Which phylum includes protozoa that primarily use pseudopodia for movement?

The phylum that includes protozoa primarily using pseudopodia for movement is Sarcodina. Members of this group, often known as amoeboids, are characterized by their ability to extend portions of their cytoplasm to form pseudopodia, which they utilize for locomotion and capturing food.

Pseudopodia are temporary, foot-like extensions of the cell, and they play a crucial role in the ameboid movement. This type of movement allows these protozoa to navigate through their environments, often in aquatic habitats, and facilitates processes like phagocytosis, where they engulf food particles.

In contrast, the other phyla listed do not primarily utilize pseudopodia. For instance, Mastigophora includes flagellates that move using whip-like flagella, while Ciliophora contains organisms that propel themselves with hair-like structures called cilia. Opalinida consists of protozoa that are primarily associated with the intestines of amphibians and have unique feeding and locomotion adaptations that do not involve pseudopodia. Understanding these distinctions highlights why Sarcodina is correctly identified as the phylum associated with movement via pseudopodia.