Flagellates are a group of single-celled organisms that belong to the kingdom Protista. They are characterized by their use of whip-like structures called flagella, which help them move through water. Flagellates can be found in various environments, including freshwater, saltwater, and soil, and they play important roles in ecosystems as both predators and prey. Some flagellates are free-living, while others are parasitic, causing diseases in humans and animals. Notable examples include Giardia, which can cause gastrointestinal illness, and Trypanosoma, responsible for sleeping sickness. Their diverse forms and functions make flagellates significant in both ecological and medical contexts.