The difference between protostomes and deuterostomes is protostomes have only an ectoderm and endoderm protostomes have only a mesoderm protostomes develop a mouth first and then an anus protostomes develop an anus first and then a mouth

the cell theory states that all living things including animals, as well as plants, are made of cells.

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.