Create a new account

It's simple, and free.

Details

  • 10 Pages
  • 2582 Words

Did Paleozoic Corals Have Zooxanthellae? The Ph

Did Paleozoic Corals Have Zooxanthellae?

The Phylum Cnidaria can be traced from the late Proterozoic to the Holocene. Several major geologic boundaries occur throughout that span of time. The temporal intervals are often based on biological extinction and radiation events. For example, the Paleozoic begins at the Precambrian/Cambrian boundary and ends at the Permian/Triassic boundary. Analyses of carbon-12/carbon-13 data suggest that these boundaries were characterized by major alteration of the earth's biomass. Various Paleozoic Cnidaria corals became extinct at the end of the Permian. Whether or not these extinct corals gave rise to later orders remains uncertain. Certainly there are some significant differences between the Paleozoic corals and the zooxanthellate corals.

At one time, corals, sea anemones, and jellyfish were all grouped together with the ctenophores in the Phylum Coelenterata. More recently, however, these organisms have been classified as Cnidaria. This medium-sized phylum contains a large number of both solitary and colonial invertebrates (Oliver & Coates, 1987, p. 140). Although the animals occur in most aquatic environments, their fossils have only been found in marine sedimentary rocks.

The Cnidaria typically have primary radial symmetry and are, for the most part, anatomically simple. They have no specialized cells which are grouped into organs like those found in higher animals. Rather, their different cell types occur in only two body layers. The organisms are, therefore, diploblastic. The outer ectoderm and inner endoderm develop from the embryo and are divided by a jelly-like, middle noncellular layer. At the base of the outer cell layer, this structureless mesoglea contains a simple nerve net. The Cnidaria have no mesoderm or coelum. Epithelial, muscular, and connective tissue differentiation all occurs within the two primary body layers. In addition, Cnidaria have evol...

Page 1 of 10 Next >

More on Did Paleozoic Corals Have Zooxanthellae? The Ph...

Loading...
APA     MLA     Chicago
Did Paleozoic Corals Have Zooxanthellae? The Ph. (1969, December 31). In LotsofEssays.com. Retrieved 10:32, March 29, 2024, from https://www.lotsofessays.com/viewpaper/1708653.html