Here's why:
* Apicomplexans are a large group of parasitic protozoa that have a characteristic apical complex, a structure at one end of the cell that helps them penetrate host cells. They lack structures like cilia or flagella for movement, and rely on the host's environment for transportation.
* Other protozoa that lack independent movement are also sometimes called sessile, but this term is more broadly used to describe any organism that doesn't move freely.
Important note: While apicomplexans are a large group, there are some protozoa within other groups that are also not capable of independent movement. The term "apicomplexan" is specific to this group.
