The Protista Kingdom consists of unicellular lifeforms (lifeforms with only one cell) who have a nucleus. The primary difference between protists and monera is that protists are more complex, having a nucleus.
Many protists appear to be both plant and animal. Like plants, they are green, and can create their own food. However, like animals, they have moving body parts and are able to move around their environments. You can see why scientists no longer classify living things into two kingdoms.Into which would you put these unique organisms?
Biologists believe that ancient protists were the ancestors of plants and animals.