Aspecies brought to an area through human activities is known as what

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it