The word algae represent a large group of different organisms from different phylogenetic groups, representing many taxonomic divisions. In general algae can be referred to as plant-like organisms that are usually photosynthetic and aquatic, but do not have true roots, stems, leaves, vascular tissue and have simple reproductive structures. They are distributed worldwide in the sea, in freshwater and in wastewater. Most are microscopic, but some are quite large, e.g. some marine seaweeds that can exceed 50 m in length.

The unicellular forms are known as microalgae where as the multicellular forms comprise macroalgae.

Chlorella spp

Microalgae comprise a vast group of photosynthetic, heterotrophic organisms which have an extraordinary potential for cultivation as energy crops. They can be cultivated under difficult agro-climatic conditions and are able to produce a wide range of commercially interesting byproducts such as fats, oils, sugars and functional bioactive compounds.

Ulva lacuta

Seaweed is a loose colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. For that reason they are currently excluded from being considered plants.

The algae have chlorophyll and can manufacture their own food through the process of photosynthesis. Almost all the algae are eukaryotes and conduct photosynthesis within membrane bound structure called chloroplasts. Cyanobacteria are organisms traditionally included among the algae, but they have a prokaryotic cell structure.

Algae are an extremely important species. For one, they produce more oxygen than all the plants in the world, put together! For another, they form an important food source for many animals such as little shrimps and huge whales. Thus, they are at the bottom of the food chain with many living things depending upon them.

With the recent research and interest into using algae for producing biodiesel, they have the potential to become even more important.

Please see the following pages to know more about the basics of algae:

• Classification of algae
• Properties of algae
• Where do algae grow?
• Algae growth cycle
• Composition of algae
• Uses of algae
• Algae Bioinformatics