Chlorophyll a is so predominant in the environment that it is one of the principal reflective pigments used in remote sensing to map primary productivity. In addition there are a variety of accessory pigments that facilitate the process of photosynthesis such as phycobilins, phycocyanin and phycoerythrin , and others that serve as masking pigments such as carotenes and xanthophylls. The evolution of oxygen occurs in all the photosynthetic processes in algae, whereas the storage products differ from one group to another. There are some species of algae that are facultative heterotrophs, colorless and heterotrophic, parasitic, and phagotrophic. Morphological Diversity Morphological diversity is very high among the algae.
Many species are unicelluar, with a single cell serving as the plant.
Others are colonial, having many cells that are retained in a gelatinous matrix or are attached by cellular connections. A third general morphological pattern is that of a filament. In the latter, cells are attached by endwalls and form a thread. Some filamentous plants are uniseriate, without branches, while others are branched. There are parenchymatous algae, those whose cells are associated in nonbranching but closely associated cells.