Why do iridescent colors seen in some seashells (such as abalone shells) change as the shells are viewed from various positions?

iridescent colors seen in some seashells change as the shells are viewed from various positions because the color shown depends on where your light source is coming from. The color changes as you tilt the shell in different positions, changing where the light source is hitting it.

as in mitosis, dna replication occurs during interphase.   in meiosis, it occurs specifically in s phase of interphase 1.

the endomembrane system i think