Why are sponges cnidarians flatworms and roundworms limited to life in water or moist environments?

Sponges, cnidarians, flatworms, and roundworms are limited to aquatic or moist environments primarily due to their physiological adaptations and reliance on water for key life processes. These organisms often lack specialized respiratory and circulatory systems, relying on diffusion for gas exchange and nutrient transport, which necessitates a moist environment to facilitate these processes. Additionally, many of these species have permeable bodies that can easily lose water, making survival in drier conditions challenging. Overall, their reproductive and developmental stages also often require aquatic habitats for successful completion.