Bryozoa are small, aquatic invertebrates that typically form colonies made up of numerous individual animals called zooids. These colonies can vary in shape and size, often resembling moss or coral. Bryozoans are found in both marine and freshwater environments, and they play a role in the ecosystem by filtering water and providing habitat for other organisms. Each zooid has specialized functions, such as feeding, reproduction, or defense. Bryozoans reproduce both sexually and asexually, allowing them to thrive in various conditions. Their hard, calcareous structures contribute to the formation of sedimentary rocks, making them important in geological studies.