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Invertebrates

A deck of flashcards for Undergraduate Study of Biology.

QuestionAnswer
Three ways of cellularization of multicellular organisms Three way which a multicellular organism can evolve from a protists: Symbiotic, Colonial and "Cellularization."
Symbiotic cellularization Protists can symbiotically group to form composite organism. It may have genetic problems and evidence.
Colonial cellularization Divided cells of single protist could remain together after the division. This is the most favoured, cellularization of multicellular organisms.
"Cellurization" Multinucleate protists (cells with more than one nucleous) could evolve internal membranes. However, there is little evidence for internal division.
What are the closest animals regarded as colony of protists rather than multicellular? Sponges.
Symmetry There are four types of possible symmetry: Asymmetry, spherical symmetry, radial symmetry and bilateral symmetry.
Radial symmetry Lines of symmetry in vertical plants, typical of phyla of sessile or floating organism (Cnidaria and Echinodermata).
Bilataeral symmetry Found in free mobile organisms (anterior and posterior ends) and dorsal and ventral surfaces. Only one plane divides the animal into summetrical halves.
Cephalization The development of bilatal symmetry is linked to diretional movement; sense organs are concentrated at the anterior end of organism. Feeding apparatus and brain development and the formation of a head.
Coelom The principal body cavity in most animals, located between the intestinal canal and the body wall.
Pseudocoelom A second body cavity (the first being the gut) which occupies a space between the mesoderm of the body wall and the endoderm of the gut.
Three types of coelomic forms Acoelomate, pseudocoelomate and coelomate.
Acoelomate Body volume filled with mesenchyme and other tissue
Pseudocoelomate Body space is fluid-filled but not formed from the mesoderm and not lined by cellular peritoneum; derived from blastocoel.
Coelomate With fluid filled body cavity from mesodermal sources; derived from cavitation of blocks of mesoderm (schizocoel) or by the formation of sacs of mesoderm from the annchenteron (entercoel).
Homologous structures
Analogous structures
Coelom formation from Protostomes Coelom forms by a splitting of the mesoderm.
Coelom formation from Deuterostomes Coelom forms by an out-pocketing of primitive gut
Protostome A multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusc, or arthropod.
Deuterostomes Embryonic development, the first opening (the blastopore) becomes the anus, while in protostomes, it becomes the mouth.
Cleavage in Protostome and Deuterostome Spiral cleavage (Protosome) and Radial cleavage (Deuterostome).
Fate of embryonic cells in protosome and deuterostome Protostomes undergo determinate development where the 4 cell embryo excise one cell and the development arrests. Deuterostomes undergo indeterminate development where the 4 cell embryo exise one cell and develops into normal embryos.
Fate of blastopore in protosome and deuterostome Blastopore of protostomes becomes the mouth. Blastopore of deuterostome become anus.
Formation of mesoderm and coelom in protosomes The formation of mesoderm is from the mass of cells near blastopore and the coelom is formed schizocoely.
Formation of mesoderm and coelom in deuterostomes The formation of the mesoderm is from the cells pinched off of archenteron and the coelom is formed enterocoely.
Created by: theecloud
 

 



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