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Ahnfeltia Plicata
''Ahnfeltia plicata'', the landlady's wig, is a species of red alga in the family Ahnfeltiaceae. It grows in northern parts of the Atlantic Ocean. Description The landlady's wig forms tufted perennial plants with wiry fronds, branching from a discoid holdfast. The cylindrical fronds branch and are terete, they branch irregularly in a dichotomous manner. Each plant is about tall and wide. The holdfast is up to wide and composed of a thin layer encrusting the rock substrate. The frond's reddish-black colour results from the red pigments phycoerythrin and phycocyanin. Their colour is so intense that it masks the presence of other pigments, chlorophyll ''a'' and beta-Carotene. Some unique xanthophylls are also present in this seaweed. The landlady's wig could be confused with ''Cordylecladia erecta'' but that species is less common and is thicker with more rigid, regularly branched fronds. Distribution and habitat The landlady's wig is found on either side of the north Atlan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Hudson (botanist)
William Hudson FRS (1730 in Kendal – 23 May 1793) was a British botanist and apothecary based in London. His main work was ''Flora Anglica'', published in 1762. He was elected a fellow of the Royal Society in 1761. Life and work Hudson was born between 1730 and 1732 at the White Lion Inn, Kendal, which was kept by his father. He was educated at Kendal grammar school, Hudson was subsequently apprenticed to an apothecary in London. He obtained the prize for botany given by the Apothecaries' Company which was a copy of Ray's ''Synopsis''. However, he also paid attention to mollusca and insects and in Pennant's '' British Zoology'' he is mentioned as the discoverer of '' Trochus terrestris''. From 1757 to 1768 Hudson was resident sub-librarian of the British Museum, and his studies in the Sloane herbarium enabled him to adapt the Linnean nomenclature to the plants described by Ray far more accurately than did John Hill in his ''Flora Britannica'' of 1760. In 1761 Hudson w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dichotomy
A dichotomy is a partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be * jointly exhaustive: everything must belong to one part or the other, and * mutually exclusive: nothing can belong simultaneously to both parts. If there is a concept A, and it is split into parts B and not-B, then the parts form a dichotomy: they are mutually exclusive, since no part of B is contained in not-B and vice versa, and they are jointly exhaustive, since they cover all of A, and together again give A. Such a partition is also frequently called a bipartition. The two parts thus formed are complements. In logic, the partitions are opposites if there exists a proposition such that it holds over one and not the other. Treating continuous variables or multi categorical variables as binary variables is called dichotomization. The discretization error inherent in dichotomization is temporarily ignored for modeling purposes. Etymology The term '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gametangium
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 syncytium w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sorus
A sorus (pl. sori) is a cluster of sporangia (structures producing and containing spores) in ferns and fungi. A coenosorus (plural coenosori) is a compound sorus composed of multiple, fused sori. Etymology This New Latin word is from Ancient Greek σωρός (''sōrós'' 'stack, pile, heap'). Structure In lichens and other fungi, the sorus is surrounded by an external layer. In some red algae, it may take the form of depression into the thallus. In ferns, the sori form a yellowish or brownish mass on the edge or underside of a fertile frond. In some species, they are protected during development by a scale or film of tissue called the indusium, which forms an umbrella-like cover. Lifecycle significance Sori occur on the sporophyte generation, the sporangia within producing haploid meiospores. As the sporangia mature, the indusium shrivels so that spore release is unimpeded. The sporangia then burst and release the spores. As an aid to identification The shape, arrangemen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gametangium
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 syncytium w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holdfast (biology)
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. Holdfasts vary in shape and form depending on both the species and the substrate type. The holdfasts of organisms that live in muddy substrates often have complex tangles of root-like growths. These projections are called haptera and similar structures of the same name are found on lichens. The holdfasts of organisms that live in sandy substrates are bulb-like and very flexible, such as those of sea pens, thus permitting the organism to pull the entire body into the substrate when the holdfast is contracted. The holdfasts of organisms that live on smooth surfaces (such as the surface of a boulder) have flattened bases which adhere to the surface. The organism derives no nutrition from this intimate contact with the substrate, as the process of liberating nutrients from the substrate requires ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tide Pool
A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pool habitats are home to especially adaptable animals that have engaged the attention of naturalists and marine biologists, as well as philosophical essayists: John Steinbeck wrote in ''The Log from the Sea of Cortez'', "It is advisable to look from the tide pool to the stars and then back to the tide pool." Zones from shallow to deep The rocky shoreline exhibits zonation as a feature of the shoreline. Tidal movements of water creates zonation patterns along rocky shores from high to low-tide. The area above the high-tide mark is the supralittoral zone which is virtually a terrestrial environment. The area around the high-tide mark is known as the intertidal fringe. Between the high and low-tide marks is the intertidal or littoral zone. Below the low-tide mark is the sublittoral or subtida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cordylecladia Erecta
''Cordylecladia erecta'' is a species of red algae in the family Rhodymeniaceae. It is found in the north east Atlantic Ocean and the Mediterranean Sea and is the type species of the genus. Description ''Cordylecladia erecta'' grows in small tufts from a disc-like, rhizoidal, crustose base attached to rock but often hidden beneath the sand. It has tough reddish-brown cylindrical fronds that grow to . These are solid, either unbranched or sparsely branched dichotomously and taper to points. The reproductive structures are only visible in winter and appear as enlarged, spindle-shaped areas near the ends of the fronds. This seaweed could be confused with '' Ahnfeltia plicata'' but that species is more bushy with wiry fronds that branch irregularly and are only in diameter. Distribution and habitat ''Cordylecladia erecta'' occurs in the eastern Atlantic Ocean and the Mediterranean Sea. Its range extends from the Shetland Islands southwards but in the British Isles it is mostly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xanthophyll
Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek (, "yellow") and (, "leaf"), due to their formation of the yellow band seen in early chromatography of leaf pigments. Molecular structure As both are carotenoids, xanthophylls and carotenes are similar in structure, but xanthophylls contain oxygen atoms while carotenes are ''purely hydrocarbons'', which do not contain oxygen. Their content of oxygen causes xanthophylls to be more polar (in molecular structure) than carotenes, and causes their separation from carotenes in many types of chromatography. (Carotenes are usually more orange in color than xanthophylls.) Xanthophylls present their oxygen either as hydroxyl groups and/or as hydrogen atoms substituted by oxygen atoms when acting as a bridge to form epoxides. Occurrence Like other carotenoids, xanth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phycocyanin
Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble, so they cannot exist within the membrane like carotenoids can. Instead, phycobiliproteins aggregate to form clusters that adhere to the membrane called phycobilisomes. Phycocyanin is a characteristic light blue color, absorbing orange and red light, particularly near 620 nm (depending on which specific type it is), and emits fluorescence at about 650 nm (also depending on which type it is). Allophycocyanin absorbs and emits at longer wavelengths than phycocyanin C or phycocyanin R. Phycocyanins are found in cyanobacteria (also called blue-green algae). Phycobiliproteins have fluorescent properties that are used in immunoassay kits. Phycocyanin is from the Greek '' phyco'' meaning “algae” and ''cyanin'' is from the English word “cyan", which conven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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