Jumat, 27 Agustus 2010

Introduction Coelenterata

CHAPTER I
INTRODUCTION

Coelenterata is an obsolete long term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies). The name comes from the Greek "koilos" ("full bellied"), referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, external and internal. The shape of its body is radially symmetrical, diploblastic multicellular animals with a tissue grade of organisation. They are able to life at aquatic, freshwater or marine solitary or colonial forms which may be free swimming or sedentary. Their body has a mouth at the oral end which leads into a spacious cavity called gastrovascular cavity or coelenteron. Presence of long, hollow structures called tentacles used for locomotion and food capturing. Presence of peculiar type of cells called cnidoblasts, nematocysts or stinging cells in the ectoderm, especially in the tentacles, used for offence and defence. Digestion is both intracellular and extracellular.Respiration and excretion by simple diffusion. Presence of a network of nerves spread all over the body. Many forms exhibit polymorphism, wherein different types of individuals are present in a colony for different functions. These individuals are called Zooids. Reproduction asexually (external budding) or sexually (formation of gametes).
Coelenterata is one of invertebrate phylum which is able to give adventages for human. For instance, Aurelia aurita as the member of coelenterata can be used as human food. Besides that, the member from class anthozoa, can be a beautiful coral reef as the place of some fishes in a sea park. Hence, the sea park is able to make the tourists are interested to visit and see the beauty of those colourful anthozoa. It is important for us to learn more about the diversity of coelenterata, in order that we are able to understand about the way to make it more useful for human. Hence, it will be a wise choice for us to do the experiment of invertebrate zoology which is entitled "Coelenterata".

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