How do different organisms carry out excretion?

Different organisms carry out excretion in the following manner: 

1. Unicellular organisms have contractile vacuoles which collect and discharge waste products outside the cell. 

2. Excretion in sponges takes place by diffusion of waste material in water. This waste is discharged through the osculum.

3. True organs of excretion are found in those animals that show bilateral symmetry. 

4. The most common type of excretory organ is a simple or branching tube that opens to the exterior, through pores called nephridiopores. This system is generally found in some annelids, Amphioxus, earthworms, etc. 

5. In most of the insects, excretion takes place by a set of blind ended tubules called malpighian tubules. 

6. Crustaceans have green glands as excretory organs. 

7. Members of phylum Echinodermata do not have any specialised excretory organs. Waste materials directly diffuse into water or are excreted through tube feet. 

8. The mammalian kidneys are a collection of functional units called nephrons, which are well designed to excrete metabolic waste.