An organism is considered a kind of algae if it is aquatic and is autotrophic.(3) Algae is plant like as it uses sunlight to get energy through photosynthesis. Algae ranges in size from unicellular and microscopic species(microalgae) to some species that can be more than 50m long(macroalgae). There is a huge variety in the species and types of algae. There are about 37,000 species of true algae and 4,000 species of cyanobacteria, and more species are being discovered all the time. Algae can be found most places as long as there is access to sunlight (for energy) and water. Some types of algae live near places such as hot springs or lava flows; there kinds of algae are called extremophiles.(1)
A well known kind of algae is seaweed. Seaweed is any macroscopic marine algae.(2) There are three types of seaweed: Rhodophyta (red), Phaeophyta (brown), and Chlorophyta (green). Kelp is actually a kind of brown seaweed. The most diverse type of seaweed is green algae. There are about 7,000 known species.(3)
Algae is very important as it is a big contributor to the food chain and makes up about 50-70% of the earth’s oxygen. Algae can also be used as fats, oils, and sugars in human products. Another very useful way algae can be used is as biofuel.(2)
Sources:
1. "What Are Algae?" Encyclopedia of Life. Accessed January 05, 2017. http://eol.org/info/526.
2. "Introduction to Algae & Basics, Types of Algae, Forms of Algal Strains - Oilgae - Oil from Algae." Introduction to Algae & Basics, Types of Algae, Forms of Algal Strains - Oilgae - Oil from Algae. Accessed January 05, 2017. http://www.oilgae.com/algae/algae.html.
3. "Introduction to the "Green Algae"" Introduction to the Green Algae. Accessed January 05, 2017. http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html.