flatworms

Flatworms are soft, flattened invertebrates belonging to the phylum Platyhelminthes. They have bilateral symmetry, meaning their body has mirror-image sides, and lack a true body cavity. Flatworms can be free-living or parasitic; some live on aquatic surfaces, while others infect humans and animals. They have a simple digestive system with a single opening and a nervous system with a ladder-like arrangement of nerve cords. Flatworms are important in ecosystems as decomposers and as part of the food chain. Their simple body structure makes them interesting models for studying regeneration and development.