OverviewThe organisms in this phylum are radially symmetrical, which means that the parts of the body extend outward from the center like the spokes on a wheel. All cnidarians possess tentacles with stinging cells on the tips which are used to capture and subdue their prey. These stinging cells are called cnidocytes and contain a structure known as a nematocyst, which is a coiled thread-like stinger. All cnidarians also have the following characteristics:
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Coral (Anthozoa)Corals are calcium carbonated organism that reside at the bottom of the ocean. When carbon dioxide is released in the atmosphere and oceans, respiration can occur in a coral. The coral removes oxygen byproduct during the day when photosynthesis is occurring, which helps it breath. At night, respiration takes place, and the coral instead uses the carbon dioxide to breathe. More oxygen is produced than absorbed, and thus, extra oxygen is leftover.
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Jellyfish (Scyphozoa)Jellyfish breathe using oxygen, similar to corals. Oxygen is absorbed into the jellyfish by sucking in oxygen through its skin and also through diffusion. The oxygen is absorbed into the ectoderm, or first layer of skin. From there, it goes through to the endoderm, or second layer. These oxygen molecules can then be used,and excess oxygen is released as carbon dioxide.
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Box Jellyfish (Cubozoa)Box jellyfish also breathe through their bodies. They use their coelenteron, or internal cavity, to inhale oxygen. The walls of the body are very thin, and as a result, the oxygen is able to easily diffuse into the internal organs of the box jellyfish. In addition, their cells are able to absorb oxygen and extract carbon dioxide from their bodies.
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