The photic or euphotic zone extends to what depth from the upper surface of the sea?

In the oceans,the environment is perpetually dark at depths of:

Organisms that can tolerate and thrive in a wide range of temperatures are $P$,while those restricted to a narrow range of temperatures are $Q$. Choose the correct option for $P$ and $Q$.
$P \quad\quad Q$

Species that can tolerate a narrow range of temperature are called $.............$ .

In which form do organisms realize the emergence of their environment?

Plants grow sparsely in arid regions of the world.