Protista

Though protists may be the among the smallest group of organisms on the planet, their importance to the environment is certainly not small. Algae, particular green algae, have a photosynthetic process very similar to plants. A healthy level of green algae in a lake or pond will provide much of the oxygen for the various animals in the body of water. Also, the algae are a food source for many of the small animals that live in the water. Some research has suggested that another type of algae, called diatoms, may produce most of the oxygen in our atmosphere.

Protozoans, which are animal-like protists, also have a major impact on the environment. Many of these microorganisms, such as Amoeba, form the ‘predator’ stratum of the food chain. Also, many protozoans are parasitic on humans and our livestock. Diseases like malaria and African sleeping sickness are caused by some of the smallest eukaryotic organisms on Earth.