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

Population is an important level of organization in ecology and the unit of microevolution.
What is an important level of organization in ecology and the unit of microevolution?

Photoautotrophs and chemoautotrophs are two basic types of autotrophs.
Photoautotrophs and chemoautotrophs are two basic types of what?

Downregulation helps cells reduce their reaction to excessive hormone levels.
What helps cells reduce their reaction to excessive hormone levels?