The goldfish (Carassius auratus) is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is one of the most commonly kept aquarium fish. A relatively small member of the carp family (which also includes the Prussian carp and the crucian carp), the goldfish is native to east Asia. It was first selectively bred in China more than a thousand years ago, and several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration and colouration (various combinations of white, yellow, orange, red, brown, and black are known).
Mechanical digestion is the physical breaking down of food particles into smaller food particles to increase surface area for chemical digestion. Chemical digestion is the use of enzymes to break down polymers into monomers (through the breaking of chemical bonds)
While there is variation among the types of biological polymers found in different organisms, the chemical mechanisms for assembling and disassembling them are largely the same across organisms. Monomers are generally linked together through a process called dehydration synthesis, while polymers are disassembled through a process called hydrolysis. Both of these chemical reactions involve water. In dehydration synthesis, bonds are formed linking monomers together while losing water molecules. In hydrolysis, water interacts with a polymer causing bonds that link monomers to each other to be broken.