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

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

Water affects the availability of oxygen important element in aquatic environments and in flooded soils.
Water affects the availability of what important element in aquatic environments and in flooded soils?

Selective breeding involves choosing certain organisms to reproduce with one another in order to pass on specific, desirable traits to their offspring.

Which process involves choosing certain organisms to reproduce with one another in order to pass on specific, desirable traits to their offspring?