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Aquatic Locomotion
Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish, molluscs, amphibians, reptiles, birds, and mammals. Evolution of swimming Swimming evolved a number of times in unrelated lineages. Supposed jellyfish fossils occur in the Ediacaran, but the first free-swimming animals appear in the Early to Middle Cambrian. These are mostly related to the arthropods, and include the Anomalocaridids, which swam by means of lateral lobes in a fashion reminiscent of today's cuttlefish. Cephalopods joined the ranks of the nekton in the late Cambrian, and chordates were probably swimming from the Early Cambrian. Many terrestrial animals retain some capacity to swim, however some have returned to the water and developed the capacities for aquatic locomotion. Most apes (including humans), however, lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diving Bird
Diving birds are birds which plunge into the water to catch fish or other prey. Such birds may enter the water from flight, such as pelicans, gannets and tropicbirds; or they may dive from the surface of the water, such as the diving ducks, cormorants and penguins. It is theorized that they evolved from birds already adapted for swimming that were equipped with such adaptations as lobed or webbed feet for propulsion. Foot-propelled diving birds Some diving birds, for example the extinct Hesperornithes of the Cretaceous Period, propelled themselves with their feet. They were large, streamlined, and flightless birds with teeth for grasping slippery prey. Today, cormorants (family Phalacrocoracidae), loons ( Gaviidae), and grebes ( Podicipedidae) are the major groups of foot-propelled diving birds. Wing-propelled diving birds Other diving birds are wing-propelled, most notably the penguins (Sphenisciformes), dippers (''Cinclus'') and auks (Alcidae). Plunge-diving birds Plunge- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuttlefish
Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of buoyancy. Cuttlefish have large, W-shaped pupils, eight arms, and two tentacles furnished with denticulated suckers, with which they secure their prey. They generally range in size from , with the largest species, the giant cuttlefish (''Sepia apama''), reaching in mantle length and over in mass. Cuttlefish eat small molluscs, crabs, shrimp, fish, octopus, worms, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds, and other cuttlefish. The typical life expectancy of a cuttlefish is about 1–2 years. Studies are said to indicate cuttlefish to be among the most intelligent invertebrates. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of ''Haloquadratum walsbyi''. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Motility
Bacterial motility is the ability of bacteria to move independently using metabolic energy. Most motility mechanisms which evolved among bacteria also evolved in parallel among the archaea. Most rod-shaped bacteria can move using their own power, which allows colonization of new environments and discovery of new resources for survival. Bacterial movement depends not only on the characteristics of the medium, but also on the use of different appendages to propel. Swarming and swimming movements are both powered by rotating flagella. Whereas swarming is a multicellular 2D movement over a surface and requires the presence of surfactants, swimming is movement of individual cells in liquid environments. Other types of movement occurring on solid surfaces include twitching, gliding and sliding, which are all independent of flagella. Twitching depends on the extension, attachment to a surface, and retraction of type IV pili which pull the cell forwards in a manner similar to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in older texts. The informal synonym ''microbe'' () comes from μικρός, mikrós, "small" and βίος, bíos, "life". is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from ancient times, such as in Jain scriptures from sixth century BC India. The scientific study of microorganisms began with their observation under the microscope in the 1670s by Anton van Leeuwenhoek. In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In the 1880s, Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera, diphtheria, and anthrax. Because mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microswimmer
A microswimmer is a microscopic object with the ability to move in a fluid environment. Natural microswimmers are found everywhere in the natural world as biological microorganisms, such as bacteria, archaea, protists, sperm and microanimals. Since the turn of the millennium there has been increasing interest in manufacturing synthetic and biohybrid microswimmers. Although only two decades have passed since their emergence, they have already shown promise for various biomedical and environmental applications. Given the recent nature of the field, there is yet no consensus in the literature for the nomenclature of the microscopic objects this article refers to as "microswimmers". Among the many alternative names such objects are given in the literature, microswimmers, micro/nanorobots and micro/nanomotors are likely the most frequently encountered. Other common terms may be more descriptive, including information about the object shape, e.g., microtube or microhelix, its components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microswimmer
A microswimmer is a microscopic object with the ability to move in a fluid environment. Natural microswimmers are found everywhere in the natural world as biological microorganisms, such as bacteria, archaea, protists, sperm and microanimals. Since the turn of the millennium there has been increasing interest in manufacturing synthetic and biohybrid microswimmers. Although only two decades have passed since their emergence, they have already shown promise for various biomedical and environmental applications. Given the recent nature of the field, there is yet no consensus in the literature for the nomenclature of the microscopic objects this article refers to as "microswimmers". Among the many alternative names such objects are given in the literature, microswimmers, micro/nanorobots and micro/nanomotors are likely the most frequently encountered. Other common terms may be more descriptive, including information about the object shape, e.g., microtube or microhelix, its components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doggy Paddle
The dog paddle or doggy paddle is a simple swimming style. It is characterized by the swimmer lying on their chest and moving their hands and legs alternately in a manner reminiscent of how dogs and other quadrupedal mammals swim. It is effectively a "trot" in water, instead of land. It was the first swimming stroke used by ancient humans, believed to have been learned by observing animals swim. Prehistoric cave paintings in Egypt show figures doing what appears to be the dog paddle. It is often the first swimming stroke used by young children when they are learning to swim. The dog paddle has also been taught as a military swimming stroke when a silent stroke is needed - since neither arms or legs break the surface. See also * List of swimming styles * Human swimming * Front crawl * Breaststroke Breaststroke is a swimming style in which the swimmer is on their chest and the torso does not rotate. It is the most popular recreational style due to the swimmer's head bein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Last Common Ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The term is also used in reference to the ancestry of groups of genes (haplotypes) rather than organisms. The MRCA of a set of individuals can sometimes be determined by referring to an established pedigree. However, in general, it is impossible to identify the exact MRCA of a large set of individuals, but an estimate of the time at which the MRCA lived can often be given. Such ''time to most recent common ancestor'' (''TMRCA'') estimates can be given based on DNA test results and established mutation rates as practiced in genetic genealogy, or by reference to a non-genetic, mathematical model or computer simulation. In organisms using sexual reproduction, the ''matrilineal MRCA'' and ''patrilineal MRCA'' are the MRCAs of a given population c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saci (Brazilian Folklore)
Saci ( ) is a character in Brazilian folklore. He is a one-legged black man, who smokes a pipe and wears a magical red cap that enables him to disappear and reappear wherever he wishes (usually in the middle of a Dirt devil). Considered an annoying prankster in most parts of Brazil, and a potentially dangerous and malicious creature in others, he nevertheless grants wishes to anyone who manages to trap him or steal his magic cap. However, his cap is often depicted as having a bad smell. Most people who claimed to have stolen this cap say they can never wash the smell away. The legend says that a person can trap a Saci inside a bottle when he is in the form of a dust devil. There are several variants of the myth, including: Saci-pererê (), black as coal; Saci-trique (), bi-racial and more benign; Saci-saçurá (), with red eyes. Powers, weaknesses, and habits An incorrigible prankster, the Saci causes no major harm, but there is no little harm that he won't do. He hides childre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of The Witwatersrand
The University of the Witwatersrand, Johannesburg (), is a multi-campus South African Public university, public research university situated in the northern areas of central Johannesburg. It is more commonly known as Wits University or Wits ( or ). The university has its roots in the mining industry, as do Johannesburg and the Witwatersrand in general. Founded in 1896 as the South African School of Mines in Kimberley, South Africa, Kimberley, it is the third oldest South African university in continuous operation. The university has an enrolment of 40,259 students as of 2018, of which approximately 20 percent live on campus in the university's 17 residences. 63 percent of the university's total enrolment is for Undergraduate education, undergraduate study, with 35 percent being Postgraduate education, postgraduate and the remaining 2 percent being Occasional Students. The 2017 Academic Ranking of World Universities (ARWU) places Wits University, with its overall score, as the h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Center For Academic Research And Training In Anthropogeny
The Center for Academic Research and Training in Anthropogeny (CARTA) is an Organized Research Unit (ORU) at the University of California, San Diego. Formally established in 2008, CARTA is a collaboration between faculty members of UCSD main campus, the UCSD School of Medicine, the Salk Institute for Biological Studies, and interested scientists at other institutions from around the world. CARTA was formed in order to promote transdisciplinary research into anthropogeny - the study of human origins - drawing on methods from a number of traditional disciplines spanning the humanities, social, biomedical, biological, computational & engineering and physical & chemical sciences. History of CARTA Before CARTA became an established and formal UCSD recognized Organized Research Unit, a multidisciplinary effort to study human origins had already been underway in the La Jolla area for over a decade, coordinated by the UCSD Project for Explaining the Origin of Humans (POH). The group i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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