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

Ex Input:
What is the term for a symbiotic relationship in which one species benefits while the other species is not affected?

Ex Output:
commensalism

Ex Input:
What are the two types of vascular tissues found in vascular plants?

Ex Output:
xylem and phloem

Ex Input:
What is a random change in an organism's genes?

Ex Output:
mutation