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Platyzoa
The "Platyzoa" are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes (or flatworms), and a new phylum, the Acanthognatha, into which he gathered several previously described phyla of microscopic animals. Later it has been described as paraphyletic, containing the Rouphozoa and the Gnathifera. Since 2022 it is believed that Platyozoa are monophyletic and also includes Mesozoa. Phyla One scheme placed the following phyla in Platyzoa: * Rouphozoa ** Platyhelminthes ** Gastrotricha * Gnathifera ** Syndermata *** Rotifera *** Seisonida ** Acanthocephala ** Gnathostomulida ** Micrognathozoa ** Cycliophora Characteristics None of the Platyzoa groups have a respiration or circulation system because of their small size, flat body or parasitic lifestyle. The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share characteristics such as the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flatworm
Platyhelminthes (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a Phylum (biology), phylum of relatively simple bilaterian, Segmentation (biology), unsegmented, soft-bodied invertebrates commonly called flatworms or flat worms. Being acoelomates (having no coelom, body cavity), and having no specialised circulatory system, circulatory and respiratory system, respiratory organ (anatomy), organs, they are restricted to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food can not be processed continuously. In traditional medicinal texts, Platyhelminthes are divided into Turbellaria, which are mostly non-parasitic animals such as planarians, and three entirely parasitic groups: Cestoda, Trematod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platyhelminthes
Platyhelminthes (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called flatworms or flat worms. Being acoelomates (having no body cavity), and having no specialised circulatory and respiratory organs, they are restricted to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food can not be processed continuously. In traditional medicinal texts, Platyhelminthes are divided into Turbellaria, which are mostly non- parasitic animals such as planarians, and three entirely parasitic groups: Cestoda, Trematoda and Monogenea; however, since the turbellarians have since been proven not to be monophyletic, this classification i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathifera (phylum)
Gnathifera (from the Greek '' gnáthos'', “jaw”, and the Latin '' -fera'', “bearing”) is a clade of generally small spiralians characterized by complex jaws made of chitin. It comprises the phyla Gnathostomulida, Rotifera and Micrognathozoa. Chaetognatha has recently been recognised as closely related to the group, with it either being included within Gnathifera or the broader group Chaetognathifera. Gnathiferans include some of the most abundant phyla. Rotifers are among the most diverse and abundant freshwater animals and chaetognaths are among the most abundant marine plankton. Description In most gnathiferans, the anus opens on the dorsal surface of the animal. In micrognathozoans and gnathostomulids, the anus is transient and only forms during defecation. Unlike other gnathiferans, in chaetognaths and the extinct '' Amiskwia'' the anus is located on the ventral surface in a subterminal position. Both Gnathostomulida and Micrognathozoa are acoelomates, rotife ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic grouping (a clade) includes a common ancestor and ''all'' of its descendants. The terms are commonly used in phylogenetics (a subfield of biology) and in the tree model of historical linguistics. Paraphyletic groups are identified by a combination of synapomorphies and symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term received currency during the debates of the 1960s and 1970s accompanying the rise of cladistics, having been coined by zoologist Willi Hennig to apply to well-known taxa like Reptilia (reptiles), which is paraphyletic with respect to birds. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrognathozoa
''Limnognathia'' is a genus of microscopic acoelomate freshwater animal that was discovered in Disko Island, Greenland, in 1994. Since then, it has also been found on the Crozet Islands of Antarctica as well as in the British Isles and the Spanish Pyrenees, suggesting a worldwide distribution. There are two known species of ''Limnognathia'': ''L. maerski'', described in 2000, and ''L. desmeti'', described in 2025. ''Limnognathia'' is the only genus in the phylum Micrognathozoa ("small-jawed animal"). Description Feeding ''Limnognathia'' mainly feeds on bacteria, blue-green algae, and diatoms. It has very complex jaws, with fifteen separate elements; these elements are very small, ranging from 4 μm to 14 μm. The animal can extend part of its jaw structure outside its mouth while eating. It also extends much of its jaw structure outside its mouth when it is regurgitating indigestible items. Anatomy ''Limnognathia'' has a large ganglion, or 'brain', in its he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syndermata
Syndermata is a clade of animals that, in some systems, is considered synonymous with Rotifera. Older systems separate Rotifera and Acanthocephala as different phyla, and group them both under Syndermata., p. 788ff. – see particularly p. 804 This clade is placed in the Platyzoa. Phylogeny Phylogenetic analysis of the 18S ribosomal gene has revealed that the Acanthocephala, formerly considered a separate phylum are most closely related to the rotifers. They are possibly closer to the two rotifer classes Bdelloidea and Monogononta than to the other class, Seisonidea, producing the names and relationships shown in the cladogram below. A study of the gene order in the mitochondria suggests that Seisonidea and Acanthocephala are sister clades and that the Bdelloidea are the sister clade to this group. This has since been corroborated by the discovery of a fossil stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animal
Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, have myocytes and are motility, able to move, can reproduce sexually, and grow from a hollow sphere of Cell (biology), cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million extant taxon, living animal species have been species description, described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from to . They have complex ecologies and biological interaction, interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudobiceros Bedfordi
''Pseudobiceros'' is a genus of flatworms. Like all flatworms, Pseudobiceros are hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...s. This particular genus engages in penis fencing. When the "winner" touches its penis to the "skin" of the other, insemination occurs, and the "loser" has to bear the burden of motherhood. Species The following species are recognised in the genus ''Pseudobiceros'': *'' Pseudobiceros apricus'' Newman & Cannon, 1994 *'' Pseudobiceros bajae'' ( Hyman, 1953) *'' Pseudobiceros bedfordi'' ( Laidlaw, 1903) *'' Pseudobiceros brogani'' Newman & Cannon, 1997 *'' Pseudobiceros caribbensis'' Bolanos, Quiroga & Litvaitis, 2007 *'' Pseudobiceros cinereus'' (Palombi, 1931) *'' Pseudobiceros damawan'' Newman & Cannon, 1994 *'' Pseudobiceros dendriticus' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyly
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent common ancestor (or more precisely an ancestral population), i.e. excludes non-descendants of that common ancestor # the grouping contains all the descendants of that common ancestor, without exception Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic'' grouping meets 1. but not 2., thus consisting of the descendants of a common ancestor, excepting one or more monophyletic subgroups. A ''polyphyletic'' grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
