Question

In what way the excretory system is developed from protozoa to
Annelida?​

Answer 1

Answer:

Because one-celled organisms are in constant contact with their environment, they do not need excretory organs. However, multicellular organisms need a mechanism to carry waste products from cells to the external environment. Flatworms, such as planaria, have a series of excretory cells called flame cells. Flame cells contain cilia that direct water and metabolic wastes to enter the cells and pass into excretory canals. The excretory canals join with other canals to form excretory tubules. Fluid from the excretory tubules leaves the body through pores.