Porifera are commonly referred to as sponges. An early evolutionary event in the history of animals may have separated the sponges from other metazoans, and from there the sponges have traveled their own separate evolutionary way.
They are frequently placed in their own subkingdom, Parazoa. This means "beside the animals". Until the nineteenth century, sponges were considered a plant-animal, because during their adult life they are attached to something else, like a rock and are not free to move about.
Fossil sponges are among the oldest known animal fossils. The living sponge species are classified in the phylum Porifera, which is composed of three distinct groups, the Hexactinellida (glass sponges), the Demospongia, and the Calcarea (calcareous sponges). There is a fourth, small group, known as Sclerospongiae, which has the characteristics of all three of the other groups combined, but it is generally not mentioned as a major group.
Sponges don't have a digestive system. they don't have a stomach, intestines, and organs like that. In fact, sponges don't have any organs at all. Their bodies consist of cells that are not organized into tissues or organs. The body of a sponge is like a sac that is perforated with lots of small openings or pores. The body wall consists of three layers. An outer layer of flat epidermal cells, a middle layer that consists of cells that migrate within the layer, and an inner layer that consists of cells and collar cells. Sponges are filter feeders. They take in water through the pores all over their body wall into a central cavity. The central cavity is lined with collar cells which have a ring of tentacles that surround a flagellum. Movement of the flagellum creates current that keeps water flowing through the central cavity and out of a hole at the top of the sponge called the osculum. Food is captured by the collar cell's ring of tentacles. Food is digested in food vacuoles or transferred to the amoeboid cells in the middle layer of the body wall for digestion.
The water current also delivers a constant supply of oxygen to the sponge and removes waste products.
Sponges have no organs or digestive system but can still feed on particles as small as bacteria, and are extremely efficient filterers.
They are frequently placed in their own subkingdom, Parazoa. This means "beside the animals". Until the nineteenth century, sponges were considered a plant-animal, because during their adult life they are attached to something else, like a rock and are not free to move about.
Fossil sponges are among the oldest known animal fossils. The living sponge species are classified in the phylum Porifera, which is composed of three distinct groups, the Hexactinellida (glass sponges), the Demospongia, and the Calcarea (calcareous sponges). There is a fourth, small group, known as Sclerospongiae, which has the characteristics of all three of the other groups combined, but it is generally not mentioned as a major group.
Sponges don't have a digestive system. they don't have a stomach, intestines, and organs like that. In fact, sponges don't have any organs at all. Their bodies consist of cells that are not organized into tissues or organs. The body of a sponge is like a sac that is perforated with lots of small openings or pores. The body wall consists of three layers. An outer layer of flat epidermal cells, a middle layer that consists of cells that migrate within the layer, and an inner layer that consists of cells and collar cells. Sponges are filter feeders. They take in water through the pores all over their body wall into a central cavity. The central cavity is lined with collar cells which have a ring of tentacles that surround a flagellum. Movement of the flagellum creates current that keeps water flowing through the central cavity and out of a hole at the top of the sponge called the osculum. Food is captured by the collar cell's ring of tentacles. Food is digested in food vacuoles or transferred to the amoeboid cells in the middle layer of the body wall for digestion.
The water current also delivers a constant supply of oxygen to the sponge and removes waste products.
Sponges have no organs or digestive system but can still feed on particles as small as bacteria, and are extremely efficient filterers.