It is a eukaryote with a cell membrane and cell wall containing chlorophyll a, b, carotenoids, and others as well. There are two equal flagella. The cell wall is made up of cellulose fibres and pectin. Carbohydrates are stored by starch that turns black when stained with Lugol's. They will grow in encrusted colonies, filamentous branching, and plant like thalli. Asexual and sexual reproduction occur, often with alternation of generations. There is a diverse range of habitats. They have widespread ecological roles and critical habitat that supports fishing.