Why is circulatory system absent in Flatworm?
A flatworm is, as the name indicates, flat. Since the organism’s body is so flat, it only consists of a thin layer of tissue. This tissue is able to directly absorb and transport nutrients throughout its body from cell to cell without a circulatory system’s aid. To contrast this, we have a circulatory system because for our body to diffuse nutrients from our intestinal tract from one cell to another would take forever – imagine trying to get glucose to your brain! The circulatory speeds up the process by transporting nutrients and such through the blood. However, there is no need with the flatworm considering comparitively it is much smaller and is also able to directly absorb nutrients from the environment.