How and from where did eukaryotic organelles arise?
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The origin of the eukaryotic cell was a milestone in the evolution of life, since they include all complex cells and multi-cellular organisms. The timing of this series of events is hard to determine; Knoll (1992) suggests they developed approximately 1.6 - 2.1 billion years ago. Fossils that are clearly related to modern groups start appearing around 800 million years ago.\n\nrRNA trees constructed during the 1980s and 1990s left most eukaryotes in an unresolved "crown" group (not technically a true crown), which was usually divided by the form of the mitochondrial cristae. The few groups that lack mitochondria branched separately and so the absence was believed to be primitive, but this is now considered an artifact of long branch attraction and they are known to have lost them secondarily.\n\nTrees based on actin and other genes have painted a different and more complete picture. Most eukaryotes are now included in several supergroups:\n\nOpisthokonts Animals, fungi, choanoflagellates, etc. \nAmoebozoa Most lobose amoebae and slime moulds \nRhizaria Various amoeboid protozoa \nExcavates Various flagellate protozoa \nArchaeplastida Land plants, green and red algae \nHeterokonts Brown algae, diatoms, water molds, etc. \nAlveolates Ciliates, Apicomplexa, dinoflagellates, etc. \n\nThe heterokonts and alveolates may be part of a larger group that is ancestrally photosynthetic, called the chromalveolates, but this remains contentious. Otherwise the relationships between the different supergroups are mostly uncertain, and in particular there is dispute about where the root of the evolutionary tree belongs, and as a result what the earliest eukaryotes were like. A few small protist groups have not been related to any of the major supergroups, notably the centrohelids, apusozoans, and ebriids.\n\nEukaryotes are closely related to archaea, at least in terms of nuclear DNA and genetic machinery. In other respects, such as membrane composition, they are similar to eubacteria. Three main explanations for this have been proposed:\n\nEukaryotes resulted from the complete fusion of two or more cells, the cytoplasm forming from a eubacterium and the nucleus from an archaeon (alternatively a virus). \nEukaryotes developed from Archaea, and acquired their eubacterial characteristics from the proto-mitochondrion. \nEukaryotes and Archaea developed separately from a modified eubacterium. \nThe origin of the endomembrane system and mitochondria are also disputed. The phagotrophic hypothesis states the membranes originated with the development of endocytosis and later specialized; mitochondria were acquired by ingestion, like plastids. The syntrophic hypothesis states that the proto-eukaryote relied on the proto-mitochondrion for food, and so ultimately grew to surround it; the membranes originate later, in part thanks to mitochondrial genes (the hydrogen hypothesis is one particular version).
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The endosymbiotic theory states that higher order organisms (read eukaryotes) developed over time as a symbiotic relationship developed between earlier prokaryotic organisms. This is most routinely applied to the conceptual arrangements surrounding chloroplasts and plant cells and mitochondria and all cells. The theory states that a free living organism in the prokaryotic lineage developed a capacity for absorbing another energy producing type of organism. The interaction was able to provide a survival advantage for the newly formed organism and thus was maintained. Mitochondria do contain their own genome, but their array of required proteins come from both the mitochondrial genome and the nuclear genome.
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hes wrong (above. Prokaryotes do have organelles. THey do not have membrane bound organelles. Take for example the central vacuole of a plant. It has a membrane surrounding it, so it is not a prokaryote. Prokaryotes have ribosomes which synthesize proteins and nucleic acids to form a polypeptide chain. THey have a mitochondria for ATP etc..
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Magnetosomes are membranous bacterial organelles sharing many features of eukaryotic organelles. Using electron cryotomography, we found that magnetosomes are invaginations of the cell membrane flanked by a network of cytoskeletal filaments. The filaments appeared to be composed of MamK, a homolog of the bacterial actin-like protein MreB, which formed filaments in vivo. In a mamK deletion strain, the magnetosome-associated cytoskeleton was absent and individual magnetosomes were no longer organized into chains. Thus, it seems that prokaryotes can use cytoskeletal filaments to position organelles within the cell.
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Prokaryotes (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos, pl. -otes; also spelled "procaryotes") are organisms without a cell nucleus (= karyon), or indeed any other membrane-bound organelles, in most cases unicellular (in rare cases, multicellular). This set of characteristics is distinct from eukaryotes (also spelled "eucaryotes"), organisms that have cell nuclei and may be variously unicellular or multicellular. The difference between the structure of prokaryotes and eukaryotes is so great that it is considered to be the most important distinction among groups of organisms. Most prokaryotes are bacteria, and the two terms are often treated as synonyms. However, Woese has proposed dividing prokaryotes into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the significant genetic differences between the two. This arrangement of Eukaryota, Bacteria, and Archaea is called the three-domain system. This replaces the two-empire system.\n\nhttp://en.wikipedia.org/wiki/Prokaryote\n\n\nA eukaryote (IPA: [juːˌkarɪəʊt]), also spelled eucaryote, is an organism with a complex cell or cells, in which the genetic material is organized into membrane-bound nucleus/nuclei. Eukaryotes comprise animals, plants, and fungi—which are mostly multicellular—as well as various other groups that are collectively classified as protists (many of which are unicellular). In contrast, prokaryotes are organisms, such as bacteria, that lack nuclei and other complex cell structures. Eukaryotes share a common origin, and are often treated formally as a superkingdom, empire, or domain. The name comes from the Greek ευ, meaning good, and κάρυον, meaning nut, in reference to the cell nucleus).\n\nhttp://en.wikipedia.org/wiki/Eukaryote\n\nMORE STUFF ON LINKS
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Nucleus contains the genetic material and is where mRNA is produces for later production of protein, which occurs at the rough endoplasmic reticulum.  THe mitochondria carries out respiration, while the chloroplast does the same using light. There are a number of others, of course, but that'll get you started.
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plant cells form a disk during the final splitting phase, while animal membranes constrict.  Also, it is easier to see earlier in animals, and animals have centrioles, plants dont.  thats all my textbook says.  the phases and everything are the same, though.
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Both are eukaryotic (containing a "true nucleus").  \n\nAnimal Cells lack a cell wall and adjacent cells are connected by junctions (adhesive, gap or tight).  Animal cells contain centrioles (help create microtubules used in mitosis and meiosis) and lysosomes (organelles used to digest wastes and old organelles). During telophase and cytokinesis the cells separate via a cleavage furrow.\n\nPlant Cells contain a cell wall (think of the cell wall as the "skeleton" composed mainly of cellulose) and rely on turgor pressure to keep them upright.  Adjacent cells are connected by channels called plasmodesmata.  You will not find centrioles or lysosomes in a plant cell, but you will find a really cool organelle called a large centrol vacuole.  This organelle is where the water is stored in a cell and it helps maintain the turgor pressure described above.  It also acts as a lysosome, storing chemicals and waste products.  The Central vacuole can also store the pigments you see in flowers as well as poisons used to deter predators.  And of course, in a plant cell you will find the plasts as mentioned by someone earlier.. including the famous chloroplasts (the site for photosynthesis) as well as the chromoplasts (contain pigments) and amyloplasts (specialized for starch storage). During telophase and cytokinesis, the cells are separated by a structure called a cell plate.   \n\nUmmm, that's all I can come up with right now!
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No, there isn't. Please please please bear in kind that helminths and fungi are EUKARYOTIC.
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Mitochondria are found in nearly all EUKARYOTIC cells, usually several or many per cell.\n\nAnything not considered a eukaryote does not in turn have organelles therefore it doesn't have mitochondria.\n\nDan is correct viruses and prokaryotes don't have them.....
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Nuclear?  Nuclear envelope?  Nuclear membrane? \n\nThe word 'eukaryote' means 'true nuclei'.  They are talking about the membrane which surrounds the nucleus of the cell.  This is not present in Prokaryotes.
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They are eukaryotic, multicellular, and in the kingdom Animalia. They come from mammals (you and me) and so that means they have an membrane enclosed nucleus, as opposed to prokaryotic cells that don't have a nucleus.  They are multicellular b/c all animals are.  And the kindom Animalia applies cheek cells as well. :)
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None-- But the endoplasmic reticulum does come in contact at various times during the life cycle
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B) Membrane-bound organelles\nThe procariotic cells are like a water-filled baloon, they are just a cover with water and other things (of course, this is only an example), while eukaryotic cells have compartiments.\nEvery cell has DNA, that's the way information is passed from cell to cell when they reproduce.\nRibosomes are important for producing proteins, every cell has to have them, even if with time they lose them.\nCytoplasm is the 75% of every cell, it's basically water, proteins and other things.
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============================================================\nMitosis is a special kind of cell division used by eukaryote cells. You will probably find a series of diagrams in your biology text book to show the stages of mitosis; these are:\n\nprophase \nmetaphase \nanaphase \ntelophase \n============================================================\n============================================================\n2. cell division \n\neukaryotic cell \n\na. By mitosis (def).\nb. Sex cells in diploid (def) organisms are produced through meiosis (def). \n\nprokaryotic cell \n\na. Usually by binary fission (def). No mitosis.\nb. Organisms are haploid (def). No meiosis needed. \n============================================================\n\nMore at the links:
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the first multicellular being was Dictyostelium from symbiotic realtionship
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plant cells have vacuoles and chloroplasts while animal cells dont. plant cells synthesize their own foods while animal cells dont.\n\nribosomes are the organelles that synthesize proteins using RNA from the nucleus.\n\nI just cant seem to remember what the answer of the third question was.