alge

Algae

Definition of Algae: primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves

Algae are a large group of living things, at one time thought to be a type of plant. They have many of the characteristics of plants. They have chlorophyll and make their own food. However, they do not have roots, stems, leaves or flowers and are found mostly in all kinds of watery places worldwide. The study of algae is called phycology. Algae are major suppliers of food and oxygen within water communities. They are important in help provide petroleum. Certain algae are also eaten by humans as well.  The simplest forms of algae reproduce by simple cell division. Others reproduce by spores, fragmentation or reproduce sexually. Many algae get their names by the pigments or cells that color them such as blue-green algae, brown or red seaweed, etc. The most complex algae of both the red and green versions, are called seaweeds, and can be found washed up on beaches around the world. 
Algae may be similar to protozoa, that is, microscopic mobile organisms, differentiated by their ability to photosynthesize. 

Biofuels, as fuels made from biomass like plants, are known have a number of advantages and became a topic of interest in the late 20th century as many nations turned to alternatives to fossil fuel. Petroleum companies, as well as independent organizations, both invest in algae biofuel research and production, and algae-based fuels are commercially available in some regions.

Most of the simpler algae are unicellular flagellates or amoeboid, but colonial and non-motile forms 
have developed independently among several of the groups.
 references
http://en.wikipedia.org/