👉 The term "metatherian" is a medical term that describes an organism that has no heart. It refers to any type of animal, including humans and other primates, which lack the function of a heart, making it impossible for them to survive without external assistance or medication. Metatherians are classified into two main categories: those with a single ventricle (like humans) and those with multiple ventricles (like bats). In humans, the absence of a heart results in life