Phylum Porifera
Phylum Porifera
Phylum Porifera: All sponges belong to this phylum. Sponges are aquatic animals which remain fixed to the bottom of the sea or some object. Such animals are called sessile. Most sponges are marine. Sponges can be of many shapes—round, sac like or branched. They are multicellular, but there is very little division of functions between the cells.
Therefore, the cells are not organized into tissues.These animals do not have a nervous system. A very special feature of sponges is the circulation of water throughout their body cavity which is called the spongocoel. Water, carrying nutrients and oxygen, enters through pores, called ostia, all over the body. It circulates in the body cavity and leaves it through a large pore called the osculum. This is the way a sponge feeds. They have a hard outer layer, or skeleton. The skeleton of sponges is formed of needle-like structures called spicules. One class of sponges called chalk sponges has calcerous made of calcium carbonate) spicules. In glass sponges the spicules are siliceous (made of silica) and in horny sponges the spicules are of spongin fibre (proteinaceous).
Examples : Sycon( Scypha), Sopngilla(fresh water sponge), Euspongia(bath sponge), Euplectella aspergillum(Venus flower basket).
The skeleton of sponges is consist of needle like structures called as _______________ | |||
| Right Option : A | |||
| View Explanation | |||
Of the animal group listed below, which one evolved first ? | |||
| Right Option : B | |||
| View Explanation | |||
Sponges have originated from ____________ | |||
| Right Option : D | |||
| View Explanation | |||
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