|
Dasycladales
Dasycladales is an order of large unicellular green algae in the class Ulvophyceae. It contains two families, the Dasycladaceae and the Polyphysaceae. These single celled algae are from 2 mm to 200 mm long. They live on substrates in shallow warm (>20°C) euhaline tropical marine waters, usually less than 20 meters deep, and protected from waves. They are very large cells. They are able to attain these sizes without numerous internal cell wells because they build calcium carbonate shells around themselves. They contain only one nucleus in their vegetative stage, which remains in the bottom of the cell in the holdfast at the substrate. Only when they are ready to produce gametes does the nucleus undergo meiosis and then numerous mitoses into many nuclei which then migrate into the gametangia at the top of the alga. Because the nucleus is safely hidden in the holdfast, the cells easily regenerate if the top portions are broken off. These algae are notable for h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dasycladales
Dasycladales is an order of large unicellular green algae in the class Ulvophyceae. It contains two families, the Dasycladaceae and the Polyphysaceae. These single celled algae are from 2 mm to 200 mm long. They live on substrates in shallow warm (>20°C) euhaline tropical marine waters, usually less than 20 meters deep, and protected from waves. They are very large cells. They are able to attain these sizes without numerous internal cell wells because they build calcium carbonate shells around themselves. They contain only one nucleus in their vegetative stage, which remains in the bottom of the cell in the holdfast at the substrate. Only when they are ready to produce gametes does the nucleus undergo meiosis and then numerous mitoses into many nuclei which then migrate into the gametangia at the top of the alga. Because the nucleus is safely hidden in the holdfast, the cells easily regenerate if the top portions are broken off. These algae are notable for h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ulvophyceae
The Ulvophyceae or ulvophytes are a class of green algae, distinguished mainly on the basis of ultrastructural morphology, life cycle and molecular phylogenetic data.Graham LE, Graham JM, Wilcox LW (2009) ''Algae''. 2nd Edition. Benjamin Cummings (Pearson), San Francisco, CA The sea lettuce, ''Ulva'', belongs here. Other well-known members include ''Caulerpa'', ''Codium'', ''Acetabularia'', ''Cladophora'', '' Trentepohlia'' and ''Monostroma''. The Ulvophytes are diverse in their morphology and their habitat. Most are seaweeds such as those listed above. Others, such as '' Rhizoclonium'', '' Pithophora'' and some species of ''Cladophora'' live in fresh water and in some areas are considered weeds. Evolution The origin and early diversification of the Ulvophyceae likely took place in the late Neoproterozoic. Although most contemporary ulvophytes are marine macroalgae (seaweeds), ancestral ulvophytes may have been freshwater, unicellular green algae. Molecular phylogenetic evide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyphysaceae
The Polyphysaceae is a taxonomic family of green algae, one of three families in the order Dasycladales Dasycladales is an order of large unicellular green algae in the class Ulvophyceae. It contains two families, the Dasycladaceae and the Polyphysaceae. These single celled algae are from 2 mm to 200 mm long. They live on substrates .... For single-celled organisms, they are huge, growing to nearly a foot long in some cases. References External links Dasycladales Ulvophyceae families {{Ulvophyceae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclocrinitids
Cyclocrinitids are an early (mid-Ordovician–early-Silurian) Dasycladalean algae, resembling but probably not closely related to the Receptaculitids. References Dasycladales {{silurian-plant-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Receptaculitid
''Receptaculites'' is the name-bearing genus for an extinct group of conspicuous benthic marine genera, the receptaculitids (formally Receptaculitaceae or Receptaculitidae), that lived from the Early Ordovician through the Permian period, peaking in the Middle Ordovician. The group's phylogenetic origin has long been obscure, with some arguing that they were calcareous algae, probably of the order Dasycladales.Byrnes, J.G. 1968. Notes on the nature and environmental significance of the Receptaculitaceae. Lethaia, vol. 1, p. 368-381. Receptaculitids lived in warm, shallow seas, but consensus disagreeing. They have been described from all continents except Antarctica. In some areas they were important reef-formers, and they also occur as isolated specimens. ''Receptaculites'' and its relatives have a double-spiral, radiating pattern of rhombus-shaped plates supported by spindle-like objects called meroms. Fossils can usually be identified by the intersecting patterns of clockwise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dasycladaceae
The Dasycladaceae is one of the two extant families of green algae of the order Dasycladales. When found in Palaeozoic limestones, they typically indicate depositional depth of less than 5m.See the NCBI The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...br>webpage on Dasycladaceae Data extracted from the Genera * †'' Acicularia'' * †'' Acroporella'' * '' Amicus'' * '' Anatolipora'' * '' Andrusoporella'' * '' Anfractuosoporella'' * †'' Anisoporella'' * †'' Anthracoporella'' * †'' Archaeocladus'' * †'' Atractyliopsis'' * '' Batophora'' * †'' Beresella'' * '' Bornetella'' * †'' Chinianella'' * '' Chloroclados'' * †'' Clavapora'' * †'' Clavaporella'' * '' Connexia'' * '' Cylindroporella'' * '' Cymopolia'' * '' Dasycladus'' * '' Dissocladella'' * †'' Dvinella'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintained. Therefore, mitosis is also known as equational division. In general, mitosis is preceded by S phase of interphase (during which DNA replication occurs) and is often followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis altogether define the mitotic (M) phase of an animal cell cycle—the division of the mother cell into two daughter cells genetically identical to each other. The process of mitosis is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are preprophase (specific to plant cells), propha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carnets De Géologie
''Carnets Geol.'' (previously ''Carnets de Géologie'' or ''Carnets de Géologie - Notebooks on Geology'') is an electronic journal that publishes in the field of geosciences, and particularly paleontology, stratigraphy, and sedimentology. The open-access journal is one of the founding members of the OA portal Geoscience e-Journals. Since 2007, it is published by the eponymic Association Carnets de Géologie at the University of Western Brittany in Brest, France. Description ''Carnets Geol.'' publishes peer-reviewed contributions (memoirs, articles, and letters) on an irregular basis, that is each new paper is released online as soon as possible after the editorial office received the latest reviewed and corrected version from the author(s). These contributions are written either in English, French, or both languages, but articles in Spanish, German, or Italian will also appear. All include titles, abstracts, and keywords in both English and French. In addition to the journal is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The main components of the cytoplasm are cytosol (a gel-like substance), the organelles (the cell's internal sub-structures), and various cytoplasmic inclusions. The cytoplasm is about 80% water and is usually colorless. The submicroscopic ground cell substance or cytoplasmic matrix which remains after exclusion of the cell organelles and particles is groundplasm. It is the hyaloplasm of light microscopy, a highly complex, polyphasic system in which all resolvable cytoplasmic elements are suspended, including the larger organelles such as the ribosomes, mitochondria, the plant plastids, lipid droplets, and vacuoles. Most cellular activities take place within the cytoplasm, such as many metabolic pathways including glycolysis, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanometer
330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re, -er, American spelling) is a units of measurement, unit of length in the International System of Units (SI), equal to one billionth (short scale) of a metre () and to 1000 picometres. One nanometre can be expressed in scientific notation as , and as metres. History The nanometre was formerly known as the millimicrometre – or, more commonly, the millimicron for short – since it is of a micron (micrometre), and was often denoted by the symbol mμ or (more rarely and confusingly, since it logically should refer to a ''millionth'' of a micron) as μμ. Etymology The name combines the SI prefix ''nano-'' (from the Ancient Greek , ', "dwarf") with the parent unit name ''metre'' (from Greek , ', "unit of measurement"). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gametangia
A gametangium (plural: gametangia) is an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis. Types of gametangia Depending on the type of gamete produced in a gametangium, several types can be distinguished. Female Female gametangia are most commonly called archegonia. They produce egg cells and are the sites for fertilization. Archegonia are common in algae and primitive plants as well as gymnosperms. In flowering plants, they are replaced by the embryo sac inside the ovule. Male The male gametangia are most commonly called antheridia. They produce sperm cells that they release for fertilization. Antheridia producing non-motile sperm (spermatia) are called spermatangia. Some antheridia do not release their sperm. For example, the oomycete antheridium is a syn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
