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Q. 25. The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species. Why? Justify your answer. 3

Ans. The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species because the process of reproduction can occur between them. These differences are known as variations, i.e. the occurrence of differences among the individuals of a species. Although all human beings look different, they have the same number of chromosomes. A large number of variations occur in sexual reproduction because two parents are involved in the process and result in the birth of human beings of different colour, size and looks.

Q. 26. What is meant by sustainable management? The environmentalists are  insisting upon sustainable natural resources management”. State its four advantages. 3

Ans. The development which meets the current basic human needs and also preserves the resources for the needs of future generations is called sustainable management.

A system of controlling the use of natural resources in such a way as to avoid their wastage and to use them in the most effective way is called sustainable management.

Advantages:
(i) The resources of the earth are limited. Proper management of these natural resources can ensure that these are used judiciously so that they fulfil the needs of the present generation and also last for the
generations to come.
(ii) The proper management of natural resources takes into consideration long-term perspective and prevents their exploitation to the hilt for short term gains.
(iii) Proper management can ensure equitable distribution of natural resources so that all the people can be benefitted.
(iv) Proper management will take into consideration the damage caused to the environment during the extraction or use of the natural resources and find ways and means to minimize the damage.

Q.27. (a) Draw a diagram to show the human alimentary canal and label on it the following :
Gall bladder, stomach Name the longest part of the alimentary canal.
(b) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds? 5

Ans. (a) Human alimentary canal. See Q.2, (L.A.T.), Chapter 6 (Only diagram). [Page 67
Longest part of the alimetary canal is small intestine (about 7 m long).
(b) Such separation of oxygenated and deoxygenated blood is necessary for highly efficient supply of oxygen to the body of birds and mammals which have high energy needs and constantly need energy
to maintain their body temperature.

Or

(a) Draw a diagram to show excretory system in human beings and
label on it the following:
Aorta, Vena Cava
Name the excretory unit of kidney.

(b) Differentiate between aerobic respiration and anaerobic respiration. After vigorous exercise, athletes and players generally experience cramps in their leg muscles. Why? 5

Ans. (a) Excretory System in human beings. See Q.27, (S.A.T.), Chapter 6 (Only diagram). [Page 65
Nephron is the excretory unit of kidney.

(b) Difference between aerobic respiration and anaerobic respiration. See Q. 16 (S.A.T.), Chapter 6. [Page 62-63 After vigorous exercise, athletes and players generally experience cramps in their leg muscles because anaerobic respiration takes place in the muscles during vigorous physical exercise. Oxygen gets used up faster in the muscle cells than that can be supplied by the blood. Anaerobic respiration produces lactic acid with release of a small amount of energy. The sudden build up of lactic acid in the muscles causes muscular cramps.

Science 2009 Question Papers Class X
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