Originally, there were two subsections in the Protist (a/k/a Protoctista) kingdom: the Phylum Protozoa (the animal-like protists) and the Division Algae (the plant-like protists). Both groups were previously members of the animal and plant kingdoms, respectively. When you study zoology and botany, these groups will be included in the review of the animal and plant kingdoms. Since the early days of the Protist kingdom in the 1800’s a few more groups have been added to the kingdom, including the Fungus-like (slime molds and water molds) Protists.
The Protist kingdom originally included only unicellular and colonial life forms, but a limited number of multicellular forms are now included (primarily green algae).
The Protozoa ("first animals") are the animal-like (heterotrophic, motile) Protists and are classified (in part) based upon their method of motility (such as cilia, pseudopods, and flagella). Representatives of this group are primarily unicellular or colonial.
The algae are aquatic, range in size from unicellular to multicellular and are photosynthetic. These organisms account for at least half of all photosynthetic organisms on Earth. One of the reasons they are not considered true plants is because they lack a waxy cuticle. Another reason is that the algae have chlorophyll-A like the true plants, but differ in terms of other pigments. These organisms are ecologically important not just because of photosynthesis, but also because they are used either as food or in the preparation of some forms of food. The basis of their classification includes (1) type of pigments and (2) type of storage products.
The Fungus-like Protists are saprophytes (saprobes), which means they are heterotrophs but they absorb instead of actively seeking their food. They have a body design similar to the members of the Fungus Kingdom.
Use pages 18-23 and 32-38 in the Photo Atlas as a reference for your review of the Protists. Recall that the authors of your Photo Atlas do not use the same exact method of classification as the authors of your textbook. Hence, the water molds and most algae are placed in the Protist group by your text authors, but not the Photo Atlas authors.