Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Tornadoes can occur in any.
At what time of the year can tornadoes occur?

Virtually all aquatic organisms depend directly or indirectly on protists for food.
Virtually all aquatic organisms depend directly or indirectly on what for food?

Water makes up most of biological tissues.
What makes up most of biological tissues?