Final answer:
The flagellate protozoan moves through liquid with at least one flagellum, and this stage is known as flagellate. Flagella, made of microtubules, can pull or push the organism, contributing to its movement and response to stimuli.
Step-by-step explanation:
The flagellate protozoan uses flagella for movement through liquid, and this stage is known as a flagellate.
Many protists exhibit different forms of locomotion, such as flagella, cilia, or pseudopodia. In flagellate protozoans, the flagella function somewhat like a propeller, either pulling or pushing the organism forward in its liquid environment. The flagella are composed of microtubules and can vary in number from one to several, depending on the organism. Opisthokonts, such as the choanoflagellates, uniquely have a single posterior flagellum which pushes the cell.
Other protozoa may have anterior flagella that pull them along. Protozoan motility is not just for navigation but can also be a response to stimuli, a behavior termed taxis. Additionally, protozoa can be either free-living or parasitic, playing important roles in ecosystems and sometimes in disease transmission.