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Raft Numbered ISO R 1146
A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barrels, or inflated air chambers (such as pontoons), and are typically not propelled by an engine. Rafts are an ancient mode of transport; naturally-occurring rafts such as entwined vegetation and pieces of wood have been used to traverse water since the dawn of humanity. Human-made rafts Traditional or primitive rafts were constructed of wood, bamboo or reeds; early buoyed or float rafts use inflated animal skins or sealed clay pots which are lashed together. Modern float rafts may also use pontoons, drums, or extruded polystyrene blocks. Depending on its use and size, it may have a superstructure, masts, or rudders. Timber rafting is used by the logging industry for the transportation of logs, by tying them together into rafts and drifti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Biology
Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and distribution of life. Central to biology are five fundamental themes: the cell (biology), cell as the basic unit of life, genes and heredity as the basis of inheritance, evolution as the driver of biological diversity, energy transformation for sustaining life processes, and the maintenance of internal stability (homeostasis). Biology examines life across multiple biological organisation, levels of organization, from molecules and cells to organisms, populations, and ecosystems. Subdisciplines include molecular biology, physiology, ecology, evolutionary biology, developmental biology, and systematics, among others. Each of these fields applies a range of methods to investigate biological phenomena, including scientific method, observation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Reptile
Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocephalia. About 12,000 living species of reptiles are listed in the Reptile Database. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology. Reptiles have been subject to several conflicting Taxonomy, taxonomic definitions. In Linnaean taxonomy, reptiles are gathered together under the Class (biology), class Reptilia ( ), which corresponds to common usage. Modern Cladistics, cladistic taxonomy regards that group as Paraphyly, paraphyletic, since Genetics, genetic and Paleontology, paleontological evidence has determined that birds (class Aves), as members of Dinosauria, are more closely related to living crocodilians than to other reptiles, and are thus nested among re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Amphibia
Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods, but excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds and mammals). All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs and toads), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems (such as riparian woodland, fossorial and even arboreal habitats). Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this. Young amphibians generally undergo metamorphosis from an aquatic larval form with gills to an air-breathi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Oceanic Dispersal
Oceanic dispersal is a type of biological dispersal that occurs when Terrestrial animal, terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between islands, as opposed to a single journey directly to the destination. Often this occurs via large rafts of floating vegetation such as are sometimes seen floating down major rivers in the tropics and washing out to sea, occasionally with animals trapped on them. Dispersal via such a raft is sometimes referred to as a rafting event. Colonization of land masses by plants can also occur via long-distance oceanic dispersal of floating seeds. History Rafting has played an important role in the colonization of isolated land masses by mammals. Prominent examples include Madagascar, which has been isolated for ~120 million years (Year#SI prefix multipliers, Ma), and South America, which was isolated for much of the Cenozoic. Both lan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Decomposition
Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. Decomposition can be a gradual process for organisms that have extended periods of dormancy. One can differentiate ''abiotic'' decomposition from ''biotic'' decomposition ( biodegradation); the former means "the degradation of a substance by chemical or physical processes", e.g., hydrolysis; the latter means "the metabolic breakdown of materials into simpler components by living organisms", typically by microorganisms. Animals, such as earthworms, also help decompose the organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Wave
In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a travelling wave; by contrast, a pair of superposition principle, superimposed periodic waves traveling in opposite directions makes a ''standing wave''. In a standing wave, the amplitude of vibration has nulls at some positions where the wave amplitude appears smaller or even zero. There are two types of waves that are most commonly studied in classical physics: mechanical waves and electromagnetic waves. In a mechanical wave, Stress (mechanics), stress and Strain (mechanics), strain fields oscillate about a mechanical equilibrium. A mechanical wave is a local deformation (physics), deformation (strain) in some physical medium that propa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus, the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the Displacement (fluid), displaced fluid. For this reason, an object with average density greater than the surrounding fluid tends to sink because its weight is greater than the weight of the fluid it displaces. If the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Flotsam And Jetsam
In maritime law, flotsam'','' jetsam'','' lagan'','' and derelict are terms for various types of property lost or abandoned at sea. The words have specific nautical meanings, with legal consequences in the law of admiralty and marine salvage. A shipwreck is defined as the remains of a ship that has been wrecked, whether it has sunk or is floating on the surface of the water. Overview A wreck is categorized as property belonging to no apparent owner that either sinks to the seabed or floats on the surface of the water, whether it be intentionally cast overboard or as the result of an accident. The term encompasses the hull of the vessel and its fixtures as well as any other form of object on board, such as cargo and stores, and personal effects of the crew and passengers. This also encompasses the narrower definition of salvage, that is, property that has been recovered from a wreckage, or the recovery of the ship itself. There are a number of factors that contribute to the for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. In its most general sense, the word ''earthquake'' is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear weapons testing. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can be used for any given locale to find the predicted times and amplitude (or " tidal range"). The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see '' Timing''). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Other locations have a diurnal tide—one high and low tide each day. A "mixed tide"—two uneven magnitude tides a day—is a third regular category. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tsunami
A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, landslides, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give the false impression of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
