Coelomate and Acoelomate

Topics: Developmental biology, Annelid, Zygote Pages: 2 (634 words) Published: April 14, 2001
Most animal phyla originated in a relatively brief span of geological time, however the diversity among them is extraordinary. Every organism is very unique a detailed in certain ways, comparisons of certain types of organisms can be very difficult. The class in which will be compared is that of the invertebrates. The main difference between coelomate and acoelomate body plans are that coelomates have a true coelom, which is a fluid-filled body cavity completely lined by tissue which is derived from mesoderm. The purpose of this cavity is to cushion the suspended organs to help them prevent injury, enables internal organs to grow and move independently from the outer body wall. Acoelomates, though, lack a cavity between the digestive tract and the outer body wall. An example of an acoelomate would be a flatworm, or planarian, While an example of a coelomate would be a rotifer. The differences between protostome and deuterostome development are the characteristics in their cleavage, their coelom formation, and the fate of their blastopore. Many protostomes undergo spiral cleavage. In spiral cleavage, planes of cell division occur diagonal to the vertical axis of the embryo. The cleavage also determinates, which casts the developmental fate of each embryonic cell very early. In deuterostomes, they undergo radial cleavage, where the cleavage planes are either parallel or perpendicular to the vertical axis of the egg. Deuterostomes are further characterized by indeterminate cleavage, which means that each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo. Indeterminate cleavage of the human zygote allows identical twins to be possible. In a protostome, as the archenteron forms, solid masses of mesoderm split to form the coelomic cavities, or schizocoelous development. In deuterostomes, the development of body cavities, or enterocoelous, happens when the mesoderm buds from the wall of the archenteron...
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