Which stage is not part of gradual metamorphosis?

The correct answer identifies the pupa stage as not part of gradual metamorphosis, which is a distinct life cycle process observed primarily in insects such as grasshoppers and cockroaches. Gradual metamorphosis consists of three main stages: egg, nymph, and adult. In this process, the organism hatches from the egg into a nymph, which resembles a smaller version of the adult but without fully developed wings or reproductive organs. The nymph grows and molts several times until it reaches maturity as an adult.

Pupa, on the other hand, is a stage associated with complete metamorphosis, which involves four distinct stages: egg, larva, pupa, and adult. During the pupal stage, the insect undergoes significant transformation, which is not part of gradual metamorphosis. This difference in stages is crucial for understanding the various developmental pathways in the insect world.