Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Exotic species are also called invasive species because they threaten other species.
Why are exotic species also called invasive species?

The bird ancestor that lived in trees developed wings, which is commonly associated with birds.
The bird ancestor that lived in trees developed what feature commonly associated with birds?

As the temperature of water decreases, the water molecules slow down.
As the temperature of water decreases what happens to the speed of the water molecules?