Name two inorganic substances which are used by autotrophs to make food.

What is the scientific term for animals that are:
$(i)$ Only meat eaters?
(ii) Only plant eaters?
(iii) Both plant and meat eaters?

State the function of the following in the alimentary canal:
$(i)$ Liver $(ii)$ Gall bladder $(iii)$ Villi.

What are heterotrophs? Give one example of heterotrophs.

Write the balanced chemical equation that represents the process of photosynthesis.

Given below is the experimental set-up to establish that one of the atmospheric gases is essential for photosynthesis in plants. $(a)$ Name the atmospheric gas which is essential for photosynthesis. $(b)$ What is kept in the watch-glass in figure 'a' and why? $(c)$ Write the balanced chemical equation for the process of photosynthesis. $(d)$ When do the desert plants take up carbon dioxide and perform photosynthesis?