What happens when a species from one ecosystem enters in new ecosystem in which it has no predators?

Answer overpopulation, depletion of resources, decline in numbers of lesser native animals in competition for same food source. If carnivorous they may eliminate other native animals as food for their ever growing numbers.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.