Question

True or false: even single celled organisms have a circulatory system similar to humans.

Answer 1

False

A single-celled organism doesn't need a circulatory system as human do. Since they are singular, they can interact with their environment directly. Unlike them, a multicellular organism like a human has a part where their cells can't get oxygen or food directly, thus need to be supplied by the circulatory system. Some of the cells also well differentiated so it only accept a certain processed food.