Simplify the following text for a Grade 13 native English-speaking person.
Original: Algae ( or ; singular alga , Latin for `` seaweed '' ) are a large and diverse group of simple , typically autotrophic organisms , ranging from unicellular to multicellular forms , such as the giant kelps that grow to 65 meters in length .
Simplified: Algae are a large and diverse group of simple , typically autotrophic organisms , ranging from unicellular to multicellular forms .