Though all algae contain chlorophyll, the major divisions can for the most part be distinguished on the basis of their predominant apparent color, due to other photosynthetic pigments that mask the chlorophyll green.
The main branches/lines of algae are:
- Chromista- this line includes the Brown Algae golden brown algae, and diatoms. The plastids in these algae contain Chlorophylls A and C. ( see: Brief Introduction to the Phaeophyta, Brown Algae – from Wikipedia)
- The Red Line – this is an early branch of marine (algae Introduction to the Rhodophyta, Red Alga – from Wikipedia) containing just Chlorophyll A. Red Algae can often be seen coating wave washed rocks. A characteristic of red algae is that their plastids contain only one type of chlorophyll -- chlorophyll a. This is different from Green algae and plants which have both chlorophyll a and b.
- Dinoflagellates – these evolved on a separate line that includes, surprisingly, the ciliated protists. (see: Introduction to the Dinoflagellata from UMCP, Berkeley, Dinoflagellate Information – from MBARI, Dinoflagellate – from Wikipedia)
- The Euglenids – this independent line of single celled organisms that include both photosynthetic and non-photosynthetic species (see: Euglenid – from Wikipedia)
- The Green Line, is related to plants. Plants and green algae Introduction to Green Algae) have chlophylls A and B.
The three most prominent lines of algae are the Brown Algae (Chromista), the red algae, and the Green algae of which some of the most complex forms are founds among the green algae. This lineage (green algae) eventually led to the higher land plants. The point where these non-algal plants begin and algae stop is usually taken to be the presence of reproductive organs with protective cell layers, a characteristic not found in the other alga groups.