These creatures do absorb nutrients and oxygen directly through their thin skin, needing no heart or circulatory system

These animals distribute oxygen and nutrients through their skin by diffusion, with no need for a heart or circulatory system

These sea creatures use a water vascular system for movement and nutrient distribution, eliminating the need for a heart

These echinoderms rely on their water vascular system for movement and nutrient transport, making a heart unnecessary

These simple organisms transport nutrients and oxygen via water flow through their porous bodies. So they do not need a heart or circulatory system

These anthozoans absorb nutrients through polyps from surrounding water, requiring no heart due to their simple structure

These creatures take in nutrients and oxygen from water, and don't need a heart due to their simple anatomy

These parasitic organisms absorb nutrients directly from their host’s intestines, relying on diffusion instead of a heart

These segmented worms have aortic arches that pump blood, serving a similar function as a traditional heart

These flatworms absorb oxygen and nutrients through diffusion, so they don't require a heart or blood vessels