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

Example Input: If two populations do not mate and produce fertile offspring, separate species result.
Example Output: If two populations do not mate and produce fertile offspring, what results?

Example Input: Gravity makes soil and rock particles move gradually down the slope during each thaw.
Example Output: What makes soil and rock particles move gradually down the slope during each thaw?

Example Input: Each species has a particular way of making a living, which is called its niche.
Example Output:
Each species has a particular way of making a living which is called its what?