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Advantages:
(i) Water from a dam is used for irrigation in fields through a network of canals. Dams ensure round the year water supply to the crop fields and help raise agricultural production.
(ii) The water rushing down the dam turns turbines which run electric generators to generate electricity.

Ill-effects:
(i) Social problems because they displace large number of peasants and tribals without adequate compensation or rehabilitation.
(ii) Economic problems because they swallow up huge amounts of public money without the generation of proportionate benefits.

Q. 26. What is meant by exploitation of resources with short term aims? List its four advantages. 3

Ans. Exploitation of resources with short term aims means that management of natural resources is done in such a way so as to achieve short term gains which are enjoyed by just a handful of rich and powerful people. Resources are exploited to the hilt to meet the needs of the present generation without thinking of the needs of future generations.
Advantages:
(1) The main advantage of exploiting resources with short-term perspective is to get huge profit without any accountability.
(2) These resources fulfil the needs of present generation.
(3) Man gets a variety of raw materials from natural resources which are indispensable for the growth and development of our present day industries.
(4) It increases the (present day) growth rate of economy.

Q. 27. (a) What is meant by breathing? What happens to the rate of breathing during vigorous exercise and why?
(b) Define translocation with respect to transport in plants. Why is it essential for plants? Where in plants are the following synthesised:
(i) Sugar (ii) Hormone 5

Ans. (a) Breathing. The mechanism by which organisms obtain oxygen from the air and release carbon dioxide is called breathing.
During vigorous exercise the demand of oxygen in the body tissues increases exponentially. Due to this, the rate of breathing increases during vigorous exercise.
(b) Translocation. The transport of food from the leaves to other parts of the plant is called translocation.
Leaves make food by the process of photosynthesis. The food made by leaves is in the form of simple sugar (glucose). Other type of substances called plant hormones are made in the tips of roots and
shoots. Every part of the plant needs food. So, food made in the leaves of a plant has to be transported (or carried) to all the different parts of the plant like branches, stem and roots etc.
(i) Sugar is synthesized in the leaves.
(ii) Hormones are synthesized in the tips of growing roots and shoots.

Or

Draw sectional view of the human heart and label on it the following chambers:
(i) Left atrium (ii) Right atrium (iii) Left ventricle (iv) Right ventricle State one function of each chamber in a tabular form. 5

Ans. Diagram. See Q.27, Sample Paper II. [Page 19
Also add : (iv) Right ventricle—Send deoxygenated Blood to the lungs.

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