The World Around Us!

Porifera is a sponge, they are Asymmetrical and are Sessile. Sessile means they are fixed in one place and are immobile. Porifera do not have a nervous system. They are the only multicellular animal without a nervous system. Porifera digestive system filters food into the ostia and flows out of the osculum. They rely on weather for their food and oxygen. Porifera excretory system is diffusion which allows the sponge to absorb oxygen from the water, ammonia and carbon dioxide are diffused and goes to the surrounding water. Porifera doesn't only use diffusion for its excretory system but it also uses it for its circulatory system. This is because porifera do not have blood and water passes through cells. Porifera also uses diffusion for it's respiratory system. Porifera skeletal system is absent. Porifera is reproductive system when sexual is both male and female. When sperm is released it travels to a female. When a sexual gemmules which are internal buds grow. They reproduce using mass of cells.

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Their are three different classes.

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Hexactinellida has four to six pointed siliceous spicule. Glass sponges  can't contract and is found in antarctic.

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Demospongiae is the most diverse class. Demospongiae is 90% of all species. They are made up of silica and spongin fibers.

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Calcarea spicules made of calcium carbonate it is in the form of calcite or aragonite and is normally found in the tropics.

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Porifera is latin for beating pores. 99% of porifera live in marine water. Some of them are fresh water.

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Spicules are structural elements in most sponges. Specules provide support.