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An Introduction to Zoology:  Chapter 6
An Introduction to Zoology: Chapter 6
Published by The Lone Ranger
Default Gastrulation

Gastrulation results in the formation of two embryonic germ layers, the inner endoderm and the outer ectoderm. The endoderm surrounds the archenteron, which will eventually become the animalís digestive tube. The opening into the archenteron is the blastopore.

In diploblastic animals, the endoderm and the ectoderm are the only germ layers, and all adult tissues develop from those two embryonic tissues. In most diploblastic animals, there is only one opening into the digestive system, and so that opening functions both as the mouth and the anus.

In triploblastic animals, a third layer of tissue forms between the endoderm and the ectoderm, the mesoderm. Most of the internal organs form from mesodermal tissue, while the blastopore forms either the mouth or the anus, depending on whether the animal is a protostome or a deuterostome.


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By monruw on 03-30-2011, 01:55 PM
Default Re: An Introduction to Zoology: Chapter 6

why it's called animal-vegetal axis? sound like kinda food, meat and vegetable or what else~ any story behind this?
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By The Lone Ranger on 05-22-2011, 01:35 AM
Default Re: An Introduction to Zoology: Chapter 6

"Vegetal," is related to "vegetable." Many plants can reproduce asexually, whereas virtually all animals reproduce sexually.

Probably for this reason, "vegetal" came to refer to processes in living things that are "plant-like," especially processes that do not occur through sexual reproduction. More to the point, perhaps, plants generally grow much more slowly than do animals. So the "vegetal" pole of an egg gets its name for the fact that the cells in this region grow and divide much more slowly than do the cells in the "animal" pole.


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