The endoskeletons and exoskeletons of various animals are also formed from:

What are the three ways by which $CO_{2}$ is returned back into the atmosphere?

What are the two ways in which carbon dioxide is fixed in the environment?

How can soil be conserved?

Why does the Mathura refinery pose problems to the Taj Mahal?

$(a)$ How do forests influence the following?
$(i)$ Air
$(ii)$ Soil
$(iii)$ Water
$(b)$ Is the atmosphere on Venus and Mars different from our atmosphere? How?