The three organisms that belong in the same phylum as your Protist are:1. Algae: Algae are plant-like Protist and are all photosynthetic Protists. 2. Protozoa: Protozoa are animal-like Protists3. Heterotrophs: Heterotrophs are fungi-like Protists. An example is what is known as True Slime Moulds.
A Protist is any organism that is not a plant, animal or fungus. They are normally unicellular, although some can be multicellular, for example, Algae. They all have a nucleus and they mostly live in water.