Sponges

Sponges are classified as animal because of the fact that they are //multicellular// and //heterotrophic.// They also have no cell walls yet, have a few specialized cells. Sponges are asymmetrical with no front,back,left, or right sides. They have **choanocytes** which are specialized cells that use the hair-like flagella to move a current of water through the sponge.This water enters through ores in the body wall. The flow of water provides simple mechanisms for the sponges basic functions such as f//eeding//, //circulation//, //respiration,// and //excretion//. Sponges can reproduce either sexually or asexually. In most species, a single sponge forms both the eggs and sperm producing them at different times. In sponges the eggs are fertilized through **internal fertilization**. This is a process where sperm are released from one sponge and then are carried by water currents until they enter another sponge's pores. After th fertilization, the zygote develops into a larva. The larvae eventually end up settling on the sea floor. Sponges produce asexually by producing gemmules. When the sponge goes through **budding**, part of the sponge breaks off of the original and grows into a sponge once it settles tor the seafloor. Some sponges produce **gemmules** which go through any harsh environment to grow into a new sponge when conditions are favorable
 * Sponges** are the most simple and likely the most unusual animals known. To us humans they are best known in their dried form, natural sponges used for bathing. Sponges have tiny openings, or pores, all over their bodies and they live their entire adult life in a single spot which makes them sessile.