Germ Layers: Cnidarians are diploblastic animals, i.e., derived only from two embryonic germ layers, viz., ectoderm and endoderm. All cnidarians show the presence of two membrane layers in the body that are derived from the endoderm and ectoderm of the embryo. Can you find the hydra tentacles? Term. Gonozooid. 4. A specialized polyp within a hydrozoan colony that forms only medusae or gametes. Inside of Mesoglae (sac) is the GVC. Gastrovascular cavity: Definition. How many germ layers does the hydra contain? Cnidaria also depend on the cilia that line the GVC to move fluid and nutrients throughout the body. How many tentacles does your hydra specimen contain? Acoelomate vs. Coelomate vs. Pseudocoelomate: Many animals have a body cavity. Cnidarians are carnivorous animals that possess muscle, nervous, reproductive and digestive tissues. Level of Organization: They are the first multicellular animals from evolution point of view which show tissue level of organization. Explain the movement of the hydra if live specimens are available. They are diploblastic animals and have a more complex level of organization than Porifera. 6. ... Cnidaria have no organs (at the tissue level of organization) Term. Figure 15.2.4: Cnidarians have two distinct body plans, the (a) medusa and the (b) polyp. Name the stinging cells present on the tentacles that are unique to cnidarians. The representatives of Phylum Cnidaria have radial or biradial symmetrical body. 4.12): The epidermis contains a collection of different types of cells. Cnidaria have two germ layers and they are the endoderm and ectoderm. Endoderm. Body wall (Fig. All cnidarians have two tissue layers, with a jelly-like mesoglea between them. In other cnidarians, both a polyp and medusa form exist, and the life cycle alternates between these forms. Endomesoderm. A germ layer in animal embryos that can give rise to either endoderm or mesoderm. Muscle tissues (ectodermal) Definition. Examine slides of Hydra (phylum Cnidaria, a diploblastic animal) and Lumbricus (the common earthworm, phylum Annelida, a triploblastic animal) and see if you can identify and label the tissue layers. The body wall of a cnidarian consists of three layers, an outer layer known as the epidermis, a middle layer called the mesoglea, and an inner layer referred to as the gastrodermis. What type of symmetry is seen in the hydra? Type of Symmetry: The animals within phylum Cnidaria have Radial symmetry. 5. connects with the outside through the mouth. jelly-like layer between 2 germ layers. Circulatory System: Cnidaria do not have a circulatory system but it is replaced by diffusion across different germ layers, including that of the GVC. The outer tissue layer of a cnidarian polyp, larva or medusa. % a sac. Which phyla have only two germ layers? About 99 % cnidarians are marine species and few inhabit in freshwater. Hermaphrodite. The inner tissue layer of a cnidarian polyp, larva or medusa. 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