Amoebozoa – Wikipedia
The Amebozoi I am an important clade of Protozoi Ameboids, understanding the majority of those who move by means of an internal cytoplasmic flow. Their pseudopods are typically smoothed and similar to fingers, called lobopods. Most are unicellular, and are common in the soils and aquatic habitats, with some found, such as symbipons of other organisms, including several pathogens. Amebozoa also include melmic molds, multinucleate or multi -cellular shapes that produce spores and are usually visible to the naked eye.
Amebozoa vary considerably in terms of size. Many are only 10-20 microns of size, but also include many of the largest protozoa. The famous species Amoeba proteus It can reach 800 microns in length, and in part due to its size it is often studied as a representative cell. Multinucleate Amebe such as Chaos It is Pelomyxa They can be of several millimeters of length, and some muddy molds cover several square meters.
The cell is usually divided into a central granular mass, called endoplasma, and a transparent external layer, called ectoplasma. During the Endoplasma locomotion it flows forward and the ectoplasma flows back along the external part of the cell. Many Amebe move with a front and rear defined, in essence, the cell works as a single pseudopodo. They usually produce numerous transparent projections called subpseudopodes (or certain pseudopods), which have a defined length and are not directly involved in locomotion.
Other Amebozoa can form more indeterminate pseudopods, which are more or less tubular and are largely filled with granular endoplasm. The cellular mass flows into a main pseudopodo, and the others basically portrayed unless you change direction. The subpseudopods are generally absent. In addition to the few naked shapes such as Amoeba and Chaos, the group includes many anebozoa with shell. These can be made up of organic materials, such as in the Arcella genre, or particles collected cemented together, as in that spreads, with a single opening from which pseudopods come out.
The main power mode is phagocytosis: the cell surrounds the particles of potential food, keeping them in these vacuoles where they can be digested. Some Amebe have a rear bulb called Uroide, which they can use to accumulate waste and periodically detach from the cell. When food is scarce, many species can form cysts, who transported from the air, make them know new environments. In muddy molds, these structures are called spores, and form in structures with stem called fruits or sporangi bodies.
Most of the Amebozoa do not have flagelli and, more generally they do not produce structures supported by micro -tubes, except during mitosis. However, the Archamoebae group present Flagelli, and the muddy molds generate many biflagellated gametes. Flagelli are generally anchored by a micro -tubile cone, suggesting a close opistoconti relationship. The mitochondrias typically have branched tubular ridges, but they have been lost by the archiamebe.
Amebozoa are difficult to classify, and the relationships within the group remain confused.
It seems (based on protooms) that form a group of brother of animals and mushrooms, diveting from this line after they had divided from the plants [first] , as illustrated below:
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Strong similarities between Amebozoi and opistoconti (animals including mushrooms), led to the proposal that they form a clade called Unikonta.
Amebozoi Bosi [ change | Modifica Wikitesto ]
Traditionally all the amebe with lobose pseudopods have been treated together in the lobose class, placed with other ameboids in the Sarcina or Rhizopoda phylum, but these have been considered unnatural groups. Structural and genetic studies have identified the percolzoi and the different architects as independent groups. In the phylogenesis based on RRNA, their representatives were separated from the other Amebe, and it appeared that they diverge close to the basis of the evolution of eukaryotes, as for most of the muddy molds.
However, phylogenetic trees reviewed by Cavalier-Smith and Chao in 1996 [2] They suggested that the remaining loboses form a monofiletic group, and that the architects and micezoa are closely related to it, even if the perolzoi are not. Subsequently they proposed amoebozoa as a phylum major to refer to this supergroup [3] . Studies based on other genes have provided strong support for the unit of this group [4] . Patterson treated most of them together with what they call ” Testate Philosis Amobe ” come ” Ramicristates ” [5] , on the basis of mitochondrial similarities, but the latter have now been moved to the Cercozoa group.
The lobose subgroup is paraphiletic. Two large classes of lobose have been identified, the tubulinea and flabellinea, but various others remain of uncertain location.
Other amebozoi [ change | Modifica Wikitesto ]
The Archiamebe and Micetozoi have been placed in a conesteen subphylum. This classification receives support from molecular phylogenesis.
Vase microfossils discovered all over the world show that Amebozoi exist from the neopro -nopotoial era. Fossils of the species Melanocyrillium hexodiadema , Palaeoarcella Athanata It is Hemisphereeriella decorated they come from 750 million years rocks. All three fossils have an hemispherical form, inordinated opening and regular recesses, which resemble very modern arcellinids, which are amoeboids with shell. There P. Athanata , in particular, has the same aspect of the existing genus Arcella. [6] [7]
- ^ L. EICICHINER, J.A. Pachebat; Glöckner; M. A.Randream; R. SUCGANG; M. RORRIMAN; J. Song; R. Olsen; K. Szafranski; Q. XU;, The genome of the social amoeba Dictyostelium discoideum , in Nature , vol. 435, n. 7038, 2005, pp. 43–57, doi: 10.1038/nature03481 .
- ^ T.Cavalier-Smith & E. E. Chao, Molecular phylogeny of the free-living archezoan Trepomonas agile and the nature of the first eukaryote , in Journal of Molecular Evolution , vol. 43, 1996, pp. 551–562, two: 10.1007/BF02202103 .
- ^ T.Cavalier-Smith, A revised six-kingdom system of life , in Biological Reviews of the Cambridge Philosophical Society , vol. 73, 1998, pp. 203–266, two: 10.1017/S0006323198005167 .
- ^ S. L. Baldauf et al , A kingdom-level phylogeny of eukaryotes based on combined protein data , in Science , vol. 290, 2000, pp. 972–977, two: 10.1126/science.290.5493.972 .
- ^ David J. Patterson, The Diversity of Eukaryotes , in American Naturalist , vol. 145, 1999, pp. S96–S124.
- ^ Porter, H. Susannah, Meisterfeld, Ralf, and Knoll, H. Andrew, Vase-shaped microfossils from the Neoproterozoic Chuar Group, Grand Canyon: a classification guided by modern testate amoebae , in Journal of Paleontology , vol. 77, n. 3, 2003, pp. 409–429.
- ^ ( IN ) M. Susannah Porter, The Proterozoic Fossil Record of Heterotrophic Eukaryotes , in Neoproterozoic Geolobiology and Paleobiology , vol. 27, 2006, pp. 1–21, two: 10,1007/1-4020-5202-2_1 . URL consulted on 11 September 2009 (archived by URL Original on September 25, 2019) .
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