Closely related to diatoms and also a young group, but very different in appearance. Some attain great size- 180 feet and grow 2 feet per day. Next to the golden-brown diatoms, the green algae are the second largest group of algae. They are also the most diverse of the algae, with at least 7000 species. They are found mostly in fresh waters and on land.
Most species float in rivers, lakes, reservoirs, and creeks.
They can also live on rocks, soil, and tree bark. Large, thin sheets of sea lettuce often totally obscure the muddy bottom in sheltered bay and estuary habitats. The higher terrestrial plants arose from a green algal ancestor. Some are consumed as food by humans.