1.
Pelagic zone
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Any water in a sea or lake that is neither close to the bottom nor near the shore can be said to be in the pelagic zone. The word pelagic is derived from Greek πέλαγος, meaning open sea, the pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes from the surface of the sea almost to the bottom. Conditions differ deeper in the water such that as pressure increases with depth. Depending on the depth, the column, rather like the Earths atmosphere. The pelagic zone occupies 1,330 million km3 with a depth of 3.68 km. Pelagic life decreases with increasing depth and it is affected by light intensity, pressure, temperature, salinity, the supply of dissolved oxygen and nutrients, and the submarine topography, which is called bathymetry. In deep water, the zone is sometimes called the open-ocean zone. In other contexts, coastal water not near the bottom is still said to be in the pelagic zone, the pelagic zone can be contrasted with the benthic and demersal zones at the bottom of the sea. The benthic zone is the region at the very bottom of the sea. It includes the sediment surface and some subsurface layers, Marine organisms living in this zone, such as clams and crabs, are called benthos. The demersal zone is just above the benthic zone and it can be significantly affected by the seabed and the life that lives there. Demersal fish are known as bottom feeders and groundfish. Depending on how deep the sea is, the zone can extend over up to five horizontal layers in the ocean. From the top down, these are, From the surface down to around 200 m This is the zone at the surface of the sea where enough light is available for photosynthesis. Nearly all primary production in the ocean occurs here, consequently, plants and animals are largely concentrated in this zone. Examples of organisms living in this zone are plankton, floating seaweed, jellyfish, tuna, many sharks, from 200 m down to around 1,000 m The name for this zone stems from Greek μέσον, meaning middle. Although some light penetrates this second layer it is insufficient for photosynthesis, at about 500 m the water also becomes depleted of oxygen. Organisms survive this environment by having more efficient gills or by minimizing movement, examples of animals that live here are swordfish, squid, Anarhichadidae or wolffish and some species of cuttlefish
2.
Photic zone
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The photic zone, euphotic zone, or sunlight or zone is the depth of the water in a lake or ocean that is exposed to such intensity of sunlight which designates compensation point, i. e. It extends from the surface down to a depth where light intensity falls to one percent of that at the surface, accordingly, its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes and it also varies with seasonal changes in turbidity. About 90% of all marine life lives in the photic zone, a small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges. The zone which extends from the base of the zone to about 200 metres is sometimes called the disphotic zone. While there is light, it is insufficient for photosynthesis. The euphotic zone together with the disphotic zone coincides with the epipelagic zone, the bottommost zone, below the euphotic zone, is called the aphotic zone. Most deep ocean waters belong to this zone, the transparency of the water, which determines the depth of the photic zone, is measured simply with a Secchi disk. It may also be measured with a photometer lowered into the water, electromagnetic absorption by water Epipelagic fish
3.
Bathyal zone
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The bathyal zone or bathypelagic – from Greek βαθύς, deep – is the part of the pelagic zone that extends from a depth of 1000 to 4000 meters below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below, the average temperature hovers at about 4 °C. Although larger by volume than the euphotic zone, the zone is less densely populated. Sunlight does not reach this zone, meaning primary production, if any, is almost nonexistent, there are no known plants because of the lack of sunlight necessary for photosynthesis. It is known as the zone because of this feature. Because of the lack of light, some species do not have eyes, however those possessing eyes in this include the viperfish. Many forms of live in the bathyal zone, such as squid, large whales. In the bathyal, some of the worlds largest whales feed, sponges, brachiopods, sea stars, and echinoids are also common in the bathyal zone. Animals in the zone are not threatened by predators that can see them. This zone is difficult for fish to live in, since it is hard to find nutrients. They have become very efficient, and many have slow metabolic rates to conserve energy. The fish are characterized by weak muscles, soft skin and slimy bodies, the adaptations of some of the fish that live there include small eyes and transparent skin. Except where the ocean is deep, the bathyal zone extends to the benthic zone on the ocean bed of that part of the continental slope that lies between 1000 and 4000 meters deep. The bathyal zone contains sharks, squid, octopuses, and many different species of fish, bathyal zones on the Mediterranean continental slope, An attempt. Research on marine benthos, 9th Iberian Symposium on Studies of Marine Benthos
4.
Abyssal zone
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The abyssal zone or abyssopelagic is a layer of the pelagic zone of the ocean. Abyss derives from the Greek word ἄβυσσος, meaning bottomless, at depths of 4,000 to 6,000 metres, this zone remains in perpetual darkness and never receives daylight. These regions are characterised by continuous cold and lack of nutrients. The abyssal zone has temperatures around 2 °C to 3 °C through the large majority of its mass. It is the part of the midnight zone which starts in the bathypelagic waters above. The area below the zone is the sparsely inhabited hadal zone. The zone above is the bathyal zone, the deep trenches or fissures that plunge down thousands of metres below the ocean floor are almost unexplored. Previously, only the bathyscaphe Trieste, the remote control submarine Kaiko, however, as of March 25,2012 one vehicle, the Deepsea Challenger was able to penetrate to a depth of 10,898.4 metres. Abyssal plain Deep sea Mariana Trench
5.
Hadal zone
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The hadal zone, also known as the hadopelagic zone and composed of trench zones, is the delineation for the deepest trenches in the ocean. The hadal zone is found from a depth to the bottom of the ocean of around 6,000 to 11,000 metres and exists in long, in total there are 33 trenches and 13 troughs around the world—46 individual hadal habitats in total. All the trenches together occupy an area less than one-quarter of one percent of the entire seafloor, the hadal zone has low population and low diversity of marine life. It is believed that most life at this depth is sustained by marine snow or the chemical reactions around thermal vents, the low nutrient level, extreme pressure and lack of sunlight create hostile living conditions in which few species are able to exist. As no sunlight reaches this layer of the ocean, deep sea creatures have reduced eyesight, the most common organisms include jellyfish, viperfish, tube worms and sea cucumbers. The hadal zone can reach far below 6,000 meters deep, at such depths the pressure in the hadal zone exceeds 1,100 standard atmospheres. In 1960, Jacques Piccard and Don Walsh reached the bottom of the Mariana Trench, the deepest known trench on Earth, james Cameron also reached the bottom in 2012 using the Deepsea Challenger. Abyssal plain Deep sea Alan Jamieson, The hadal zone - life in the deepest oceans, forscher filmen lebende Fische in Rekordtiefe from Spiegel 10/09/2008 about an expedition filming fish at a depth of more than 7,000 m
6.
Demersal zone
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The demersal zone is the part of the sea or ocean consisting of the part of the water column near to the seabed and the benthos. The demersal zone is just above the zone and forms a layer of the larger profundal zone. The distinction between species of fish and pelagic species is not always clear cut. Two types of fish inhabit the zone, those that are heavier than water and rest on the seabed. In many species of fish, neutral buoyancy is maintained by a swim bladder which can be expanded or contracted as the circumstances require. A disadvantage of this method is that adjustments need to be made constantly as the pressure varies when the fish swims higher and lower in the water column. An alternative buoyancy aid is the use of lipids, these are less dense water and squalene. In the velvet belly lanternshark, a species, 17% of the bodyweight is liver. Benthic rays and skates have smaller livers with lower concentrations of lipids, they are denser than water. Some fish have no buoyancy aids but use their pectoral fins which are so angled as to lift as they swim. The disadvantage of this is that, if they stop swimming, the fish sink, demersal fish have various feeding strategies, many feed on zooplankton or organisms or algae on the seabed, some of these feed on epifauna, while others specialise on infauna. Others are scavengers, eating the remains of plants or animals while still others are predators. Zooplankton are animals that drift with the current, but many have limited means of locomotion and have some control over the depths at which they drift. They use gas-filled sacs or accumulations of substances with low densities to provide buoyancy, where the adult, benthic organism is limited to life in a certain range of depths, their larvae need to optimise their chances of settling on a suitable substrate. Cuttlefish are able to adjust their buoyancy using their cuttlebones, lightweight rigid structures with cavities filled with gas and this enables them to swim at varying depths. Another invertebrate that feeds on the seabed and has swimming abilities is the nautilus, which stores gas in its chambers and adjusts its buoyancy by use of osmosis, pumping water in and out
7.
Benthic zone
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The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos, e. g. the benthic community, including crustaceans. The organisms generally live in relationship with the substrate bottom. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, the benthic region of the ocean begins at the shore line and extends downward along the surface of the continental shelf out to sea. The continental shelf is a gently sloping benthic region that extends away from the land mass, at the continental shelf edge, usually about 200 meters deep, the gradient greatly increases and is known as the continental slope. The continental slope drops down to the sea floor. The deep-sea floor is called the plain and is usually about 4,000 meters deep. The ocean floor is not all flat but has submarine ridges, for comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water-column up to the surface. For information on animals that live in the areas of the oceans see aphotic zone. Generally, these life forms that tolerate cool temperatures and low oxygen levels. Benthos are the organisms live in the benthic zone, and are different from those elsewhere in the water column. Many are adapted to live on the substrate, in their habitats they can be considered as dominant creatures, but they are often a source of prey for Carcharhinidae such as the lemon shark. Many organisms adapted to deep-water pressure cannot survive in the parts of the water column. The pressure difference can be very significant, because light does not penetrate very deep into ocean-water, the energy source for the benthic ecosystem is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain, most organisms in the zone are scavengers or detritivores. Some microorganisms use chemosynthesis to produce biomass, Benthic organisms can be divided into two categories based on whether they make their home on the ocean floor or an inch or two into the ocean floor. Those living on the surface of the floor are known as epifauna. Those who live burrowed into the floor are known as infauna
8.
Stratification (water)
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These layers are normally arranged according to density, with the least dense water masses sitting above the more dense layers. Water stratification also creates barriers to nutrient mixing between layers and this can affect the primary production in an area by limiting photosynthetic processes. When nutrients from the benthos cannot travel up into the photic zone, lower primary production also leads to lower net productivity in waters. Stratification may be upset by turbulence and this creates mixed layers of water. Forms of turbulence may include surface friction, upwelling and downwelling. Marshall et al. suggest that baroclinic eddies may be an important factor in maintaining stratification, canfield ocean Cline Lake stratification Meromictic
9.
Halocline
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In oceanography, a halocline is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity affects the density of seawater, it can play a role in its vertical stratification, increasing salinity by one kg/m3 results in an increase of seawater density of around 0.7 kg/m3. In the midlatitudes, an excess of evaporation over precipitation leads to surface waters being saltier than deep waters, in such regions, the vertical stratification is due to surface waters being warmer than deep waters and the halocline is destabilizing. Such regions may be prone to salt fingering, a process results in the preferential mixing of salinity. In these regions, the halocline is important in allowing for the formation of sea ice, haloclines are also found in fjords, and poorly mixed estuaries where fresh water is deposited at the ocean surface. In the plot, one can discern three layers, About 50 m of low salinity water swimming on top of the ocean, the temperature is -1.8 °C, which is very near to the freezing point. This layer blocks heat transfer from the warmer, deeper levels into the sea ice, about 150 m of steeply rising salinity and increasing temperature. The deep layer with nearly constant salinity and slowly decreasing temperature, a halocline can be easily created and observed in a drinking glass or other clear vessel. A halocline is most commonly confused with a thermocline - a thermocline is an area within a body of water that marks a change in temperature. Haloclines are common in water-filled caves near the ocean, less dense fresh water from the land forms a layer over salt water from the ocean. For underwater cave explorers, this can cause the illusion of air space in caverns. Passing through the halocline tends to stir up the layers, thermocline - A cline based on difference in water temperature, Chemocline - A cline based on difference in water chemistry, Pycnocline - A cline based on difference in water density. Hypersaline lake Isopycnal Thermohaline circulation Osmotic power
10.
Thermocline
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A thermocline is a thin but distinct layer in a large body of fluid in which temperature changes more rapidly with depth than it does in the layers above or below. In the ocean, the thermocline divides the upper mixed layer from the deep water below. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude and local conditions, such as tides. Most of the energy of sunlight is absorbed in the first few centimeters at the oceans surface. Below this mixed layer, the temperature remains relatively stable over day/night cycles, the temperature of the deep ocean drops gradually with depth. As saline water does not freeze until it reaches −2.3 °C the temperature well below the surface is not far from zero degrees. It is semi-permanent in the tropics, variable in temperate regions and shallow to nonexistent in the polar regions, a layer of sea ice will act as an insulation blanket. Technically, this stems from a discontinuity in the acoustic impedance of water created by the sudden change in density. It gives the water an appearance of wrinkled glass that is used to obscure bathroom windows and is caused by the altered refractive index of the cold or warm water column. These same schlieren can be observed when hot air rises off the tarmac at airports or desert roads and is the cause of mirages, thermoclines can also be observed in lakes. In colder climates, this leads to a phenomenon called stratification, during the summer, warm water, which is less dense, will sit on top of colder, denser, deeper water with a thermocline separating them. The warm layer is called the epilimnion and the layer is called the hypolimnion. Because the warm water is exposed to the sun during the day, as winter approaches, the temperature of the surface water will drop as nighttime cooling dominates heat transfer. This process is aided by wind or any process that agitates the water. This effect also occurs in Arctic and Antarctic waters, bringing water to the surface which and this enriching of surface nutrients may produce blooms of phytoplankton, making these areas productive. As the temperature continues to drop, the water on the surface may get cold enough to freeze, a new thermocline develops where the densest water sinks to the bottom, and the less dense water rises to the top. Once this new stratification establishes itself, it lasts until the water warms enough for the turnover, which occurs after the ice melts. During this transition, a bar may develop
11.
Thermohaline circulation
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Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
12.
Marine habitats
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The marine environment supplies many kinds of habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea, a habitat is an ecological or environmental area inhabited by one or more living species. Marine habitats can be divided into coastal and open ocean habitats, coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf. Most marine life is found in habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the ocean beyond the edge of the continental shelf. Alternatively, marine habitats can be divided into pelagic and demersal zones, pelagic habitats are found near the surface or in the open water column, away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean, an organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish. Similarly, a living in a demersal habitat is said to be a demersal organism. Pelagic habitats are shifting and ephemeral, depending on what ocean currents are doing. Marine habitats can be modified by their inhabitants, some marine organisms, like corals, kelp, mangroves and seagrasses, are ecosystem engineers which reshape the marine environment to the point where they create further habitat for other organisms. In contrast to terrestrial habitats, marine habitats are shifting and ephemeral, swimming organisms find areas by the edge of a continental shelf a good habitat, but only while upwellings bring nutrient rich water to the surface. Shellfish find habitat on sandy beaches, but storms, tides, the presence of seawater is common to all marine habitats. Beyond that many other things determine whether a marine area makes a good habitat, the ocean occupies 71 percent of the world surface, averaging nearly four kilometres in depth. There are five major oceans, of which the Pacific Ocean is nearly as large as the rest put together, coastlines fringe the land for nearly 380,000 kilometres. Marine habitats can be divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the water column, away from the bottom of the ocean. Demersal habitats are the habitats that are near or on the bottom of the ocean, an organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish. Similarly, a living in a demersal habitat is said to be a demersal organism
13.
Lake stratification
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Lake stratification is the separation of lakes into three layers, Epilimnion, the top of the lake. Metalimnion, the layer, which may change depth throughout the day. The thermal stratification of lakes refers to a change in the temperature at different depths in the lake, cold water is denser than warm water and the epilimnion generally consists of water that is not as dense as the water in the hypolimnion. However, the temperature of maximum density for freshwater is 4 °C, for example, in dimictic lakes the lake water turns over during the spring and the fall. This process occurs slowly in deeper water and as a result. If the stratification of water lasts for extended periods, the lake is meromictic, conversely, for most of the time, the relatively shallower meres are unstratified, that is, the mere is considered all epilimnion. Natural resource and environmental managers are often challenged by problems caused by lake, fish die-offs have been directly associated with thermal gradients, stagnation, and ice cover. Excessive growth of plankton may limit the use of lakes. With severe thermal stratification in a lake, the quality of drinking water also can be adversely affected, one commonly used tool to reduce the severity of these lake management problems is to eliminate or lessen thermal stratification through aeration. Many types of equipment have been used to thermally destratify lakes. Aeration has met some success, although it has rarely proved to be a panacea. Lake Stratification in Lake Lanier and its effects on the Chattahoochee River Lackey, a technique for eliminating thermal stratification in lakes. Water Resources Bulletin, Journal of the American Water Resources Association, response of physical and chemical parameters to eliminating thermal stratification in a reservoir. Water Resources Bulletin, Journal of the American Water Resources Association, http, //onlinelibrary. wiley. com/doi/10. 1111/j. 1752-1688.1972. tb05181. x/abstract Lackey, Robert T. and Donald W. Holmes. Evaluation of two methods of aeration to prevent winterkill, density Stratification, part of an educational website Water on the Web operated by the University of Minnesota, Duluth. Aquatic Science Stratification Hypoxia Freshwater ecosystems Water column Lake aeration Aquatic Science Hypoxia Freshwater ecosystems Water column
14.
Aquatic ecosystem
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An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on other and on their environment live in aquatic ecosystems. The two main types of ecosystems are marine ecosystems and freshwater ecosystems. Marine ecosystems cover approximately 71% of the Earths surface and contain approximately 97% of the planets water and they generate 32% of the worlds net primary production. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has a salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems, marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, the benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides, in this figure it is termed the littoral zone, other near-shore zones can include estuaries, salt marshes, coral reefs, lagoons and mangrove swamps. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web, classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Fishes caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations, environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources, marine pollution, climate change, and building on coastal areas. Freshwater ecosystems cover 0. 78% of the Earths surface and inhabit 0. 009% of its total water and they generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the known fish species. There are three types of freshwater ecosystems, Lentic, slow moving water, including pools, ponds. Lotic, faster moving water, for example streams and rivers, wetlands, areas where the soil is saturated or inundated for at least part of the time. Lake ecosystems can be divided into zones, one common system divides lakes into three zones. The first, the zone, is the shallow zone near the shore. This is where rooted wetland plants occur, the offshore is divided into two further zones, an open water zone and a deep water zone
15.
Wild fisheries
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A fishery is an area with an associated fish or aquatic population which is harvested for its commercial value. Fisheries can be marine or freshwater and they can also be wild or farmed. Wild fisheries are sometimes called capture fisheries, the aquatic life they support is not controlled in any meaningful way and needs to be captured or fished. Wild fisheries exist primarily in the oceans, and particularly around coasts and they also exist in lakes and rivers. Issues with wild fisheries are overfishing and pollution, significant wild fisheries have collapsed or are in danger of collapsing, due to overfishing and pollution. Overall, production from the wild fisheries has levelled out. As a contrast to wild fisheries, farmed fisheries can operate in sheltered waters, in rivers, lakes and ponds. Farmed fisheries are technological in nature, and revolve around developments in aquaculture, farmed fisheries are expanding, and Chinese aquaculture in particular is making many advances. Nevertheless, the majority of fish consumed by humans continues to be sourced from wild fisheries, as of the early 21st century, fish is humanitys only significant wild food source. This can be contrasted with 59.9 million tonnes produced in fish farms, worldwide, freshwater lakes have an area of 1.5 million square kilometres. Saline inland seas add another 1.0 million square kilometres, there are 28 freshwater lakes with an area greater than 5,000 square kilometres, totalling 1.18 million square kilometres or 79 percent of the total. Pollution is the introduction of contaminants into an environment, land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into the sea. Pollution from ships is also a problem, Marine debris is human-created waste that ends up floating in the sea. Oceanic debris tends to accumulate at the centre of gyres and coastlines, eighty percent of all known marine debris is plastic - a component that has been rapidly accumulating since the end of World War II. Discarded plastic bags, six rings and other forms of plastic waste which finish up in the ocean present dangers to wildlife. Aquatic life can be threatened through entanglement, suffocation, and ingestion, nurdles, also known as mermaids tears, are plastic pellets typically under five millimetres in diameter, and are a major contributor to marine debris. They are used as a raw material in manufacturing, and are thought to enter the natural environment after accidental spillages. Nurdles are also created through the weathering of larger plastic debris
16.
Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
17.
Sea level
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Mean sea level is an average level of the surface of one or more of Earths oceans from which heights such as elevations may be measured. A common and relatively straightforward mean sea-level standard is the midpoint between a low and mean high tide at a particular location. Sea levels can be affected by factors and are known to have varied greatly over geological time scales. The careful measurement of variations in MSL can offer insights into ongoing climate change, the term above sea level generally refers to above mean sea level. Precise determination of a sea level is a difficult problem because of the many factors that affect sea level. Sea level varies quite a lot on several scales of time and this is because the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity and so forth. The easiest way this may be calculated is by selecting a location and calculating the mean sea level at that point, for example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point. One measures the values of MSL in respect to the land, hence a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates. In the UK, the Ordnance Datum is the sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the datum was MSL at the Victoria Dock, in Hong Kong, mPD is a surveying term meaning metres above Principal Datum and refers to height of 1. 230m below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and it is used for a part of continental Europe and main part of Africa as official sea level. Elsewhere in Europe vertical elevation references are made to the Amsterdam Peil elevation, satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001, height above mean sea level is the elevation or altitude of an object, relative to the average sea level datum. It is also used in aviation, where some heights are recorded and reported with respect to sea level, and in the atmospheric sciences. An alternative is to base height measurements on an ellipsoid of the entire Earth, in aviation, the ellipsoid known as World Geodetic System 84 is increasingly used to define heights, however, differences up to 100 metres exist between this ellipsoid height and mean tidal height. The alternative is to use a vertical datum such as NAVD88. When referring to geographic features such as mountains on a topographic map, the elevation of a mountain denotes the highest point or summit and is typically illustrated as a small circle on a topographic map with the AMSL height shown in metres, feet or both. In the rare case that a location is below sea level, for one such case, see Amsterdam Airport Schiphol
18.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
19.
Water cycle
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The water cycle, also known as the hydrological cycle or the hydrologic cycle, describes the continuous movement of water on, above and below the surface of the Earth. In doing so, the water goes through different forms, liquid, solid, the water cycle involves the exchange of energy, which leads to temperature changes. For instance, when water evaporates, it takes up energy from its surroundings, when it condenses, it releases energy and warms the environment. The evaporative phase of the cycle purifies water which then replenishes the land with freshwater, the flow of liquid water and ice transports minerals across the globe. It is also involved in reshaping the geological features of the Earth, the water cycle is also essential for the maintenance of most life and ecosystems on the planet. The sun, which drives the cycle, heats water in oceans. Water evaporates as water vapor into the air, ice and snow can sublimate directly into water vapour. Evapotranspiration is water transpired from plants and evaporated from the soil, the water vapour molecule H 2O has less density compared to the major components of the atmosphere, nitrogen and oxygen, N2 andO2. Due to the significant difference in mass, water vapor in gas form gains height in open air as a result of buoyancy. However, as increases, air pressure decreases and the temperature drops. The lowered temperature causes water vapour to condense into a liquid water droplet which is heavier than the air. A huge concentration of these droplets over a space up in the atmosphere become visible as cloud. Fog is formed if the water vapour condenses near ground level, as a result of moist air, air currents move water vapour around the globe, cloud particles collide, grow, and fall out of the upper atmospheric layers as precipitation. Some precipitation falls as snow or hail, sleet, and can accumulate as ice caps and glaciers, most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, runoff and water emerging from the ground may be stored as freshwater in lakes. Not all runoff flows into rivers, much of it soaks into the ground as infiltration, some water infiltrates deep into the ground and replenishes aquifers, which can store freshwater for long periods of time. Some infiltration stays close to the surface and can seep back into surface-water bodies as groundwater discharge. Some groundwater finds openings in the surface and comes out as freshwater springs
20.
World War II
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World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945, although related conflicts began earlier. It involved the vast majority of the worlds countries—including all of the great powers—eventually forming two opposing alliances, the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. Marked by mass deaths of civilians, including the Holocaust and the bombing of industrial and population centres. These made World War II the deadliest conflict in human history, from late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. In December 1941, Japan attacked the United States and European colonies in the Pacific Ocean, and quickly conquered much of the Western Pacific. The Axis advance halted in 1942 when Japan lost the critical Battle of Midway, near Hawaii, in 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained all of its territorial losses and invaded Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in South Central China and Burma, while the Allies crippled the Japanese Navy, thus ended the war in Asia, cementing the total victory of the Allies. World War II altered the political alignment and social structure of the world, the United Nations was established to foster international co-operation and prevent future conflicts. The victorious great powers—the United States, the Soviet Union, China, the United Kingdom, the Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonisation of Asia, most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to end pre-war enmities, the start of the war in Europe is generally held to be 1 September 1939, beginning with the German invasion of Poland, Britain and France declared war on Germany two days later. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or even the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously and this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and the Soviet Union from May to September 1939, the exact date of the wars end is also not universally agreed upon. It was generally accepted at the time that the war ended with the armistice of 14 August 1945, rather than the formal surrender of Japan
21.
Anti-submarine warfare
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Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines. Successful anti-submarine warfare depends on a mix of sensor and weapon technology, training, sophisticated sonar equipment for first detecting, then classifying, locating and tracking the target submarine is a key element of ASW. To destroy submarines both the torpedo and mine are used, launched from air, surface and underwater platforms, other means of destruction have been used in the past but are now obsolete. ASW also involves protecting friendly ships, the first self-propelled torpedo was invented in 1863 and launched from surface craft. The first submarine with a torpedo was Nordenfelt I built in 1884-1885, in the Russo-Japanese War of 1904-5, the submarine was a significant threat. By the start of the First World War nearly 300 submarines were in service, some warships were fitted with an armoured belt as protection against torpedoes. There were, however, no means to detect submerged U-boats, the Royal Navy torpedo establishment, HMS Vernon, studied explosive grapnel sweeps, these sank four or five U-boats in the First World War. A similar approach featured a string of 70 lb charges on a cable, fired electrically. Also tried were dropping 18.5 lb hand-thrown guncotton bombs, the Lance Bomb was developed, also, this featured a 35–40 lb cone-shaped steel drum on a 5 ft shaft, intended to be thrown at a submarine. Firing Lyddite shells, or using trench mortars, was tried, use of nets to ensnare U-boats was also examined, as was a destroyer, HMS Starfish, fitted with a spar torpedo. Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the Type B and these were effective at a distance of around 20 ft. The best concept arose in a 1913 RN Torpedo School report, describing a device intended for countermining, at Admiral John Jellicoes request, the standard Mark II mine was fitted with a hydrostatic pistol preset for 45 ft firing, to be launched from a stern platform. Weighing 1,150 lb, and effective at 100 ft, the mine was a potential hazard to the dropping ship. During the First World War, submarines were a major menace and they operated in the Baltic, North Sea, Black Sea and Mediterranean as well as the North Atlantic. Previously they had limited to relatively calm and protected waters. The vessels used to them were a range of small, fast surface ships using guns. They mainly relied on the fact a submarine of the day was often on the surface for a range of reasons, the first approach to protect warships was chainlink nets strung from the sides of battleships, as defense against torpedoes. Nets were also deployed across the mouth of a harbour or naval base to stop submarines entering or to stop torpedoes of the Whitehead type fired against ships, British warships were fitted with a ram with which to sink submarines, and U-15 was thus sunk in August 1914
22.
Sonar
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Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name sonar, passive sonar is essentially listening for the sound made by vessels, active sonar is emitting pulses of sounds, Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of targets in the water. Acoustic location in air was used before the introduction of radar, Sonar may also be used in air for robot navigation, and SODAR is used for atmospheric investigations. The term sonar is used for the equipment used to generate. The acoustic frequencies used in sonar systems vary from low to extremely high. The study of sound is known as underwater acoustics or hydroacoustics. In the 19th century a bell was used as an ancillary to lighthouses to provide warning of hazards. The use of sound to locate underwater in the same way as bats use sound for aerial navigation seems to have been prompted by the Titanic disaster of 1912. S. Revenue Cutter Miami on the Grand Banks off Newfoundland Canada, in that test, Fessenden demonstrated depth sounding, underwater communications and echo ranging. The so-called Fessenden oscillator, at ca.500 Hz frequency, was unable to determine the bearing of the due to the 3 metre wavelength. The ten Montreal-built British H class submarines launched in 1915 were equipped with a Fessenden oscillator, during World War I the need to detect submarines prompted more research into the use of sound. Although piezoelectric and magnetostrictive transducers later superseded the electrostatic transducers they used, lightweight sound-sensitive plastic film and fibre optics have been used for hydrophones, while Terfenol-D and PMN have been developed for projectors. By 1918, both France and Britain had built prototype active systems, the British tested their ASDIC on HMS Antrim in 1920, and started production in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923, an anti-submarine school, HMS Osprey, and a training flotilla of four vessels were established on Portland in 1924. The US Sonar QB set arrived in 1931, by the outbreak of World War II, the Royal Navy had five sets for different surface ship classes, and others for submarines, incorporated into a complete anti-submarine attack system. The effectiveness of early ASDIC was hamstrung by the use of the charge as an anti-submarine weapon. This required a vessel to pass over a submerged contact before dropping charges over the stern. The hunter was effectively firing blind, during which time a commander could take evasive action
23.
Photosynthesis
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Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms activities. In most cases, oxygen is released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis, such organisms are called photoautotrophs, in plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, in the Calvin cycle, atmospheric carbon dioxide is incorporated into already existing organic carbon compounds, such as ribulose bisphosphate. Using the ATP and NADPH produced by the light-dependent reactions, the compounds are then reduced and removed to form further carbohydrates. Cyanobacteria appeared later, the oxygen they produced contributed directly to the oxygenation of the Earth. Today, the rate of energy capture by photosynthesis globally is approximately 130 terawatts. Photosynthetic organisms also convert around 100–115 thousand million tonnes of carbon into biomass per year. Photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide, however, not all organisms that use light as a source of energy carry out photosynthesis, photoheterotrophs use organic compounds, rather than carbon dioxide, as a source of carbon. In plants, algae, and cyanobacteria, photosynthesis releases oxygen and this is called oxygenic photosynthesis and is by far the most common type of photosynthesis used by living organisms. Although there are differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also varieties of anoxygenic photosynthesis, used mostly by certain types of bacteria. Carbon dioxide is converted into sugars in a process called carbon fixation, photosynthesis provides the energy in the form of free electrons that are used to split carbon from carbon dioxide that is then used to fix that carbon once again as carbohydrate. Carbon fixation is a redox reaction, so photosynthesis supplies the energy that drives both process. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the energy-storage molecules ATP, during the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide. Most organisms that utilize oxygenic photosynthesis use visible light for the light-dependent reactions, some organisms employ even more radical variants of photosynthesis. Some archea use a method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump and this produces a proton gradient more directly, which is then converted to chemical energy
24.
Herbivore
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A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding, horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter and this gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores intestines. Herbivore is the form of a modern Latin coinage, herbivora. Richard Owen employed the term in an 1854 work on fossil teeth. Herbivora is derived from the Latin herba meaning a small plant or herb, Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms feed on autotrophs in general are known as primary consumers. Herbivory usually refers to eating plants, fungi, bacteria and protists that feed on living plants are usually termed plant pathogens. Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants, there is however no single exclusive and definitive ecological classification of consumption patterns, each textbook has its own variations on the theme. Insects fed on the spores of early Devonian plants, and the Rhynie chert also provides evidence that organisms fed on plants using a pierce, during the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian,330.9 million years ago, further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period, Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores, while amphibians continued to feed on fish and insects, some reptiles began exploring two new food types, tetrapods and plants. The entire dinosaur order ornithischia was composed with herbivores dinosaurs, carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a set of adaptations was necessary for feeding on highly fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities, tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion, the evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores and this suggests that evolution and spread occurred simultaneously within various lineages
25.
Detritivore
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Detritivores, also known as detrivores, detritophages, detritus feeders, or detritus eaters, are heterotrophs that obtain nutrients by consuming detritus. There are many kinds of invertebrates, vertebrates and plants carry out coprophagy. By doing so, all these detritivores contribute to decomposition and the nutrient cycles, however, the terms detritivore and decomposer are often used interchangeably. Detritivores are an important aspect of many ecosystems and they can live on any soil with an organic component, including marine ecosystems, where they are termed interchangeably with bottom feeders. The eating of wood, whether alive or dead, is known as xylophagy, Τhe activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous. In food webs, detritivores generally play the roles of decomposers, detritivores are often eaten by consumers and therefore commonly play important roles as recyclers in ecosystem energy flow and biogeochemical cycles. Many detritivores live in woodland, though the term can be applied to certain bottom-feeders in wet environments. These organisms play a role in benthic ecosystems, forming essential food chains. Fungi, acting as decomposers, are important in todays terrestrial environment, by feeding on sediments directly to extract the organic component, some detritivores accidentally concentrate toxic pollutants. Decomposer Saprotrophic nutrition Nepenthes ampullaria Consumer-resource systems
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Carnivore
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Animals that depend solely on animal flesh for their nutrient requirements are called obligate carnivores while those that also consume non-animal food are called facultative carnivores. A carnivore that sits at the top of the chain is termed an apex predator. Plants that capture and digest insects are called carnivorous plants, similarly, fungi that capture microscopic animals are often called carnivorous fungi. The word carnivore sometimes refers to the mammalian order Carnivora, while many Carnivora meet the definition of being meat eaters, not all do, and even fewer are true obligate carnivores. In addition, there are plenty of species that are not members of Carnivora. Outside the animal kingdom, there are several genera containing carnivorous plants, the former are predominantly insectivores, while the latter prey mostly on microscopic invertebrates, such as nematodes, amoebae and springtails. Carnivores are sometimes characterized by the type of prey that they consume, for example, animals that eat insects and similar invertebrates primarily or exclusively are called insectivores, while those that eat fish primarily or exclusively are called piscivores. The first tetrapods, or land-dwelling vertebrates, were piscivorous amphibians known as labyrinthodonts and they gave rise to insectivorous vertebrates and, later, to predators of other tetrapods. Carnivores may alternatively be classified according to the percentage of meat in their diet, obligate carnivores or true carnivores depend on the nutrients found only in animal flesh for their survival. For instance, felids including the cat are obligate carnivores requiring a diet of primarily animal flesh. Characteristics commonly associated with carnivores include organs for capturing and disarticulating prey, in truth, these assumptions may be misleading, as some carnivores do not hunt and are scavengers. Thus they do not have the associated with hunting carnivores. Carnivores have comparatively short digestive systems, as they are not required to break down tough cellulose found in plants, many animals that hunt other animals have evolved eyes that face forward, thus making depth perception possible. This is almost universal among mammalian predators, other predators, like crocodiles, as well as most reptiles and amphibians, have sideways facing eyes and hunt by ambush rather than pursuit. The first vertebrate carnivores were fish, and then amphibians that moved on to land, early tetrapods were large amphibious piscivores. Some scientists assert that Dimetrodon was the first terrestrial vertebrate to develop the curved, serrated teeth that enable a predator to eat prey much larger than itself. While amphibians continued to feed on fish and later insects, reptiles began exploring two new types, tetrapods, and later, plants. Carnivory was a transition from insectivory for medium and large tetrapods
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Algae
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Algae is an informal term for a large, diverse group of photosynthetic organisms which are not necessarily closely related, and is thus polyphyletic. Included organisms range from unicellular genera, such as Chlorella and the diatoms, to forms, such as the giant kelp. Most are aquatic and autotrophic and lack many of the cell and tissue types, such as stomata, xylem, and phloem. No definition of algae is generally accepted, one definition is that algae have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells. Some authors exclude all prokaryotes thus do not consider cyanobacteria as algae, Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria, diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction. Algae lack the various structures that characterize land plants, such as the phyllids of bryophytes, rhizoids in nonvascular plants, and the roots, leaves, and other organs found in tracheophytes. Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some other heterotrophic organisms, such as the apicomplexans, are derived from cells whose ancestors possessed plastids. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago, the singular alga is the Latin word for seaweed and retains that meaning in English. Although some speculate that it is related to Latin algēre, be cold, a more likely source is alliga, binding, entwining. The Ancient Greek word for seaweed was φῦκος, which could mean either the seaweed or a red dye derived from it, the Latinization, fūcus, meant primarily the cosmetic rouge. It could be any color, black, red, green, accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name Fucus appears in a number of taxa, most algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and presumably represent reduced endosymbiotic cyanobacteria, however, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three groups of algae. Their lineage relationships are shown in the figure in the upper right, many of these groups contain some members that are no longer photosynthetic
28.
Gonostomatidae
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This name is also used to refer to some of the related Sternoptychidae, namely the genus Argyripnus. The Gonostomatidae are a family of marine fish, commonly named bristlemouths, lightfishes. It is a small family, containing only eight known genera and 32 species. The fossil record of this dates back to the Miocene epoch. Living bristlemouths were discovered by William Beebe in the early 1930s, the fish are mostly found in the Atlantic, Indian, and Pacific Oceans, although the species Cyclothone microdon may be found in Arctic waters. They have elongated bodies from 2 to 30 cm in length and they have a number of green or red light-producing photophores aligned along the undersides of their heads or bodies. Their chief common name, bristlemouth, comes from their odd, equally sized and they are typically black in color which provides camouflage from predators in deep, dark waters. Some classifications include the genera Pollichthys and Vinciguerria, but this article follows FishBase in placing them in the family Phosichthyidae, some classifications include species in the genus Zaphotias, but these are junior synonyms of the species Bonapartia pedaliota. Froese, Rainer, and Daniel Pauly, eds
29.
Swordfish
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Swordfish, also known as broadbills in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood and these fish are found widely in tropical and temperate parts of the Atlantic, Pacific, and Indian Oceans, and can typically be found from near the surface to a depth of 550 m. They commonly reach 3 m in length, and the maximum reported is 4.55 m in length and 650 kg in weight and they are the sole member of their family, Xiphiidae. The swordfish is named after its bill, which resembles a sword and this makes it superficially similar to other billfish such as marlin, but upon examination, their physiology is quite different and they are members of different families. They commonly reach 3 m in length, and the maximum reported is 4.55 m in length and 650 kg in weight, the International Game Fish Associations all-tackle angling record for a swordfish was a 1,182 lb specimen taken off Chile in 1953. Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and they reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years. The oldest swordfish found in a recent study were a 16-year-old female, swordfish ages are derived, with difficulty, from annual rings on fin rays rather than otoliths, since their otoliths are small in size. Swordfish are ectothermic animals, however, along some species of sharks, they have special organs next to their eyes to heat their eyes. Temperatures of 10 to 15 °C above the water temperature have been measured. The heating of the eyes greatly improves their vision, and consequently improves their ability to catch prey, of the 25, 000+ fish species, only 22 are known to have a mechanism to conserve heat. These include the swordfish, marlin, tuna, and some sharks, contrary to popular belief, the sword is not used to spear, but instead may be used to slash at its prey to injure the prey animal, to make for an easier catch. Mainly, the swordfish relies on its speed and agility in the water to catch its prey. It is undoubtedly among the fastest fish, but the basis for the frequently quoted speed of 97 km/h is unreliable, swordfish prefer water temperatures between 18 and 22 °C, but have the widest tolerance among billfish, and can be found from 5 to 27 °C. This highly migratory species typically moves towards colder regions to feed during the summer, swordfish feed daily, most often at night, when they rise to surface and near-surface waters in search of smaller fish. During the day, they occur to depths of 550 m and have exceptionally been recorded as deep as 2,878 m. Adults feed on a range of pelagic fish, such as mackerel, barracudinas, silver hake, rockfish, herring, and lanternfishes, but they also take demersal fish, squid. Large prey are typically slashed with the sword, while small are swallowed whole and they swim alone or in very loose aggregations, separated by as much as 10 m from a neighboring swordfish
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Squid
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Squid are cephalopods of the order Teuthida, which comprises around 304 species. Like all other cephalopods, squid have a head, bilateral symmetry, a mantle. Squid, like cuttlefish, have eight arms arranged in pairs, squid are strong swimmers and certain species can fly for short distances out of the water. Squid are members of the class Cephalopoda, subclass Coleoidea, order Teuthida, Teuthida is the largest cephalopod order with around 300 species classified into 29 families. The order Teuthida is a member of the superorder Decapodiformes, two other orders of decapodiform cephalopods are also called squid, although they are taxonomically distinct from Teuthida and differ recognizably in their gross anatomical features. They are the bobtail squid of order Sepiolida and the rams horn squid of the monotypic order Spirulida, the vampire squid, however, is more closely related to the octopuses than to any squid. Class Cephalopoda Subclass Nautiloidea, nautilus Subclass Coleoidea, squid, octopus, what before may have been the foot of the ancestor is modified into a complex set of tentacles and highly developed sense organs, including advanced eyes similar to those of vertebrates. The ancestral shell has been lost, with only an internal gladius, or pen, the pen is a feather-shaped internal structure that supports the squids mantle and serves as a site for muscle attachment. It is made of a chitin-like material, the main body mass is enclosed in the mantle, which has a swimming fin along each side. These fins, unlike in other organisms, are not the main source of locomotion in most species. The skin is covered in chromatophores, which enable the squid to change color to suit its surroundings, the underside is also almost always lighter than the topside, to provide camouflage from both prey and predator. Under the body are openings to the cavity, which contains the gills and openings to the excretory. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion via precise jet propulsion, in this form of locomotion, water is sucked into the mantle cavity and expelled out of the siphon in a fast, strong jet. The direction of the siphon can be changed, to suit the direction of travel, inside the mantle cavity, beyond the siphon, lies the visceral mass, which is covered by a thin, membranous epidermis. Under this are all the internal organs. The giant axon, which may be up to 1 mm in diameter in some species, innervates the mantle. As cephalopods, squid exhibit relatively high intelligence among invertebrates, for example, groups of Humboldt squid hunt cooperatively, using active communication. In females, the ink sac is hidden from view by a pair of white nidamental glands, also, red-spotted accessory nidamental glands are present
31.
Wolf eel
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The wolf eel is a species of wolffish from the North Pacific. It is monotypic within the genus Anarrhichthys and one of two genera in the family, the other being Anarhichas. A. ocellatus differs from true eels, because it has paired gill slits, the animal can grow to 2.4 m in length and 18.4 kg in weight. Unlike the grayish adults, the young are orange, the wolf eel usually lives for about 25 years. A. ocellatus is found in caves, crevices and rocky reefs from shallow waters to a depth of 226 m, ranging from the Sea of Japan, large wolf eels are curious and are rarely aggressive, but are capable of inflicting painful bites on humans. The male and female may pair for life and inhabit a cave together and this eel-like fish feeds on crustaceans, sea urchins, mussels, clams and some fishes, crushing them with its strong jaws. They have edible, sweet and savoury white flesh, in some coastal northwest Native American tribes, the wolf eel was referred to as the sacred doctorfish. Only the tribal healers were allowed to eat fish, as it was supposed to enhance their healing powers. North American Native Fishes Association Video of wolf eels eating a crab Nature Conservancy video on the wolf eel
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Cuttlefish
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Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda, which also includes squid, octopuses, cuttlefish have a unique internal shell, the cuttlebone. Despite their name, cuttlefish are not fish but molluscs, 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 15 to 25 cm, with the largest species, Sepia apama, reaching 50 cm in mantle length, cuttlefish eat small molluscs, crabs, shrimp, fish, octopus, worms, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds, the average life expectancy of a cuttlefish is about one to two years. Recent studies indicate cuttlefish are among the most intelligent invertebrates, cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates. The cuttle in cuttlefish comes from the Old English name for the species, cudele, which may be cognate with the Old Norse koddi, the Greco-Roman world valued the cuttlefish as a source of the unique brown pigment the creature releases from its siphon when it is alarmed. The word for it in both Greek and Latin, sepia, now refers to a pigment in English. The family Sepiidae, which contains all cuttlefish, inhabit tropical/temperate ocean waters and they are mostly shallow-water animals, although they are known to go to depths of about 600 m. By the time the family evolved, ostensibly in the Old World, the common cuttlefish, is found in the Mediterranean, and North and Baltic Seas, although it has been suggested populations occur as far south as South Africa. They are found in sublittoral depths, between the low line and the edge of the continental shelf, to about 180 m. The cuttlefish is listed under the Red List category of Least Concern by the IUCN Red List of Threatened Species, ocean acidification, however, caused largely by higher levels of carbon dioxide emitted into the atmosphere, is cited as a potential threat. Cuttlefish possess a structure called the cuttlebone, which is porous and is made of aragonite. The pores provide it with buoyancy, which the cuttlefish regulates by changing the ratio in the chambered cuttlebone via the ventral siphuncle. Each species cuttlebone has a shape, size, and pattern of ridges or texture. The cuttlebone is unique to cuttlefish, and is one of the features that distinguish them from their squid relatives, cuttlefish, like other cephalopods, have sophisticated eyes. The organogenesis and the structure of the cephalopod eye fundamentally differ from those of vertebrates such as humans. Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution, the cuttlefish pupil is a smoothly curving W-shape
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Vertebrate
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Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods
34.
Chain catshark
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The chain catshark or chain dogfish is a small, reticulated catshark that is biofluorescent. The species is common in the West Atlantic and Gulf of Mexico from Georges Bank in Massachusetts and it is harmless and rarely encountered by humans. It has very similar traits to the small-spotted catshark. The chain catshark is one of four species shown to possesses biofluorescent properties. In the Mid-Atlantic Bight, the chain dogfish is found along the continental shelf. The shark occupies depths of 58 to 359 meters and occupies shallower depths in the region compared to southern areas. Due to the depth distribution, it has been suggested that the shark does not perform large-scale migrations. Temperature is thought to limit the distribution in northern areas. Although bands of water at the edge of the shelf have been observed. Sizes of the range from 0.36 feet, to 1.5 feet. Females tend to be larger at maturity, being 1.7 feet long compared to their counterparts at 1.64 feet. The catshark spends the daytime resting at the bottom, usually in contact with certain structures and it has been observed with large burrowing cerianthid anemone tubes and boulders. The bottom rubble is thought to be used as a camouflage with the spotted surface. Adult sharks tend to prefer rough bottoms, creating a difficulty for trawl sampling, the chain catshark has been known to feed on squid, bony fish, polychaetes and crustaceans. In aquaria, they are relatively motionless, only swimming occasionally, in the female chain catshark, follicle development has been correlated to nidamental gland size, thus, they are considered mature when they have a fully developed nidamental gland or shell gland. This is marked by the growth to 18 mm or more in width. Sexual maturity in the female is seen at 520 mm in length under normal conditions, there has been evidence however that some northern populations of the shark may mature at a smaller size. In the male catshark, testis development is correlated to clasper size, claspers have been observed to develop after the shark is 490 mm and become mature at 500 mm. Observed mating between the species suggests biting plays an element and that mating occurs repeatedly
35.
Fluorescence
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Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
36.
Biomass
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Biomass is an industry term for getting energy by burning wood, and other organic matter. It has become popular among power stations, which switch from coal to biomass to comply with the law. Biomass most often refers to plants or plant-based materials that are not used for food or feed, as an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are classified into, thermal, chemical. Historically, humans have harnessed biomass-derived energy since the time people began burning wood to make fire. Even today, biomass is the source of fuel for domestic use in many developing countries. Biomass is all biologically-produced matter based in carbon, hydrogen and oxygen, the estimated biomass production in the world is 104.9 petagrams of carbon per year, about half in the ocean and half on land. Wood remains the largest biomass energy source today, examples include forest residues, yard clippings, wood chips, wood energy is derived by using lignocellulosic biomass as fuel. Harvested wood may be used directly as a fuel or collected from waste streams to be processed into pellet fuel or other forms of fuels. The largest source of energy from wood is pulping liquor or black liquor, in the second sense, biomass includes plant or animal matter that can be converted into fibers or other industrial chemicals, including biofuels. Based on the source of biomass, biofuels are classified broadly into two major categories, first-generation biofuels are derived from sources such as sugarcane and corn starch. Sugars present in this biomass are fermented to produce bioethanol, a fuel which can be used directly in a fuel cell to produce electricity or serve as an additive to gasoline. However, utilizing food-based resources for production only aggravates the food shortage problem. Second-generation biofuels, on the hand, utilize non-food-based biomass sources such as agriculture. These biofuels mostly consist of lignocellulosic biomass, which is not edible and is a waste for many industries. Despite being the alternative, economical production of second-generation biofuel is not yet achieved due to technological issues. These issues arise due to chemical inertness and structural rigidity of lignocellulosic biomass. Plant energy is produced by crops grown for use as fuel that offer high biomass output per hectare with low input energy
37.
Seafood
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Seafood is any form of sea life regarded as food by humans. Seafood prominently includes fish and shellfish, shellfish include various species of molluscs, crustaceans, and echinoderms. Historically, sea mammals such as whales and dolphins have been consumed as food, edible sea plants, such as some seaweeds and microalgae, are widely eaten as seafood around the world, especially in Asia. In North America, although not generally in the United Kingdom, for the sake of completeness, this article includes all edible aquatic life. The harvesting of seafood is usually known as fishing or hunting. Seafood is often distinguished from meat, although it is still animal and is excluded in a vegetarian diet. Seafood is an important source of protein in many diets around the world, most of the seafood harvest is consumed by humans, but a significant proportion is used as fish food to farm other fish or rear farm animals. Some seafoods are used as food for other plants, in these ways, seafoods are indirectly used to produce further food for human consumption. Products, such as oil and spirulina tablets are also extracted from seafoods. Some seafood is feed to fish, or used to feed domestic pets, such as cats. The harvesting, processing, and consuming of seafoods are ancient practices with archaeological evidence dating back well into the Paleolithic, isotopic analysis of the skeletal remains of Tianyuan man, a 40, 000-year-old modern human from eastern Asia, has shown that he regularly consumed freshwater fish. Archaeology features such as middens, discarded fish bones and cave paintings show that sea foods were important for survival. During this period, most people lived a lifestyle and were, of necessity. However, where there are examples of permanent settlements such as those at Lepenski Vir. The ancient river Nile was full of fish, fresh and dried fish were a food for much of the population. The Egyptians had implements and methods for fishing and these are illustrated in scenes, drawings. Some representations hint at fishing being pursued as a pastime, fishing scenes are rarely represented in ancient Greek culture, a reflection of the low social status of fishing. However, Oppian of Corycus, a Greek author wrote a treatise on sea fishing
38.
Fishing industry
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The fishing industry includes any industry or activity concerned with taking, culturing, processing, preserving, storing, transporting, marketing or selling fish or fish products. It is defined by the Food and Agriculture Organization as including recreational, subsistence and commercial fishing, and the harvesting, processing, the commercial activity is aimed at the delivery of fish and other seafood products for human consumption or as input factors in other industrial processes. Directly or indirectly, the livelihood of over 500 million people in developing countries depends on fisheries and it is also referred to as the seafood industry, although non-food items such as pearls are included among its products. The traditional sector, comprises enterprises and individuals associated with fisheries resources from which aboriginal people derive products in accordance with their traditions, in addition,1.3 million tons of aquatic plants were captured in wild fisheries and 14.8 million tons were produced by aquaculture. The number of fish caught in the wild has been estimated at 0. 97-2.7 trillion per year. Following is a table of the 2011 world fishing industry harvest in tonnes by capture and by aquaculture. The top producing countries were, in order, the Peoples Republic of China, Peru, Japan and those countries accounted for more than half of the worlds production, China alone accounted for a third of the worlds production. Aquaculture is the cultivation of aquatic organisms, unlike fishing, aquaculture, also known as aquafarming, is the cultivation of aquatic populations under controlled conditions. Mariculture refers to aquaculture practiced in marine environments, particular kinds of aquaculture include algaculture, fish farming, shrimp farming, shellfish farming, and the growing of cultured pearls. Fish farming involves raising fish commercially in tanks or enclosed pools, fish species raised by fish farms include carp, salmon, tilapia, catfish and cod. Increasing demands on wild fisheries by commercial fishing operations have caused widespread overfishing, fish farming offers an alternative solution to the increasing market demand for fish and fish protein. Fish processing is the processing of fish delivered by commercial fisheries, the larger fish processing companies have their own fishing fleets and independent fisheries. The products of the industry are usually sold wholesale to grocery chains or to intermediaries, fish processing can be subdivided into two categories, fish handling and fish products manufacturing. Aspects of fish processing occur on fishing vessels, fish processing vessels, fisheries are estimated to currently provide 16% of the world populations protein. The flesh of fish are primarily valued as a source of food. Other marine life taken as food includes shellfish, crustaceans, sea cucumber, jellyfish, fish and other marine life can also be used for many other uses, pearls and mother-of-pearl, sharkskin and rayskin. Sea horses, star fish, sea urchins and sea cucumber are used in traditional Chinese medicine, tyrian purple is a pigment made from marine snails, sepia is a pigment made from the inky secretions of cuttlefish. Fish glue has long valued for its use in all manner of products
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Fish farming
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Fish farming or pisciculture involves raising fish commercially in tanks or enclosures, usually for food. It is the form of aquaculture, while other methods may fall under mariculture. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species used in farming are carp, tilapia, salmon. Demand is increasing for fish and fish protein, which has resulted in widespread overfishing in wild fisheries, china provides 62% of the worlds farmed fish. As of 2016, more than 50% of seafood was produced by aquaculture, Farming carnivorous fish, such as salmon, does not always reduce pressure on wild fisheries, since carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tonnes worth about $US60 billion, Aquaculture makes use of local photosynthetic production or fish that are fed with external food supply. Growth is limited by food, commonly zooplankton feeding on pelagic algae or benthic animals, such as crustaceans. Tilapia filter feed directly on phytoplankton, which makes higher production possible, photosynthetic production can be increased by fertilizing pond water with artificial fertilizer mixtures, such as potash, phosphorus, nitrogen, and microelements. Another issue is the risk of algal blooms, when temperatures, nutrient supply, and available sunlight are optimal for algal growth, algae multiply at an exponential rate, eventually exhausting nutrients and causing a subsequent die-off. The decaying algal biomass depletes the oxygen in the water because it blocks out the sun and pollutes it with organic and inorganic solutes. An alternate option is to use a system such as that of Veta la Palma in Spain. Despite these limitations, significant fish farming industries use these methods, in the Czech Republic, thousands of natural and seminatural ponds are harvested each year for trout and carp. The large ponds around Trebon built from around 1650 are still in use, in these kinds of systems fish production per unit of surface can be increased at will, as long as sufficient oxygen, fresh water and food are provided. Because of the requirement of sufficient fresh water, a water purification system must be integrated in the fish farm. One way to achieve this is to combine hydroponic horticulture and water treatment, the exception to this rule are cages which are placed in a river or sea, which supplements the fish crop with sufficient oxygenated water. Some environmentalists object to this practice, however, these higher protein level requirements are a consequence of the higher feed efficiency of aquatic animals. Fish such as salmon have an FCR around 1.1 kg of feed per kg of salmon whereas chickens are in the 2.5 kg of feed per kg of chicken range
40.
Fish oil
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Fish oil is oil derived from the tissues of oily fish. Nonetheless, fish oil supplement studies have failed to support claims of preventing heart attacks or strokes, the fish used as sources do not actually produce omega-3 fatty acids, but instead accumulate them by consuming either microalgae or prey fish that have accumulated omega-3 fatty acids. For this reason, the United States Environmental Protection Agency recommends limiting consumption of fish species due to high levels of the toxic contaminant mercury. Dioxin, PCBs and chlordane are also present, fish oil is used as a component in aquaculture feed. More than 50 percent of the fish oil used in aquaculture feed is fed to farmed salmon. Marine and freshwater fish oil vary in contents of arachidonic acid, EPA, the various species range from lean to fatty and their oil content in the tissues has been shown to vary from 0. 7% to 15. 5%. They also differ in their effects on organ lipids, studies have revealed that there is no relation between total fish intake or estimated omega−3 fatty acid intake from all fish, and serum omega−3 fatty acid concentrations. Only fatty fish intake, particularly salmonid, and estimated EPA + DHA intake from fatty fish has been observed to be associated with increase in serum EPA + DHA. The omega-3 fatty acids in fish oil are thought to be beneficial in treating hypertriglyceridemia, in 2005, fish oil production declined in all main producing countries with the exception of Iceland. The most widely available source of EPA and DHA is cold-water oily fish, such as salmon, herring, mackerel, anchovies. Oils from these fish have a profile of around seven times as much omega-3 oils as omega-6 oils, other oily fish, such as tuna, also contain omega-3 in somewhat lesser amounts. Although fish is a source of omega-3 oils, fish do not synthesize them. The Food and Drug Administration recommends not exceeding 3 grams per day of EPA + DHA from all sources, some evidence indicated an association between high blood levels of omega-3 fatty acids and an increased prostate cancer risk. Fish oil supplement studies have failed to support claims of preventing heart attacks or strokes and it then lists 27 other conditions for which there is less evidence. Very large intakes of fish oil/omega-3 fatty acids may increase the risk of hemorrhagic stroke, there is also some evidence that fish oil may have a beneficial effect on certain abnormal heart rhythms. However, a 2012 meta-analysis found no significant benefit. A2008 meta-study by the Canadian Medical Association Journal found fish oil supplementation did not demonstrate any benefit to cardiac patients with ventricular arrhythmias. There have been some human trials that have concluded that consuming omega-3 fatty acids slightly reduces blood pressure and it is important to note that because omega-3 fatty acids can increase the risk of bleeding, a qualified healthcare provider should be consulted before supplementing with fish oil
41.
The New York Times
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The New York Times is an American daily newspaper, founded and continuously published in New York City since September 18,1851, by The New York Times Company. The New York Times has won 119 Pulitzer Prizes, more than any other newspaper, the papers print version in 2013 had the second-largest circulation, behind The Wall Street Journal, and the largest circulation among the metropolitan newspapers in the US. The New York Times is ranked 18th in the world by circulation, following industry trends, its weekday circulation had fallen in 2009 to fewer than one million. Nicknamed The Gray Lady, The New York Times has long been regarded within the industry as a newspaper of record. The New York Times international version, formerly the International Herald Tribune, is now called the New York Times International Edition, the papers motto, All the News Thats Fit to Print, appears in the upper left-hand corner of the front page. On Sunday, The New York Times is supplemented by the Sunday Review, The New York Times Book Review, The New York Times Magazine and T, some other early investors of the company were Edwin B. Morgan and Edward B. We do not believe that everything in Society is either right or exactly wrong, —what is good we desire to preserve and improve, —what is evil, to exterminate. In 1852, the started a western division, The Times of California that arrived whenever a mail boat got to California. However, when local California newspapers came into prominence, the effort failed, the newspaper shortened its name to The New-York Times in 1857. It dropped the hyphen in the city name in the 1890s, One of the earliest public controversies it was involved with was the Mortara Affair, the subject of twenty editorials it published alone. At Newspaper Row, across from City Hall, Henry Raymond, owner and editor of The New York Times, averted the rioters with Gatling guns, in 1869, Raymond died, and George Jones took over as publisher. Tweed offered The New York Times five million dollars to not publish the story, in the 1880s, The New York Times transitioned gradually from editorially supporting Republican Party candidates to becoming more politically independent and analytical. In 1884, the paper supported Democrat Grover Cleveland in his first presidential campaign, while this move cost The New York Times readership among its more progressive and Republican readers, the paper eventually regained most of its lost ground within a few years. However, the newspaper was financially crippled by the Panic of 1893, the paper slowly acquired a reputation for even-handedness and accurate modern reporting, especially by the 1890s under the guidance of Ochs. Under Ochs guidance, continuing and expanding upon the Henry Raymond tradition, The New York Times achieved international scope, circulation, in 1910, the first air delivery of The New York Times to Philadelphia began. The New York Times first trans-Atlantic delivery by air to London occurred in 1919 by dirigible, airplane Edition was sent by plane to Chicago so it could be in the hands of Republican convention delegates by evening. In the 1940s, the extended its breadth and reach. The crossword began appearing regularly in 1942, and the section in 1946
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Pelagic fish
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The marine pelagic environment is the largest aquatic habitat on Earth, occupying 1,370 million cubic kilometres, and is the habitat for 11% of known fish species. The oceans have a depth of 4000 metres. About 98% of the water volume is below 100 metres. Marine pelagic fish can be divided into pelagic coastal fish and oceanic pelagic fish, coastal fish inhabit the relatively shallow and sunlit waters above the continental shelf, while oceanic fish inhabit the vast and deep waters beyond the continental shelf. Pelagic fish range in size from small forage fish, such as herrings and sardines, to large apex predator oceanic fishes, such as bluefin tuna. They are usually agile swimmers with streamlined bodies, capable of sustained cruising on long-distance migrations, the Indo-Pacific sailfish, an oceanic pelagic fish, can sprint at over 110 kilometres per hour. Some tuna species cruise across the Pacific Ocean, many pelagic fish swim in schools weighing hundreds of tonnes. Others are solitary, like the ocean sunfish weighing over 500 kilograms. Epipelagic fish inhabit the epipelagic zone, the epipelagic zone is the water from the surface of the sea down to 200 metres. It is also referred to as the waters or the sunlit zone. The photic zone is defined as the surface waters down to the point where the sunlight has attenuated to 1% of the surface value and this depth depends on how turbid the water is, but in clear water can extend to 200 metres, coinciding with the epipelagic zone. The photic zone has sufficient light for phytoplankton to photosynthese, the epipelagic zone is vast, and is the home for most pelagic fish. The zone is well lit so visual predators can use their eyesight, is well mixed and oxygenated from wave action. However, it is an almost featureless habitat and this lack of habitat diversity results in a lack of species diversity, so the zone supports less than 2% of the worlds known fish species. Epipelagic fish can be divided into small forage fish and larger predator fish which feed on them. Forage fish school and filter feed on plankton, most epipelagic fish have streamlined bodies capable of sustained cruising on migrations. In general, predatory and forage fish share the same morphological features, predator fish are usually fusiform with large mouths, smooth bodies, and deeply forked tails. Many use vision to predate zooplankton or smaller fish, while others feed on plankton
43.
Physical oceanography
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Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters. Physical oceanography is one of several sub-domains into which oceanography is divided, others include biological, chemical and geological oceanography. Physical oceanography may be subdivided into descriptive and dynamical physical oceanography, descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precise as possible. Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and these are part of the large field of Geophysical Fluid Dynamics that is shared together with meteorology. The fundamental role of the oceans in shaping Earth is acknowledged by ecologists, geologists, meteorologists, climatologists, an Earth without oceans would truly be unrecognizable. Roughly 97% of the water is in its oceans. The tremendous heat capacity of the oceans moderates the planets climate, the oceans influence extends even to the composition of volcanic rocks through seafloor metamorphism, as well as to that of volcanic gases and magmas created at subduction zones. Though this apparent discrepancy is great, for land and sea, the respective extremes such as mountains and trenches are rare. Because the vast majority of the oceans volume is deep water. The same percentage falls in a salinity range between 34–35 ppt, there is still quite a bit of variation, however. Surface temperatures can range from below freezing near the poles to 35 °C in restricted tropical seas, in terms of temperature, the oceans layers are highly latitude-dependent, the thermocline is pronounced in the tropics, but nonexistent in polar waters. The halocline usually lies near the surface, where evaporation raises salinity in the tropics and these variations of salinity and temperature with depth change the density of the seawater, creating the pycnocline. Energy for the ocean circulation comes from solar radiation and gravitational energy from the sun, perhaps three quarters of this heat is carried in the atmosphere, the rest is carried in the ocean. The atmosphere is heated from below, which leads to convection, by contrast the ocean is heated from above, which tends to suppress convection. Instead ocean deep water is formed in regions where cold salty waters sink in fairly restricted areas. This is the beginning of the thermohaline circulation, oceanic currents are largely driven by the surface wind stress, hence the large-scale atmospheric circulation is important to understanding the ocean circulation. The Hadley circulation leads to Easterly winds in the tropics and Westerlies in mid-latitudes and this leads to slow equatorward flow throughout most of a subtropical ocean basin. The return flow occurs in an intense, narrow, poleward western boundary current, like the atmosphere, the ocean is far wider than it is deep, and hence horizontal motion is in general much faster than vertical motion
44.
Wind wave
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In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of bodies of water. They result from the wind blowing over an area of fluid surface, Waves in the oceans can travel thousands of miles before reaching land. Wind waves on Earth range in size from small ripples, to waves over 100 ft high, when directly generated and affected by local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swells, more generally, a swell consists of wind-generated waves that are not significantly affected by the local wind at that time. They have been generated elsewhere or some time ago, wind waves in the ocean are called ocean surface waves. Wind waves have an amount of randomness, subsequent waves differ in height, duration. The key statistics of wind waves in evolving sea states can be predicted with wind wave models, although waves are usually considered in the water seas of Earth, the hydrocarbon seas of Titan may also have wind-driven waves. The great majority of large breakers seen at a result from distant winds. Water depth All of these work together to determine the size of wind waves. Further exposure to that wind could only cause a dissipation of energy due to the breaking of wave tops. Waves in an area typically have a range of heights. For weather reporting and for analysis of wind wave statistics. This figure represents an average height of the highest one-third of the waves in a time period. The significant wave height is also the value a trained observer would estimate from visual observation of a sea state, given the variability of wave height, the largest individual waves are likely to be somewhat less than twice the reported significant wave height for a particular day or storm. Wave formation on a flat water surface by wind is started by a random distribution of normal pressure of turbulent wind flow over the water. This pressure fluctuation produces normal and tangential stresses in the surface water and it is assumed that, The water is originally at rest. There is a distribution of normal pressure to the water surface from the turbulent wind. Correlations between air and water motions are neglected, the second mechanism involves wind shear forces on the water surface
45.
Airy wave theory
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In fluid dynamics, Airy wave theory gives a linearised description of the propagation of gravity waves on the surface of a homogeneous fluid layer. The theory assumes that the layer has a uniform mean depth. This theory was first published, in form, by George Biddell Airy in the 19th century. Further, several second-order nonlinear properties of gravity waves, and their propagation. Airy wave theory is also a good approximation for tsunami waves in the ocean and this linear theory is often used to get a quick and rough estimate of wave characteristics and their effects. This approximation is accurate for small ratios of the height to water depth. Airy wave theory uses a potential approach to describe the motion of gravity waves on a fluid surface. This is due to the fact that for the part of the fluid motion. Airy wave theory is used in ocean engineering and coastal engineering. Diffraction is one of the effects which can be described with Airy wave theory. Further, by using the WKBJ approximation, wave shoaling and refraction can be predicted, earlier attempts to describe surface gravity waves using potential flow were made by, among others, Laplace, Poisson, Cauchy and Kelland. But Airy was the first to publish the correct derivation and formulation in 1841, soon after, in 1847, the linear theory of Airy was extended by Stokes for non-linear wave motion – known as Stokes wave theory – correct up to third order in the wave steepness. Even before Airys linear theory, Gerstner derived a nonlinear wave theory in 1802. Airy wave theory is a theory for the propagation of waves on the surface of a potential flow. The waves propagate along the surface with the phase speed cp. The angular wavenumber k and frequency ω are not independent parameters, surface gravity waves on a fluid are dispersive waves – exhibiting frequency dispersion – meaning that each wavenumber has its own frequency and phase speed. Note that in engineering the wave height H – the difference in elevation between crest and trough – is often used, H =2 a and a =12 H, underneath the surface, there is a fluid motion associated with the free surface motion. While the surface shows a propagating wave, the fluid particles are in an orbital motion
