I would use "are" in this case, but it wouldn't seem too weird to use "is". "Are" is the better choice because "dynamics" is plural. (In that last sentence, I was referring to "dynamics" as a word, so it's singular there.)

I would use "are" in this case, but it wouldn't seem too weird to use "is". It depends on the scenario: If you're talking about population dynamics in general, then you would use "is". If you're talking about a specific case with multiple different dynamics in it, then you would use "are".