Definition
*Ulvales* is an order of green algae within the class Ulvophyceae. These algae are primarily marine, with a few freshwater representatives. They are characterized by their simple thallus structure, often forming flattened sheets or tubular filaments. *Ulvales* reproduce both sexually and asexually. They include familiar seaweeds like sea lettuce (*Ulva*). Think of them as a group of green algae with simple forms found mainly in the ocean. They exemplify the diversity of marine algae.