Final answer:
Young sand dollars use their tube feet to anchor themselves to the seabed, preventing them from being carried away by currents due to their light weight.
Step-by-step explanation:
Young sand dollars deal with being too light by utilizing their tube feet. While sea urchins and sand dollars do not have arms, they possess five rows of tube feet, which are essential for their mobility and interaction with their environment. These tube feet not only aid in slow movement but can also be used to anchor themselves in place. When young sand dollars feel that they are too light and at risk of being carried away by water currents, they can extend their tube feet to latch onto the sea bed or any available substrate to secure themselves.
These adaptations are crucial for the sand dollars' survival, as being too light could expose them to many dangers in the ocean, similar to how the loggerhead sea turtle hatchlings face various threats immediately after emerging on the beach. The ability to stay grounded despite their light weight is an important defense mechanism against being swept away and becoming easy prey for predators.