When using terms such as coelomates and pseudocoelomates, a “grade” is

In this case, a grade refers to a group whose members share major or key biological characteristics.

This is what i found on google “phytoplankton, tiny organisms that live in the ocean, are autotrophs. some types of bacteria are autotrophs. most autotrophs use a process called photosynthesis to make their food.” i hope this you for what your looking for