Answer:
The circulatory system, also known as the cardiovascular system, is a simple loop which starts, and ends, with your heart. It is a closed system, meaning blood does not enter or leave the system during its journey from your heart to your body and back again.
Explanation:
Answer:
They can move about freely.
They can reproduce.
They can respond to internal stimulus.
Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or changed, by the body into moving mechanical energy and heat energy. People have invented ways to use the chemical energy of substances to power machines.