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Xenophyophora
Xenophyophorea is a clade of foraminiferans. Xenophyophores are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of . They are a kind of foraminiferan that extract minerals from their surroundings and use them to form an exoskeleton known as a test. They were first described by Henry Bowman Brady in 1883. They are abundant on abyssal plains, and in some regions are the dominant species. Fifteen genera and 75 species have been described, varying widely in size. The largest, ''Syringammina fragilissima'', is among the largest known coenocytes, reaching up to in diameter. Naming and classification The name Xenophyophora means "bearer of foreign bodies", from the Greek. This refers to the sediments, called xenophyae, which are cemented together to construct their tests. In 1883, Henry Bowman Brady classified them as primitive Foraminifera. Later they were placed within the sponges. In the beginning of the 20th century they were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Franz Eilhard Schulze
Franz Eilhard Schulze (22 March 1840 – 2 November 1921) was a German anatomist and zoologist born in Eldena, near Greifswald. Biography He studied at the Universities of Bonn and Rostock. In 1863, he received his doctorate from Rostock, where he subsequently became a lecturer of anatomy (1864) and an associate professor of comparative anatomy (1865). In 1871 he established the zoological institute at the University of Rostock.See entry oFranz Eilhard Schulzein Catalogus Professorum Rostochiensium Later on, he served as a professor at the Universities of Graz and Berlin. In 1872, he took part in the "Pomerania" expedition to the North Sea. For several years during the 1890s, he was president of the German Zoological Society (''Deutsche Zoologische Gesellschaft''). He made contributions in his studies on the anatomy and developmental history of invertebrates, in particular, his research and publications in regards to sea-sponges. He was especially interested in a class of sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coenocyte
A coenocyte () is a multinucleate cell which can result from multiple nuclear divisions without their accompanying cytokinesis, in contrast to a syncytium, which results from cellular aggregation followed by dissolution of the cell membranes inside the mass. The word syncytium in animal embryology is used to refer to the coenocytic blastoderm of invertebrates. A coenocytic colony is referred to as a coenobium (: coenobia), and most coenobia are composed of a distinct number of cells, often as a multiple of two (4, 8, etc.). Research suggests that coenobium formation may be a defense against grazing in some species. Physiological examples Protists Diplomonads, like ''Giardia'', have two nuclei. Ciliates have cells that contain two nuclei: a macronucleus and a micronucleus. The schizont of apicomplexan parasites is a form of a coenocyte (i.e. a plasmodium in the general sense) as well as the plasmodia of microsporidian (Fungi) and myxosporidian (Metazoa) parasites. The tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expl2234 - Flickr - NOAA Photo Library
C mathematical operations are a group of functions in the standard library of the C programming language implementing basic mathematical functions. Different C standards provide different, albeit backwards-compatible, sets of functions. Most of these functions are also available in the C++ standard library, though in different headers (the C headers are included as well, but only as a deprecated compatibility feature). Overview of functions Most of the mathematical functions, which use floating-point numbers, are defined in ( header in C++). The functions that operate on integers, such as abs, labs, div, and ldiv, are instead defined in the header ( header in C++). Any functions that operate on angles use radians as the unit of angle. Not all of these functions are available in the C89 version of the standard. For those that are, the functions accept only type double for the floating-point arguments, leading to expensive type conversions in code that otherwise used single- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homoplasy
Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize the similarity of features that can be parsimoniously explained by common ancestry. Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift. Most often, homoplasy is viewed as a similarity in morphological characters. However, homoplasy may also appear in other character types, such as similarity in the genetic sequence, life cycle types or even behavioral traits. Etymology The term homoplasy was first used by Ray Lankester in 1870. The corresponding adjective is either ''homoplasic'' or ''homoplastic''. It is derived from the two Ancient Greek words (), meaning "similar, alike, the same", and (), meaning "to shape, to mold". Parallelism and convergence Parallel and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy. The recurrent evolution of flight is a classic example, as flying insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are ''analogous'', whereas '' homologous'' structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution, where related species evolve different traits. Convergent evolution is similar to parallel evol ... [...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] |
Syringammina Fragilissima
''Syringammina'' is a xenophyophore found off the coast of Ireland, near Rockall. It is one of the largest single-celled organisms known, at up to across. It was first described in 1882 by the oceanographer John Murray, after being discovered on an expedition in the ship ''Triton'' which dredged the deep ocean bed off the west coast of Scotland in an effort to find organisms new to science. It was the first xenophyophore to be described and at first its relationship with other organisms was a mystery, but it is now considered to be a member of the Foraminifera. The organism appears as an agglomeration of sediment a few centimetres across, a sandy ball that easily crumbles when removed from the seabed. It consists of a single cell which expands to form hundreds of hollow branched and interconnecting tubes; these secrete an organic cement to which particles of sediment and sand adhere, forming a crusty structure called the ''test''. As the test grows, the cell withdraws from pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SSU RRNA
Small subunit ribosomal ribonucleic acid (SSU rRNA) is the smaller of the two major RNA components of the ribosome. Associated with a number of ribosomal proteins, the SSU rRNA forms the small subunit of the ribosome. It is encoded by SSU- rDNA. Characteristics Use in phylogenetics SSU rRNA sequences are widely used for determining evolutionary relationships among organisms, since they are of ancient origin and are found in all known forms of life. See also *LSU rRNA Large subunit ribosomal ribonucleic acid (LSU rRNA) is the largest of the two major RNA components of the ribosome Ribosomes () are molecular machine, macromolecular machines, found within all cell (biology), cells, that perform Translation (b ...: the large subunit ribosomal ribonucleic acid. References {{Ribosome subunits Ribosomal RNA Protein biosynthesis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancestor excluding land plants, animals, and fungi. Protists were historically regarded as a separate taxonomic kingdom known as Protista or Protoctista. With the advent of phylogenetic analysis and electron microscopy studies, the use of Protista as a formal taxon was gradually abandoned. In modern classifications, protists are spread across several eukaryotic clades called supergroups, such as Archaeplastida ( photoautotrophs that includes land plants), SAR, Obazoa (which includes fungi and animals), Amoebozoa and " Excavata". Protists represent an extremely large genetic and ecological diversity in all environments, including extreme habitats. Their diversity, larger than for all other eukaryotes, has only been discovered in rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and are one of the most ancient members of macrobenthos, with many historical species being important reef-building organisms. Sponges are multicellular organisms consisting of jelly-like mesohyl sandwiched between two thin layers of cells, and usually have tube-like bodies full of pores and channels that allow water to circulate through them. They have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. They do not have complex nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes, usually via flagella movements of the so-called "collar cells". S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
