where do they live
Porifera means pore-bearing. Sponges are covered with tiny pores on the outside called ostia (2). Ostia lead to an internal system of canals which leads to one or more larger holes called oscula, which are the openings to the out side. Ostia are surrounded by donut shaped cells called porocytes. The chambers within the canals are lined up with cells called choanocytes, or collar cells. The collar cells consist a sticky funnel shaped collar and a hair-like whip called a flagellum. The collar cells beat their flagella back and forth to force the water through the sponge. The water brings in nutrients and oxygen and takes out the carbon dioxide. The two purposes of providing food and removing wastes are served due to this function. The sticky collars also pick up tiny particles of food and bacteria brought in by the water (2).
Unlike the cells of most other animals, the cells of sponges do not form into various organs like kidney, liver, or nerves. Sponge cells are totipotent (Dawkins 2004). The totipotent cells could give rise to reproductive cells or other types of cells of the organism. In theory, this enables a sponge to live forever (Dawkins 2004).
Sponges can produce sexually as well as asexually. Most sponges are hermaphroditic, which means each adult can act as either female or male. Asexual reproduction happens by budding and fragmentation (4). With this type of reproduction pieces or fragments of the sponge's body are broken off the by the water currents, and they are carried by the currents to a different location. There they attach themselves to the ocean floor and grow to be an adult sponge. Some of the sponges form internal buds, called gemmules. These can survive even extremely unfavorable conditions. They survive even after the rest of the sponge dies due to the unfavorable conditions (4).
Sexual reproduction happens internally. The male acting sponge cells release the gametes into the water. From there the sperm travels closer to the female acting sponge cells, where it is picked up by the female acting sponge’s choanocytes or the collar cells, which then lose their collars and become special amoeba-like cells that carry the spermatazoa to the eggs, and fertilization then takes place (4). The tiny larvae which are the result of fertilization are released into the water. The larvae use their cilia to propel themselves through the water. Eventually they settles down and grow to be an adult sponge. Next time around when they reproduce the sponges may change roles; the sponge that played male could play female and vice versa (4).
The evolution of multi cellular sponges from single-celled protozoa is one of the landmark events in evolution. This is the origin of the Metazoa, or multicellular organisms (Dawkins 2004). An experiment performed by H. V. Wilson of the University of North Carolina was published in the 1907 issue of the Journal of Experimental Zoology (Wilson 1907). He separated the cells of a living sponge by forcing it through a fine sieve. The separated cells were let out onto a saucer containing sea-water. Most of them were single cells. After a while Wilson observed that the cells behaved like individual beings or amoebas. They were crawling on the bottom of the saucer, and they started joining up to form agglomerations of cells. Eventually they grew to become whole new sponges. When Wilson tried to mash up two different species of sponges together, the separated cells mixed only with their own species. They did not mix with the other kind of species. This experiment may shed some light on how multi cellular animals formed initially. The first sponge may have been a colony of protozoans that happened to be together by chance (Dawkins 2004).
Even though the sponges don’t have nerves and muscles, the individual cells can sense and react to the changes in the surrounding environment. The cell layers are loose conglomaration of cells. They are not really tissues as they are unspecialized. The colonial protists called choanoflagellates live in the bottom of ponds and shallow areas. Biologists think that sponge choanocytes are very similar to choanoflagellate cells, and they believe that it is highly likely that sponges arose from choanoflagalllates that lived in late Precambrian seas. Biologists believe that the molecular evidence points to ancient choanoflagallates as close relatives of the ancestor of all animals.
from byhttp://tolweb.org/treehouses/?treehouse_id=4291
Unlike the cells of most other animals, the cells of sponges do not form into various organs like kidney, liver, or nerves. Sponge cells are totipotent (Dawkins 2004). The totipotent cells could give rise to reproductive cells or other types of cells of the organism. In theory, this enables a sponge to live forever (Dawkins 2004).
Sponges can produce sexually as well as asexually. Most sponges are hermaphroditic, which means each adult can act as either female or male. Asexual reproduction happens by budding and fragmentation (4). With this type of reproduction pieces or fragments of the sponge's body are broken off the by the water currents, and they are carried by the currents to a different location. There they attach themselves to the ocean floor and grow to be an adult sponge. Some of the sponges form internal buds, called gemmules. These can survive even extremely unfavorable conditions. They survive even after the rest of the sponge dies due to the unfavorable conditions (4).
Sexual reproduction happens internally. The male acting sponge cells release the gametes into the water. From there the sperm travels closer to the female acting sponge cells, where it is picked up by the female acting sponge’s choanocytes or the collar cells, which then lose their collars and become special amoeba-like cells that carry the spermatazoa to the eggs, and fertilization then takes place (4). The tiny larvae which are the result of fertilization are released into the water. The larvae use their cilia to propel themselves through the water. Eventually they settles down and grow to be an adult sponge. Next time around when they reproduce the sponges may change roles; the sponge that played male could play female and vice versa (4).
The evolution of multi cellular sponges from single-celled protozoa is one of the landmark events in evolution. This is the origin of the Metazoa, or multicellular organisms (Dawkins 2004). An experiment performed by H. V. Wilson of the University of North Carolina was published in the 1907 issue of the Journal of Experimental Zoology (Wilson 1907). He separated the cells of a living sponge by forcing it through a fine sieve. The separated cells were let out onto a saucer containing sea-water. Most of them were single cells. After a while Wilson observed that the cells behaved like individual beings or amoebas. They were crawling on the bottom of the saucer, and they started joining up to form agglomerations of cells. Eventually they grew to become whole new sponges. When Wilson tried to mash up two different species of sponges together, the separated cells mixed only with their own species. They did not mix with the other kind of species. This experiment may shed some light on how multi cellular animals formed initially. The first sponge may have been a colony of protozoans that happened to be together by chance (Dawkins 2004).
Even though the sponges don’t have nerves and muscles, the individual cells can sense and react to the changes in the surrounding environment. The cell layers are loose conglomaration of cells. They are not really tissues as they are unspecialized. The colonial protists called choanoflagellates live in the bottom of ponds and shallow areas. Biologists think that sponge choanocytes are very similar to choanoflagellate cells, and they believe that it is highly likely that sponges arose from choanoflagalllates that lived in late Precambrian seas. Biologists believe that the molecular evidence points to ancient choanoflagallates as close relatives of the ancestor of all animals.
from byhttp://tolweb.org/treehouses/?treehouse_id=4291