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Introduction |
Introduction |
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Animalia is the name of the animal kingdom in standard taxonomy, coming directly from the Latin animalis, which in turn comes from anima. Also the title of a book by [Graeme Base]? full of illustration and aliteration: see [Graeme Base/Animalia]?. |
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Animalia is the name of the animal kingdom in standard taxonomy, coming directly from the Latin animalis, which in turn comes from anima. Also the title of a book by [Graeme Base]? full of illustration and aliteration: see [Graeme Base/Animalia]?. |
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Blah, blah, blah. Yahooo!!! |
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Development and evolution |
Development and evolution |
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Animals are eukaryotes, and diverged from the same group of flagellate protozoa that gave rise to the fungi and choanoflagellates?. The last are especially close relatives, with collared cells appearing only among them, the sponges, and rarely in certain other animal forms. In all these groups motile cells have a single posterior flagellum with similar ultrastructure. |
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Animals are eukaryotes, and diverged from the same group of flagellate protozoa that gave rise to the fungi and choanoflagellates?. The last are especially close relatives, with collared cells appearing only among them, the sponges, and rarely in certain other animal forms. In all these groups motile cells have a single posterior flagellum with similar ultrastructure. |
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Adult animals are typically diploids, producing small motile sperm and large non-motile eggs. In all forms the fertilized zygote intiallvy divides to form a hollow sphere called a blastula. This then undergoes rearrangement and differentiation. Blastulae are probably representative of the sort of colonies animals evolved from; similar forms occur among other flagellates, e.g. Volvox. However none of these other groups really ever progressed further, and large multicellular forms tend to develop by progressive growth instead. |
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Adult animals are typically diploids, producing small motile sperm and large non-motile eggs. In all forms the fertilized zygote intiallvy divides to form a hollow sphere called a blastula. This then undergoes rearrangement and differentiation. Blastulae are probably representative of the sort of colonies animals evolved from; similar forms occur among other flagellates, e.g. Volvox. However none of these other groups really ever progressed further, and large multicellular forms tend to develop by progressive growth instead. |
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Classification |
Classification |
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In Linnaeus' original scheme, the animals were one of three kingdoms, divided into the classes of Vermes?, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, whereas the various other forms have been separated out. When they were first discovered, the Protozoa were included as an animal phylum or subkingdom, but as they are generally unrelated and often as similar to plants as animals, a new kingdom, the Protista, was devised to hold them. |
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In Linnaeus' original scheme, the animals were one of three kingdoms, divided into the classes of Vermes?, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, whereas the various other forms have been separated out. When they were first discovered, the Protozoa were included as an animal phylum or subkingdom, but as they are generally unrelated and often as similar to plants as animals, a new kingdom, the Protista, was devised to hold them. |
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Phylum Ectoprocta? |
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Traditionally the Arthropoda - the largest animal phylum including insects, spiders, crabs, and kin - and two small phyla related thereto, the Onychophora? and Tardigrada?, have been held to be close relatives of the annelids on account of their common segmented body plan. This relationship is now in doubt, and it appears that the arthropods may instead belong with various pseudocoelomate worms - the Nematoda? (roundworms), Nematomorpha? (horsehair worms), Kinorhyncha?, Loricifera?, and Priapulida? - that share with them the characteristic of moulting. |
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Traditionally the Arthropoda - the largest animal phylum including insects, spiders, crabs, and kin - and two small phyla related thereto, the Onychophora? and Tardigrada?, have been held to be close relatives of the annelids on account of their common segmented body plan. This relationship is now in doubt, and it appears that the arthropods may instead belong with various pseudocoelomate worms - the Nematoda? (roundworms), Nematomorpha? (horsehair worms), Kinorhyncha?, Loricifera?, and Priapulida? - that share with them the characteristic of moulting. More work will be needed to resolve between these possibilities. |
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