Final answer:
The first zooid to settle in a new area at the end of planktonic life is called a larva.
Step-by-step explanation:
The first zooid to settle in a new area at the end of planktonic life is called a larva. Larvae are the early life stages of many aquatic organisms, including crustaceans like barnacles and crabs. They typically start as free-swimming organisms, but eventually attach to a substrate and transform into a sessile form.