CBSE Guess > Papers > Question Papers > Class X > 2009 > Science > Science

Q. 23. Name the male and female gametes in animals. What is fertilization and where does it take place in human females? 2

Ans. In animals male gamete is called ‘sperm’ and the female gamete is called ‘ovum’ (or ‘ova’).

Fertilization. The fusion of a male gamete with a female gamete to form a zygote during sexual reproduction is called fertilization. The fertilization of the ovum (or egg) takes place in the oviduct.

Q. 24. How is ozone formed in the upper atmosphere? Why is the damage of ozone layer a cause of concern to us? State a cause of this damage. 2

Ans. Ozone is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas by the following process:
Step 1. The high energy UV radiation running from the sun splits oxygen gas into free oxygen atoms

Step 2. The free oxygen atoms thus produced are very reactive. One oxygen atom reacts with an oxygen molecule to form an ozone molecule.

This layer of ozone prevents the entry of harmful UV radiation to the earth’s surface, hence the damage to ozone layer is a cause of great concern to the mankind.

Chlorofluorocarbons (CFCs), which are used in refrigerants, deodrandts and in fire extinguishers, are one of the major causes of depletion of ozone layer.

Q. 25. What was “Chipko Movement”? How did this movement ultimately benefit the local population and the environment? 3

Ans. ‘Chipko Movement’: Chipko Movement is an example of contribution of common people towards the conservation of forests. The Chipko Movement [also called Hug the tree movement] originated from an incident in a remote village called ‘Reni’ in Garhwal (Himalayas), where the people of this village clasped the tree trunks with their arms to protect them from being cut down by a contractor’s workers. The people acted this way because they knew that this mass deforestation would spoil their healthy environment. The forest trees were thus saved. The Chipko Movement quickly spread across all the communities and hence helped in the conservation of forests and thus helped in safeguarding the environment

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)
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