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

Ex Input:
Metabolism produces waste energy in the form of heat, which helps warm-blooded (endotherm) animals conserve and maintain heat at a relatively constant body temperature.

Ex Output:
Metabolism produces waste energy in the form of heat, which helps what type of animal conserve and maintain heat at a relatively constant body temperature?

Ex Input:
The bird ancestor that lived in trees developed wings, which is commonly associated with birds.

Ex Output:
The bird ancestor that lived in trees developed what feature commonly associated with birds?

Ex Input:
A skeleton that consists of hard, mineralized structures located within the soft tissue of organisms is called endoskeleton.

Ex Output:
A skeleton that consists of hard, mineralized structures located within the soft tissue of organisms is called what?