I believe that it's this 1st blank : monogamy. Reason: I believe that it's monogamy because it's when someone/something is has one mate. Also, monogamy is the one with the closest definition as stated is the question.
2nd blank : polygyny Reason: The answer to this one may be polygyny because it is when someone/something has more than one female mate (like in your question).
Hope this helps. Disclaimer:I'm not sure if it's right though :)
Scientists use fossils to learn about organisms' lives and evolutionary relationships, to understand geological change, and even to locate fossil fuel reserves.
