Lichens are called pioneer colonisers of bare rock. How can they help in formation of soil?

Draw a graph for a wave representing wave disturbance and time for a sound changing from low pitch to high pitch, keeping the amplitude of the sound same.

Why lichens do not occur in Delhi whereas they commonly grow in Manali or Darjeeling?

What is a GM crop? Name any one such crop which is grown in India.

If there is low rainfall in a village throughout the year what measures will you suggest to the farmers for better cropping?