Flatworms

invertebrates · ocean life · simple animals · weird biology

Flat as pancakes. Flatworms are so flat and thin that oxygen and nutrients can pass right through their bodies by diffusion, kind of like how a sponge soaks up water. Their flat shape is the secret to their survival.

No special organs. Unlike you, flatworms don't have lungs, hearts, or blood vessels. They don't need them because their flat bodies are so thin that everything they need can get in and out on its own.

One opening, one job. Flatworms have only one hole that does double duty: it's where food goes in AND where waste comes out. This means they can't eat and poop at the same time like we do.

Nice and simple. Flatworms are bilaterian animals, which means they have a left and right side that match. But they're still way simpler than most other animals because they have no real bones or blood system.

No body cavity. Flatworms have no space inside their bodies for organs to nestle into, because they're acoelomates. This might sound limiting, but it works great for such tiny, flat creatures.