instruction:
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.
question:
Question: Plant cells have structures that animal cells? Answer: lack
answer:
Plant cells have structures that animal cells lack. What important process takes place in plant cells but not in animal cells that might explain their differences?.

question:
Question: What type of cell layer do flatworms have? Answer: mesoderm
answer:
Flatworms have a mesoderm cell layer and simple organ systems. They also show cephalization and bilateral symmetry.

question:
Question: What is defined as a push or pull acting on an object? Answer: force
answer:
Force is defined as a push or pull acting on an object. Forces include gravity, friction, and applied force.