Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[EX Q]: Question: What occurs when two wave crests overlap? Answer: constructive interference
[EX A]: Constructive interference occurs when two wave crests overlap, doubling the wave amplitude at that location.

[EX Q]: Question: What type of cell layer do flatworms have? Answer: mesoderm
[EX A]: Flatworms have a mesoderm cell layer and simple organ systems. They also show cephalization and bilateral symmetry.

[EX Q]: Question: What term is used to describe cells without a nucleus? Answer: prokaryotic
[EX A]:
Prokaryotic cells are cells without a nucleus.