside Delhi		Foreign
	Set 1 (PDF)		Set 1 (PDF)		Set 1		Set 1		Set 1 (PDF)
					Set 2		Set 2
					Set 3		Set 3