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 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.
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.
The plant-like Protists are called algae. The main characteristics of algae include that they are aquatic, they range in size from unicellular to multicellular and they 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 pigment(s) and (2) type of storage product(s).
The cell walls of desmids are made of cellulose. They contain various photosynthetic pigments, but their primary pigments are the chlorophylls. Some forms are symbionts, such as the algal component of the lichen. Plant starch is their storage product.
This organism has spiral chloroplasts. The chloroplasts contain enlarged starch storage areas called pyrenoids. Many desmids are made of two attached segments called semicells.