DEFINITIONS AND KEY POINTS FOR OBJECTIVES
| TERMS DEFINITIONS | |
| Coelom | A coelom is a body cavity that arises in mesoderm and is lined by a sheet of mesoderm called the peritoneum. |
| Protostomes | The animals in which blastopore tbrin mouth are called |
| Deutrostomes | The animals in which blastopore forms anus and mouth formed as a secondary opening are called deutrostomes. |
| Schizocoelous | The animals which are formed by the splitting of mesoderm are called schizocoelous. | |
| Enterocoelous | The animals in which coelom are formed by invagination of enteron or gut are called enterocoeious. | |
| Mantle | Mantle of molluscs is attached to the visceral mass. It enfolds most of the body. It secreted a shell that overlies the mantle. | |
| Tuksion | Torsion is a 180°, counterclockwise twisting of the visceral mass. mantle, and mantle cavity. | |
| Protandric | In this case. testes develop first, and after they degenerate. Then ovaries become mature. | |
| Valves | The two convex halves of the shell are called valves. | |
| Umbo | The oldest part of the shell is called umbo. Umbo is a swollen area near the shell’s anterior margin. | |
| Pseudofeces | The rejected material, called pseudofeces. | |
| Peln | The shell of a squid is reduced. It has internal, chitinous structure called the pen. | |