**3.3** *Rhodophyta*

They are primarily marine in distribution sometimes inhabiting the deep water, with less than 3% (150 species from 20 genera) of the over 6500–10,000 species occurring in truly freshwater habitats [25]. The red algae are characterized by eukaryotic cells, with the complete absence of flagellar structures, food reserves of starch, presence of phycobilins, chloroplasts without stacked thylakoids, and no external endoplasmic reticulum.
