In a transverse wave, vibrations are perpendicular to the direction of the wave motion. In a longitudinal wave, vibrations are parallel to the direction of the wave motion.
In the transverse wave, crest and trough are the parts of a wave. The crest is a part where the displacement is maximum. While the trough is the part where the displacement is minimum.
In the longitudinal wave, the compression and the rarefaction are the part of a wave. In compression, the particles are very close to each other. While, in rarefaction, the particles are far apart.
Kettlewell thought that if natural selection caused the change in the moth population, the following must be true: Heavily polluted forests will have mostly dark peppered moths. Clean forests will have mostly light peppered moths. Dark moths resting on light trees are more likely than light moths to be eaten by birds.
