Sponges

Sponges are also Known as Porifera, they are the most primitive invertebrate organisms. They were produced by a group of primitive multicellular organisms and formed an independent branch during the evolution. There are about 10,000 known species of sponges. Unlike other invertebrates, most sponges live in the ocean, and only a few live in fresh water. Living sponges have a variety of body colors, ranging from yellowish brown, orange to purple, and body heights ranging from 1 to 200cm. Their shapes include flat, spherical, barrel-shaped, pot-shaped, etc.
Sponges are fixedly attached to the seabed to survive. They use flagella on the inner body wall to communicate and generate water flow in the water. The water flow is added to the sponge body through the numerous water inlet pores (Ostia) on the porous surface of the sponge to filter and absorb the food contained in the water. It is then eliminated from the body through the Osculum. This simple cycle is the way sponges exist.
The psychological structure system of sponges is very simple. And in the stage where organs have not yet been produced, the mechanism is still at the structural level. The cavity of a sponge is one or more radially symmetrical or erroneously symmetrical. The cavity is composed of two cell layers, which are the endodermis and the outer cortex. Their endoskeleton is called a "spicule". Or "Spongin", some species have both. Sponge species are distinguished by the shape of their endoskeleton and can be divided into three classes:
1. Calcarea ):This class of sponges are calcium carbonate spicules. They are small in size and mostly live alone. They are relatively primitive species and are scattered in shallow waters and intertidal areas on the coast of the mainland. There are about 50 species.
2. Thexactinellida:The sponges of this class are silica spicules, also known as "Glass Sponges". They are of ordinary size and live in water depths of 500 meters. -In the 1,000-meter deep sea, most of them live alone, and there are about 450 species.
3. Demonspongiae: There are many types of sponges in this class, with about 9,500 species. Except for a few species, most of them have bones.The skeleton is made of single or four-sided silicon spicules, organic sponge fibers, or both, but it is definitely not as good as calcium-free spicules and six-fold silicon spicules. A small number of species are produced in freshwater, most of which are marine. They often grow collectively and have unclear individual boundaries.

                    </p>

                </p>