This document provides an overview of protozoa by discussing their characteristics, types of reproduction, symbiotic relationships, taxonomy, and key examples. It notes that protozoa are unicellular, often rely on other organisms, and reproduce asexually through binary fission or budding and sexually. Symbiosis can involve parasitism, commensalism, or mutualism. The document then describes the major protozoan phyla - Sarcomastigophora, Apicomplexa, and Ciliophora - and examples within each, focusing on locomotion, structure, life cycles, and genetic control and reproduction.