Blastozoans

Blastozoans are a group of animals that are characterized by their simple, radially symmetrical bodies and the presence of a blastopore, a small opening in the embryo that becomes the mouth. This group includes several phyla, the most well-known of which is the phylum Cnidaria, which includes jellyfish, corals, and sea anemones. Blastozoans are diploblastic, meaning they have two primary germ layers: the ectoderm and the endoderm. The ectoderm gives rise to the outer covering and the nervous system, while the endoderm forms the inner lining of the body cavity and the digestive system.

Blastozoans are typically marine, although some freshwater species exist. They are often sessile or slow-moving, with a simple body plan that allows for efficient filter feeding or predation. The group is notable for its diversity in terms of body forms and feeding strategies, ranging from the simple, gelatinous jellyfish to the complex, colonial corals. Despite their simplicity, blastozoans have played a significant role in the evolution of animal life, providing insights into the early development and diversification of animals.