My Research Question: What are the differences of the digestive systems of man, birds, insects and reptiles?

Firstly, before we even start on the differences of the digestive system, we must know what is the definition of the digestion. Basically, there are two different types of digestion, mainly mechanical and chemical breakdown of food into simpler and smaller components, so as to let the food to be able to be absorbed into the bloodstream and used by the body. Whole food is taken in at one end and waste expelled from the other. Enroute, nutrients are taken out of the food and absorbed into the bloodstream according to the body's needs. The whole process is called digestion. The whole process of digestion involves many organs, which are called the Digestive System. There are also other organs involved in supporting the digestive process as well, but are not technically considered part of the digestive system, these organs are the liver, gallbladder and pancreas (for humans). For other animals like, reptiles or birds or insects I am not sure, so it brought up this research question. In the next few posts, I will be telling you about the different digestive systems of humans, birds, insects and reptiles.