Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: living things all require energy conservation as a trait. 
Question: living things all require energy conservation as a what?
trait.

Fact: parasites can cause harmful diseases. 
Question: certain diseases can be caused by what?
parasites.

Fact: Evolution is a change in the genetic traits of living things over time. 
Question: Evolution is a change in the genetic traits of living things over what?

time.