What are unicellular and multicellular organisms?

A multicellular organism has

Living things are both unicellular and multicellular. Name some unicellular and multicellular organisms.

Compare unicellular and multicellular organisms, with one example.

How are the modes of reproduction different in unicellular and multicellular organisms?

Assertion:Whittaker's did not inculde unicellular green algae in prostista. Rerson: Distinction between uncicellular and multicellular organisms is not possible in case of algae.