They both, I guess you could say, interact with each other. If we didn't have gravity, we wouldn't have air pressure.
Phenotype = Observable/Physical characteristics.
Simple because there would be a larger gene pool, more opportunity for variation than a small population which has less of a gene pool and therefore less opportunity for variation.
Answer:
With a cold comes inflammation of the structures around the vocal cords. With the inflammation comes swelling of those structures. Thicker vocal cords vibrate more slowly and give a lower pitch.
