Question

What is digestion?Why do only animals require a digestive system?Concise Biology Class IX By H.S. Vishnoi CHAPTER 13-DIGESTIVE SYSTEM

Answer 1

Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms,these smaller substances are absorbed through the small intestine into the blood stream..
Animals require a digestive system because they take food in the form that body cannot directly utilize. The food needs to be broken down into form that body can utilize. Therefore digestive system becomes very important animals. There are various other organisms apart from animals that possess a digestive system For example amoeba has food vacuole that helps in digestion. 

Answer 2

Animals require digestive system as the food that they eat ,that cannot be utilized as such in the body . It must be changed into a soluble form before it is absorbed into blood and distributed