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Invertebrates
A deck of flashcards for Undergraduate Study of Biology.
| Question | Answer |
|---|---|
| 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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