Describe an experiment to show that water has maximum density at 4°C. What important consequences follow from this peculiar property of water? Discuss the importance of this phenomenon in nature.

Draw a diagram showing the temperature of various layers of water in an ice covered pond.

Plants use …………… of the total energy absorbed by them in photosynthesis for producing their food.

1. 40%
2. 50%
3. 5%
4. 0.02%

Food chain begins with :

1. respiration
2. photosynthesis
3. decomposition
4. decay