13. Diatoms are microscopic phytoplankton with silica walls called frustules.
14. Fucoxanthin colors brown algae, which are large, multicellular seaweeds. The golden algae, which may be related to the brown algae, are photosynthetic but can eat other microorganisms when light or nutrient supplies decline.
21.5 The Red Algae Contain Unique Photosynthetic Pigments
15. Like plants, red algae have cellulose cell walls and chlorophyll a. Red algae produce phycobilin pigments that expand their photosynthetic range.
16. Red algae provide products such as agar and carageenan.
21.6 The Green Algae
17. Green algae are aquatic, store carbohydrates as starch, are photosynthetic and use the same pigments as plants. Many have alternation of generations. Unlike plants, green algae lack true roots, stems, and leaves, and they have less specialized cells.