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: What long molecules are composed of chains of units called monomers? Answer: polymers
Polymers are long molecules composed of chains of units called monomers.

Question: Differences in fitness among different members of a population can lead to what kind of selection? Answer: natural selection
Natural selection occurs when there are differences in fitness among members of a population.

Question: Conduction from the core has what effect on the lower mantle? Answer: it heats it
Conduction from the core heats the lower mantle.