Jellyfish Essays - Developmental Biology, Zoology, Biology

Jellyfish - Because Cnidarians, including jellyfish, have two primary germ layers, they are considered dibloblastic . - Jellyfish are not the only example of radially symmetric organisms in the world. In fact, most members of the phylum to which jellyfish belong, HYPERLINK "http://animaldiversity.org/accounts/Cnidaria/" \t "_blank" Cnidaria , exhibit radial symmetry, including most hydras, corals and sea anemones. The only other animals with this type of symmetry are echinoderms - Cephalization is the concentration of sensory organs as well as a brain in a specified head area. The anterior, or head, is where the sensory cells and organs, clusters of nerve cells, and organs for ingesting food are located. The posterior is on the opposite end of the cephalized animal, which may have a tail. Jellyfish do not have a brain, so they would not be considered cephalized . - A few animals, such as jellyfish and related creatures, are diploblasts . That means that they developed from only two basic tissue layers: the ectoderm and the endoderm. A coelom is the gut of tripolblasts . It is a completely encased, fluid-filled body cavity lined by mesodermic tissue. You will often see literature classifying animals as having or not having a coelom. The majority of animal phyla have coeloms. (Study.com 2014) - Cnidaria (Jellyfish) No Segmentation Habitat : Jellyfish are found in all of the Earth's oceans, including the very deep sea, as well as shallow saltwater lakes. Locomotion: Most jellyfish are essentially passive drifters carried along by currents; therefore even large jellyfish are classified as planktonic. Though mostly purely planktonic, most have structures that allow them to change direction and move up or down in the water column and some can even swim against weak currents. Body Systems and Adaptations : Most jellyfish do not have specialized digestive , osmoregulatory , central nervous , respiratory , or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, often surrounded by oral arms, which connects with the mouth/anus at the base of the bell. (Wiki 2015)