Sponges are the simplest form of multi-cellular animals. They are very diverse and come in a large variety of colours, shapes and structural complexities. They range in heights of 1-200cm and in diameters of 1-150cm. They have partially differentiated tissues, and not true tissues. Sponges don’t have internal organs. They don’t have muscles, a nervous system, or a circulatory system. Their walls are lined with many small pores called ostia that allow water flow into the sponge.   

Sponges live in all types of regions all over the region. They are able to thrive in most environments. 99% of all sponges live in marine water, but some sponges made of spongin fiber live in freshwater. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponge individuals and sponge species in the tropics of all regions because the water is warmer. They like to live in clearer waters over murky waters formed by currents. The murky waters may often clog the pores on the sponges so the sponge cannot get its nutrition and oxygen to survive.