Final answer:
Krill is the small crustacean that is vital to most Antarctic life forms, serving as a primary food source for many animals.
Step-by-step explanation:
According to National Geographic, the small crustacean that is essential to the survival of most Antarctic life forms is krill. Krill are a type of crustacean that serve as a major food source for many Antarctic animals, including whales, penguins, and seals. Without krill, these animals would struggle to find enough food to survive.