----------------------------------------------------------------Algae

The algae comprise several different groups of organisms that produce energy through photosynthesis. However, most are not classified within the Kingdom Plantae but in the Kingdom Protista. Most conspicuous are the seaweeds, multicellular algae that may roughly resemble terrestrial plants, but are classified among the green, red, and brown algae. These and other algal groups also include various single-celled organisms. The embryophytes developed from green algae (Chlorophyta); the two groups are collectively referred to as the green plants or Viridiplantae. The Kingdom Plantae is often taken to mean this monophyletic grouping. With a few exceptions among the green algae, all such forms have cell walls containing cellulose and chloroplasts containing chlorophylls a and b, and store food in the form of starch. They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae.
The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. The same is true of the red algae, and the two groups are generally believed to have a common origin (see Archaeplastida). In contrast, most other algae have chloroplasts with three or four membranes. They are not close relatives of the green plants, presumably in origin acquiring chloroplasts separately from ingested or symbiotic green and red algae

Algae
Algae are photosynthetic. Ecologically, they are very important as half of all the photosynthetic production of organic matter can be attributed to them. They all use chlorophyll a, but each individual kind uses other pigments. In fact, they are named for their color.

Euglenophyta Euglena Green (a, b, carotenoids, xanthophylls)
Dinoflagellata Dinoflagellates Brown (a, c, carotenoids, xanthophylls)
Bacillariophyta Diatoms Olive brown (a, c, carotenoids, xanthophylls)
Chrysophyta Golden algae Golden olive (a, often c, carotenoids, xanthophylls)
Phaeophyta Brown algae Olive brown (a, c, carotenoids, xanthophylls)
Rhodophyta Red algae Red to black (a, caortenoids, phycobilins, some d)
Chlorophyta Green algae Green (a, b, carotenoids)