Given a scientific question, generate a correct answer to it.

Example Input: Lampreys use their sucker to feed on what part of other fish species?
Example Output: blood

Example Input: The regions of a material where the north and south poles of atoms are aligned are called what?
Example Output: magnetic domains

Example Input: What phenomenon is essential in order for evolution to occur because it increases genetic variation and the potential for individuals to differ?
Example Output:
mutation