The Science Explorer Series Level 1 Issue 5 : Scary Monstrous Tree by Young Scientists

A system is a whole consisting of parts that work together to perform a function(s). There are natural systems as well as man-made systems. Examples of systems in nature are the digestive and respiratory systems. Examples of manmade systems are electrical and decimal systems. Understanding these systems allows Man to understand how they operate and how parts influence and interact with one another to perform a function.