Pertanyaan

Sponges or Porifera are a group of animals that included about 10,000 diving species. Adult sponges are sessile animals that attach to hard rocky surface shells or submerges objects. The larvae are ciliatec free-swimming creatures. Most sponges inhabit marine environment, but a few species live in freshwater habitats. There are three subgroups of sponges, the glass sponges, the demosponges and the calcarious sponges Sponges are primitive multicellular animals that have no digestive system, no circulatory system and no nervous system. They do not have organs and their cells are not organized into well-refined tissues, The body of a sponge is like a say that is perforated with lots of small opening or pores Sponges are filter feeders. They draw water in through the pored located throughout their body wall into a central cavity. The central cavity is lived with collar cells which have a ring of tentacles that surrounds a flagellum. Movemnet of the flagellum created curent that keeps water blowing through the central cavity and out of a hole at the top of the sponge called the osculum. As water passed over the collar cells, food is captured by the collar cells ring of tentacles. Once absorbed, food is digested in food vacuoles or transferred to the amoeboid cells in the middle later of the body wall for digestion What is the main idea of paragraph two?