The factor that will prevent the species from becoming an invasive one is predation.
If the species of fish introduced is an apex predator, there will be no organisms present to keep the population of the fish in check. Moreover, if the introduced species has a selective advantage over those that it shares the same niche with, then it is more likely to oust these species from the food chain by consuming all of their resources.
I think the correct stage would be In the prophase.
Are you referring to vocal cords?
The contractile vacuole expels water out of the cell by contrasting.
