Explain The Digesive Tract And Circulatory System Among Different Animals?

Digestive tract is defined as the path through which food travels and goes through the various processes like absorption, digestion and elimination. Animals included under coelenterates and flat worms have single opening for ingestion and egestion. This single opening is known as mouth. This type of digestive system is of incomplete type. Animals included under mammals and round worms have two openings for ingestion and egestion. These openings are known as mouth and anus. This type of digestive system is of complete type. Circulatory system helps in the flow of blood. It is of two types. It can be closed or open type. In closed system blood is confined in the blood vessels with no direct contact with the body cells. It includes annelids and chordates. In open system blood is not confined in the blood vessels and has a direct contact with the body cells. It includes arthropods and molluscs. Sinuses and lacunae are included in it. Blood may be colorless, blue or red in color. The blue color is due to pigment haemocyanin and red color is due to the pigment haemoglobin. Some of the organisms like Taenia have no circulatory system.