Sponges and coelenterates: porous and sac-like animals

[Music] each of these animals a sponge and a jellyfish is a member of the invertebrates the animals without backbones the jellyfish is one of the sacklike animals called cerates another group of invertebrates are the sponges called porifera porifera means por Bearer sponges are porous animals Just One Step Beyond a colony of independent cells though some sponges live in fresh water most species are found in the ocean sponges are found in various sizes and shapes this common bath or horny sponge has a soft body and an outer protective covering here we can see the porous structure after sponges are removed from the water they are dried and then trimmed to prepare them for commercial use this dry portion of the horny sponge is a kind of pliable skeleton the skeleton is composed of fibers of a material called spongin spongin is a secretion of the cells the skeleton of the calcarius sponge has no fibers it is made up of needle likee Limestone spikes called spicules the skeleton of the celicious sponge has glasslike spicules a portion of this horny sponge has been cut away so we may view the interior of the sponge body the pores located in the body wall of the sponge are the openings of canals which lead from the outer layer to the inner layer of cells these canals lead to the gastral cavity a large cavity located in the center of the sponge when the moving fella of the color cells of the inner layer create a current water is drawn through the pores through the canals and into the gastral cavity the water is forced out through the osculum the opening at the top of the sponge releasing a few drops of dye shows us how the sponge draws in food particles and oxygen that are in the Water waste products are expelled through the top in contrast to these simple digestive processes the reproductive processes are more complex since sponges reproduce both sexually and asexually asexual reproduction occurs when buds grow on a sponge here a bud is growing on the parent animal sponges also reproduce asexually by regeneration if a sponge is cut into pieces each piece will continue to grow each piece of a horny sponge may be fastened to a rock to Anchor It To The Sea bottom the piece will continue to grow into a new sponge sponges also reproduce sexually as we'll see in this cross-section drawing the spero or a sperm cell from one sponge may enter another in the water current passing into a canal the sperm cell is captured by a holding cell the ovam or egg cell enlarges after you uniting with the sperm cell the fertilized egg or zygote gradually develops into a free swimming larvae that moves out of the sponge this is the microscopic sponge larvae when this larvae settles down and becomes firmly attached it grows into a young sponge the sponge with a basic structure of two layers of cells is among the simplest of the many celled animals the structure of sponges enables them to carry on division of labor among their specialized cells an important characteristic of the many celled animals like the sponge the jellyfish is also a many celled invertebrate this common jellyfish is an Orelia it is one of the group of sacklike animals called cerates the jellyfish swims by alternately relaxing and Contracting its bell-shaped body the water environment supports its soft sacklike body located in the center of the animal is the internal cavity of a jellyfish the gastrovascular cavity here food enters by a four cornered mouth which we see as a very small opening these four horseshoe-shaped bodies are the sexual organs the jellyfish and other cerates have two layers of cells the outer layer or ectoderm is a protective covering the inner layer or endoderm lines the internal cavity at its sexual stage the aelia produc produces a ciliated larvae called a planula this grows into a pop a small body with tentacles now the aelia enters its asexual stage as the aelia pop feeds and grows it buds off into small pops like itself in the winter season the pop develops constrictions until it resembles a series of discs on a one by one the dis- likee pups pinch off from the parent each one develops into an adult jellyfish other common cerates found in Shallow Marine water are the coral forming animals known as Coral polyps these tiny tuik animals the corals secrete Limestone billions of corals over a long period of time secrete skeletal material of limestone which builds up into coral reefs corals are strikingly beautiful and have various forms colors and shapes the C anemones are another class of cerates this cross-section of anemon shows its muscular sacklike body the tentacles at the top thrust food into the gastrovascular cavity by means of a basal disc the anemon can slide about very slowly like most other cerates anemones May reproduce sexually and asexually anemones are among the most highly specialized cerates living in Sal water the most common freshwater cerate is a tiny animal called a Hydra like the cemon the Hydra has a gastrovascular cavity two layers of cells and a basil disc that anchors the animal a Hydra reproduces asexually by forming buds a bud appears as a branch growing out from the side of the adult later the bud separates from the parent and grows into a new Hydra sexual reproduction occurs in Autumn the eggs in the female Hydra are produced in the ovaries small swellings along the body wall in the testes of the male Hydra sperm cells develop like all cerates the Hydra has a simple nervous system if a tentacle of an extended Hydra is touched by a needle all the tentacles and the body contract such a response is possible because the stimulus is carried by a nerve net a series of nerve cells lying in the middle layer of the body the Hydra has a basic structure similar to that of other cerates a structure characterized mainly by a sacklike body sponges on the other hand are characterized by a porous structure nevertheless these two groups of animals have four common characteristics inner and outer layers of cells division of labor among the cells and sexual reproduction as well as asexual reproduction these aquatic animals the sponges and the cerates are are the simplest of the multicellular animals and represent two groups of [Music] invertebrates