Opuntia called prickly pear, is a genus in the cactus family, Cactaceae. Prickly pears are known as tuna, nopal from the Nahuatl word nōpalli for the pads, or nostle, from the Nahuatl word nōchtli for the fruit; the genus is named for the Ancient Greek city of Opus, according to Theophrastus, an edible plant grew and could be propagated by rooting its leaves. The most common culinary species is the Indian fig opuntia. O. ficus-indica is a large trunk-forming segmented cactus which may grow to 5–7 metres with a crown of 3 metres in diameter and a trunk diameter of 1 metre. Cladodes may be spineless. Prickly pears grow with flat, rounded cladodes containing large, fixed spines and small, hairlike prickles called glochids that adhere to skin or hair detach from the plant; the flowers are large, solitary and epiperigynous, with a perianth consisting of distinct, spirally arranged tepals and a hypanthium. The stamens are numerous and in spiral or whorled clusters, the gynoecium has numerous inferior ovaries per carpel.
Placentation is parietal, the fruit is a berry with arillate seeds. Prickly pear species can vary in habit. O. ficus-indica thrives in regions with mild winters having a prolonged dry spell followed by hot summers with occasional rain and low humidity. A mean annual rainfall of 350–500 millimetres provides good growth rates. O. ficus-indica proliferates in various soils ranging from sub-acid to sub-alkaline, with clay content not exceeding 15-20% and the soil well-drained. The shallow root system enables the plant to grow in shallow, loose soils, such as on mountain slopes. Opuntia spreads into large clonal colonies, which contribute to its being considered a noxious weed in some places. Animals that eat Opuntia include Cyclura rock iguanas; the fruit are relished by many arid land animals, chiefly birds, which thus help distribute the seeds. Opuntia pathogens include the sac fungus Sammons' Opuntia virus; the ant Crematogaster opuntiae and the spider Theridion opuntia are named because of their association with prickly pear cacti.
Like most true cactus species, prickly pears are native only to the Americas. Through human actions, they have since been introduced to many other areas of the world. Prickly pear species are found in abundance in Mexico in the central and western regions, in the Caribbean islands. In the United States, prickly pears are native to many areas of the arid, semi-arid, drought-prone Western and South Central United States, including the lower elevations of the Rocky Mountains and southern Great Plains, where species such as Opuntia phaeacantha and Opuntia polyacantha become dominant, to the desert Southwest, where several types are endemic. Prickly pear cactus is native to sandy coastal beach scrub environments of the East Coast from Florida to southern Connecticut. Opuntia species are the most cold-tolerant of the lowland cacti, extending into western and southern Canada. Prickly pears produce a fruit eaten in Mexico and in the Mediterranean region, known as tuna; the fruit can be wine-red, green, or yellow-orange.
In the Galápagos Islands, six different species are found: O. echios, O. galapageia, O. helleri, O. insularis, O. saxicola, O. megasperma. These species are divided into 14 different varieties. For this reason, they have been described as "an excellent example of adaptive radiation". On the whole, islands with tall, trunked varieties have giant tortoises, islands lacking tortoises have low or prostrate forms of Opuntia. Prickly pears are a prime source of food for the common giant tortoises in the Galápagos islands so they are important in the food web. Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen; this movement can be seen by poking the anthers of an open Opuntia flower. The same trait has evolved convergently in other cacti; the first introduction of prickly pears into Australia is ascribed to Governor Philip and the earliest colonists in 1788. Brought from Brazil to Sydney, prickly pear grew in Sydney, New South Wales, where they were rediscovered in a farmer's garden in 1839.
They appear to have spread from New South Wales and caused great ecological damage in the eastern states. They are found in the Mediterranean region of Northern Africa in Tunisia, where they grow all over the countryside, in parts of southern Europe Spain, where they grow in the east, south-east and south of the country, in Malta, where they grow all over the islands, they can be found in enormous numbers in parts of South Africa, where they were introduced from South America. Prickly pears are considered an invasive species in Australia, South Africa, Hawaii, among other locations. Prickly pears were imported into Europe during the 1500s and Australia in the 18th century for gardens, were used as a natural agricultural fencing and in an attempt to establish a cochineal dye industry. They
A fish hook or fishhook is a device for catching fish either by impaling them in the mouth or, more by snagging the body of the fish. Fish hooks have been employed for centuries by anglers to catch fresh and saltwater fish. In 2005, the fish hook was chosen by Forbes as one of the top twenty tools in the history of man. Fish hooks are attached to some form of line or lure which connects the caught fish to the angler. There is an enormous variety of fish hooks in the world of fishing. Sizes, designs and materials are all variable depending on the intended purpose of the fish hook. Fish hooks are manufactured for a range of purposes from general fishing to limited and specialized applications. Fish hooks are designed to hold various types of artificial, dead or live baits; the fish hook or similar device has been made by man for many thousands of years. The world's oldest fish hooks were discovered in Sakitari Cave in Okinawa Island dated between 22,380 and 22,770 years old, they are older than the fish hooks from the Jerimalai cave in East Timor dated between 23,000 and 16,000 years old, New Ireland in Papua New Guinea dated 20,000 to 18,000 years old.
An early written reference to a fish hook is found with reference to the Leviathan in the Book of Job 41:1. Fish hooks have been crafted from all sorts of materials including wood and human bone, shells, bronze, up to present day materials. In many cases, hooks were created from multiple materials to leverage the strength and positive characteristics of each material. Norwegians as late as the 1950s still used juniper wood to craft Burbot hooks. Quality steel hooks began to make their appearance in Europe in the 17th century and hook making became a task for specialists. Referred to parts of a fish hook are: its point, the sharp end that penetrates the fish's mouth or flesh. In many cases, hooks are described by using these various parts of the hook, for example: wide gape, long shank, hollow point or out turned eye. Contemporary hooks are manufactured from either high-carbon steel, steel alloyed with vanadium, or stainless steel, depending on application. Most quality fish hooks are covered with some form of corrosion-resistant surface coating.
Corrosion resistance is required not only when hooks are used in saltwater, but while they are stored. Additionally, coatings provide aesthetic value to the hook. At a minimum, hooks designed for freshwater use are coated with a clear lacquer, but hooks are coated with gold, Teflon and different colors. There are a large number of different types of fish hooks. At the macro level, there are bait hooks, fly hooks and lure hooks. Within these broad categories there are wide varieties of hook types designed for different applications. Hook types differ in shape, materials and barbs, eye type, in their intended application; when individual hook types are designed the specific characteristics of each of these hook components are optimized relative to the hook's intended purpose. For example, a delicate dry fly hook is made of thin wire with a tapered eye because weight is the overriding factor. Whereas Carlisle or Aberdeen light wire bait hooks make use of thin wire to reduce injury to live bait but the eyes are not tapered because weight is not an issue.
Many factors contribute to hook design, including corrosion resistance, strength, hooking efficiency, whether the hook is being used for specific types of bait, on different types of lures or for different styles of flies. For each hook type, there are ranges of acceptable sizes. For all types of hooks, sizes range from 32 to 20/0. Hook shapes and names are as varied as fish themselves. In some cases hooks are identified by a traditional or historic name, e.g. Aberdeen, Limerick or O'Shaughnessy. In other cases, hooks are identified by their general purpose or have included in their name, one or more of their physical characteristics; some manufacturers just give their hooks model numbers and describe their general purpose and characteristics. For example: Eagle Claw: 139 is a Snelled Baitholder, Down Eye, Two Slices, Medium Wire Lazer Sharp: L2004EL is a Circle Sea, Wide Gap, Non-Offset, Ringed Eye, Light Wire Mustad Model: 92155 is a Beak Baitholder hook Mustad Model: 91715D is an O'Shaughnessy Jig Hook, 90 degree angle TMC Model 300: Streamer D/E, 6XL, Heavy wire, Bronze TMC Model 200R: Nymph & Dry Fly Straight eye, 3XL, Standard wire, Semidropped point, BronzeThe shape of the hook shank can vary from straight to all sorts of curves, kinks and offsets.
These different shapes contribute in some cases to better hook penetration, fly imitations or bait holding ability. Many hooks intended to hold dead or artificial baits have sliced shanks which create barbs for better baiting holding ability. Jig hooks are designed to have lead weight molded onto the hook shank. Hook descriptions may include shank length as standard, extra long, 2XL, etc. and wire size such as fine wire, extra heavy, 2X heavy, etc. Hooks are designed as either single hooks—a single eye and point.
West Indian manatee
The West Indian manatee or "sea cow" known as American manatee, is the largest surviving member of the aquatic mammal order Sirenia. The West Indian manatee is a species distinct from the African manatee. Based on genetic and morphological studies, the West Indian manatee is divided into two subspecies, the Florida manatee and the Antillean or Caribbean manatee. However, recent genetic research suggests that the West Indian manatee consists of three groups, which are more or less geographically distributed as: Florida and the Greater Antilles; the West Indian Manatee was placed on the Endangered Species List in the 1970s, when there were only several hundred left, it has been of great conservation concern to federal, state and nonprofit organizations to protect these species from natural and human-induced threats like collisions with boats. On March 30, 2017, the US Secretary of the Interior Ryan Zinke announced the federal reclassification of the manatee from endangered to threatened as the number of sea cows had increased to over 6,000.
Like the other sirenians, the West Indian manatee has adapted to aquatic life, having no hind limbs. Pelage cover is sparsely distributed across the body, which may play a role in reducing the build-up of algae on their thick skin; the average West Indian manatee is about 2.7–3.5 m long and weighs 200–600 kg, with females larger than males. The difference between the two subspecies of the West Indian manatee is that the Florida manatee is reported as being larger in size compared to Antillean manatee; the largest individual on record measured 4.6 m long. This manatee's color is brown, its flippers have either three or four nails. As its name implies, the West Indian manatee lives in the West Indies, or Caribbean in shallow coastal areas. However, it is known to withstand large changes in water salinity, so has been found in shallow rivers and estuaries, it can live in fresh and saline water. It is limited to the tropics and subtropics due to an low metabolic rate and lack of a thick layer of insulating body fat.
While this is a occurring species along coastal southern Florida, during summer, this large mammal has been found as far north as Dennis, as far west as Texas. A manatee was spotted in the Wolf River in Memphis, Tennessee in 2006; the Florida manatee, a subspecies of the West Indian manatee, is the largest of all living sirenians. Florida manatees inhabit the most northern limit of sirenian habitats. Over three decades of research by universities, governmental agencies, NGOs have contributed to understanding of Florida manatee ecology and behavior, they are found in freshwater rivers, in estuaries, in the coastal waters of the Gulf of Mexico and the Atlantic Ocean. Florida manatees may live to be more than 28 years old in the wild, one captive manatee, "Snooty", lived for 69 years. Large concentrations of Florida manatees are located in the Crystal River and Blue Springs regions in central and north Florida, as well as along the Atlantic Coast, Florida Gulf Coast; the other subspecies of the West Indian manatee is sometimes referred to as the Antillean manatee.
Antillean manatees are sparsely distributed throughout the Caribbean and the northwestern Atlantic Ocean, from Mexico, east to the Greater Antilles, south to Brazil. They are found in The Bahamas, French Guiana, Guyana, Venezuela, Panama, Costa Rica, Honduras, Belize, Cuba, the Dominican Republic and Puerto Rico. Antillean manatees were hunted by local natives and sold to European explorers for food. Today, they are threatened by loss of habitat, entanglement with fishing gear, vessel strikes; the West Indian manatee is agile in water, individuals have been seen doing rolls and swimming upside-down. Manatees are not territorial and do not have complex predator avoidance behavior, as they have evolved in areas without natural predators; the common predators of marine mammals, such as killer whales and large sharks, are found in habitats inhabited by this species. Based upon their behavior, Bauer et al. suggest that manatees may share the characteristic of pheromonal communication with their relative, the elephant.
Some scientists have observed that manatees form long periods of mating herds when wandering males come across estrous females, which indicates the possibility that males are able to sense the estrogen or other chemical indicators. Other scientists have observed that manatees can communicate information to each other through their vocalization patterns. Evidence suggests that there are sex and age-related differences in the vocalization structure of common squeaks and screeches in adult males, adult females, juveniles; this may be an indication of vocal individuality among manatees. An increase in Manatee vocalization after a vocal playback stimulus shows that they may be able to recognize another Manatee's individual voice; this behavior in manatees is found between mother and calf interactions. However, vocalization can still be found in a variety of social interactions within groups of ma
The white-tailed deer known as the whitetail or Virginia deer, is a medium-sized deer native to the United States, Mexico, Central America, South America as far south as Peru and Bolivia. It has been introduced to New Zealand, Jamaica, Puerto Rico, the Bahamas, the Lesser Antilles, some countries in Europe, such as Finland, the Czech Republic and Serbia. In the Americas, it is the most distributed wild ungulate. In North America, the species is distributed east of the Rocky Mountains as well as in most of Mexico, aside from Lower California, in southwestern Arizona. IIt is replaced by the black-tailed or mule deer from that point west. However, it is found in mixed deciduous riparian corridors, river valley bottomlands, lower foothills of the northern Rocky Mountain region from South Dakota west to eastern Washington and eastern Oregon and north to northeastern British Columbia and southern Yukon, including in the Montana Valley and Foothill grasslands; the conversion of land adjacent to the Canadian Rockies into agriculture use and partial clear-cutting of coniferous trees has been favorable to the white-tailed deer and has pushed its distribution to as far north as Yukon.
Populations of deer around the Great Lakes have expanded their range northwards, due to conversion of land to agricultural uses favoring more deciduous vegetation, local caribou and moose populations. The westernmost population of the species, known as the Columbian white-tailed deer, once was widespread in the mixed forests along the Willamette and Cowlitz River valleys of western Oregon and southwestern Washington, but today its numbers have been reduced, it is classified as near-threatened; this population is separated from other white-tailed deer populations. Some taxonomists have attempted to separate white-tailed deer into a host of subspecies, based on morphological differences. Genetic studies, suggest fewer subspecies within the animal's range, as compared to the 30 to 40 subspecies that some scientists described in the last century; the Florida Key deer, O. v. clavium, the Columbian white-tailed deer, O. v. leucurus, are both listed as endangered under the U. S. Endangered Species Act.
In the United States, the Virginia white-tail, O. v. virginianus, is among the most widespread subspecies. The white-tailed deer species has tremendous genetic variation and is adaptable to several environments. Several local deer populations in the southern states, are descended from white-tailed deer transplanted from various localities east of the Continental Divide; some of these deer populations may have been from as far north as the Great Lakes region to as far west as Texas, yet are quite at home in the Appalachian and Piedmont regions of the south. These deer, over time, have intermixed with the local indigenous deer populations. Central and South America have a complex number of white-tailed deer subspecies that range from Guatemala to as far south as Peru; this list of subspecies of deer is more exhaustive than the list of North American subspecies, the number of subspecies is questionable. However, the white-tailed deer populations in these areas are difficult to study, due to overhunting in many parts and a lack of protection.
Some areas no longer carry deer, so assessing the genetic difference of these animals is difficult. Some subspecies names, ordered alphabetically: O. v. acapulcensis – Acapulco white-tailed deer O. v. borealis – northern white-tailed deer O. v. carminis – Carmen Mountains white-tailed deer O. v. clavium – Key deer or Florida Keys white-tailed deer O. v. chiriquensis – Chiriqui white-tailed deer O. v. couesi – Coues' white-tailed deer, Arizona white-tailed deer, or fantail deer O. v. dakotensis – Dakota white-tailed deer or northern plains white-tailed deer O. v. hiltonensis – Hilton Head Island white-tailed deer O. v. idahoensis – white-tailed deer O. v. leucurus – Columbian white-tailed deer O. v. macrourus – Kansas white-tailed deer O. v. mcilhennyi – Avery Island white-tailed deer O. v. mexicanus – Mexican white-tailed deer O. v. miquihuanensis – Miquihuan white-tailed deer O. v. nelsoni – Chiapas white-tailed deer O. v. nigribarbis – Blackbeard Island white-tailed deer O. v. oaxacensis – Oaxaca white-tailed deer O. v. ochrourus – northwestern white-tailed deer or northern Rocky Mountains white-tailed deer O. v. osceola – Florida coastal white-tailed deer O. v. rothschildi – Coiba Island white-tailed deer O. v. seminolus – Florida white-tailed deer O. v. sinaloae – Sinaloa white-tailed deer O. v. taurinsulae – Bulls Island white-tailed deer O. v. texanus – Texas white-tailed deer O. v. thomasi – Mexican lowland white-tailed deer O. v. toltecus – rain forest white-tailed deer O. v. truei – Central American white-tailed deer O. v. venatorius – Hunting Island white-tailed deer O. v. veraecrucis – northern Veracruz white-tailed deer O. v. virginianus – Virginia white-tailed deer or southern white-tailed deer O. v. yucatanensis – Yucatán white-tailed deer O. v. cariacou – O. v. curassavicus
Canals, or navigations, are human-made channels, or artificial waterways, for water conveyance, or to service water transport vehicles. In most cases, the engineered works will have a series of dams and locks that create reservoirs of low speed current flow; these reservoirs are referred to as slack water levels just called levels. A canal is known as a navigation when it parallels a river and shares part of its waters and drainage basin, leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley. In contrast, a canal cuts across a drainage divide atop a ridge requiring an external water source above the highest elevation. Many canals have been built at elevations towering over valleys and other water ways crossing far below. Canals with sources of water at a higher level can deliver water to a destination such as a city where water is needed; the Roman Empire's aqueducts were such water supply canals. A navigation is a series of channels that run parallel to the valley and stream bed of an unimproved river.
A navigation always shares the drainage basin of the river. A vessel uses the calm parts of the river itself as well as improvements, traversing the same changes in height. A true canal is a channel that cuts across a drainage divide, making a navigable channel connecting two different drainage basins. Most commercially important canals of the first half of the 19th century were a little of each, using rivers in long stretches, divide crossing canals in others; this is true for many canals still in use. Both navigations and canals use engineered structures to improve navigation: weirs and dams to raise river water levels to usable depths. Since they cut across drainage divides, canals are more difficult to construct and need additional improvements, like viaducts and aqueducts to bridge waters over streams and roads, ways to keep water in the channel. There are two broad types of canal: Waterways: canals and navigations used for carrying vessels transporting goods and people; these can be subdivided into two kinds:Those connecting existing lakes, other canals or seas and oceans.
Those connected in a city network: such as the Canal Grande and others of Venice Italy. Aqueducts: water supply canals that are used for the conveyance and delivery of potable water for human consumption, municipal uses, hydro power canals and agriculture irrigation. Canals were of immense importance to commerce and the development and vitality of a civilization. In 1855 the Lehigh Canal carried over 1.2 million tons of anthracite coal. The few canals still in operation in our modern age are a fraction of the numbers that once fueled and enabled economic growth, indeed were a prerequisite to further urbanization and industrialization – for the movement of bulk raw materials such as coal and ores are difficult and marginally affordable without water transport; such raw materials fueled the industrial developments and new metallurgy resulting of the spiral of increasing mechanization during 17th–20th century, leading to new research disciplines, new industries and economies of scale, raising the standard of living for any industrialized society.
The surviving canals, including most ship canals, today service bulk cargo and large ship transportation industries, whereas the once critical smaller inland waterways conceived and engineered as boat and barge canals have been supplanted and filled in, abandoned and left to deteriorate, or kept in service and staffed by state employees, where dams and locks are maintained for flood control or pleasure boating. Their replacement was gradual, beginning first in the United States in the mid-1850s where canal shipping was first augmented by began being replaced by using much faster, less geographically constrained & limited, cheaper to maintain railways. By the early 1880s, canals which had little ability to economically compete with rail transport, were off the map. In the next couple of decades, coal was diminished as the heating fuel of choice by oil, growth of coal shipments leveled off. After World War I when motor-trucks came into their own, the last small U. S. barge canals saw a steady decline in cargo ton-miles alongside many railways, the flexibility and steep slope climbing capability of lorries taking over cargo hauling as road networks were improved, which had the freedom to make deliveries well away from rail lined road beds or ditches in the dirt which couldn't operate in the winter.
Canals are built in one of three ways, or a combination of the three, depending on available water and available path: Human made streamsA canal can be created where no stream presently exists. Either the body of the canal is dug or the sides of the canal are created by making dykes or levees by piling dirt, concrete or other building materials; the finished shape of the canal as seen in cross section is known as the canal prism. The water for the canal must be provided like streams or reservoirs. Where the new waterway must change elevation engineering works like locks, lifts or elevators are constructed to raise and lower vessels. Examples include canals that connect valleys over a higher body of land, like Canal du Midi, Canal de Briare and the Panama Canal. A canal can be constructed by dredging a channel in the bottom of an existing lake; when the channel is complete, the lake is drained and the channel becom
An estuary is a enclosed coastal body of brackish water with one or more rivers or streams flowing into it, with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments, they are subject both to marine influences—such as tides and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment. The mixing of sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000–12,000 years ago. Estuaries are classified according to their geomorphological features or to water-circulation patterns, they can have many different names, such as bays, lagoons, inlets, or sounds, although some of these water bodies do not meet the above definition of an estuary and may be saline.
The banks of many estuaries are amongst the most populated areas of the world, with about 60% of the world's population living along estuaries and the coast. As a result, many estuaries suffer degradation from a variety of factors including: sedimentation from soil erosion from deforestation and other poor farming practices; the word "estuary" is derived from the Latin word aestuarium meaning tidal inlet of the sea, which in itself is derived from the term aestus, meaning tide. There have been many definitions proposed to describe an estuary; the most accepted definition is: "a semi-enclosed coastal body of water, which has a free connection with the open sea, within which sea water is measurably diluted with freshwater derived from land drainage". However, this definition excludes a number of coastal water bodies such as coastal lagoons and brackish seas. A more comprehensive definition of an estuary is "a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff.
This broad definition includes fjords, river mouths, tidal creeks. An estuary is a dynamic ecosystem having a connection to the open sea through which the sea water enters with the rhythm of the tides; the sea water entering the estuary streams. The pattern of dilution varies between different estuaries and depends on the volume of fresh water, the tidal range, the extent of evaporation of the water in the estuary. Drowned river valleys are known as coastal plain estuaries. In places where the sea level is rising relative to the land, sea water progressively penetrates into river valleys and the topography of the estuary remains similar to that of a river valley; this is the most common type of estuary in temperate climates. Well-studied estuaries include the Severn Estuary in the United Kingdom and the Ems Dollard along the Dutch-German border; the width-to-depth ratio of these estuaries is large, appearing wedge-shaped in the inner part and broadening and deepening seaward. Water depths exceed 30 m.
Examples of this type of estuary in the U. S. are the Hudson River, Chesapeake Bay, Delaware Bay along the Mid-Atlantic coast, Galveston Bay and Tampa Bay along the Gulf Coast. Bar-built estuaries are found in place where the deposition of sediment has kept pace with rising sea level so that the estuaries are shallow and separated from the sea by sand spits or barrier islands, they are common in tropical and subtropical locations. These estuaries are semi-isolated from ocean waters by barrier beaches. Formation of barrier beaches encloses the estuary, with only narrow inlets allowing contact with the ocean waters. Bar-built estuaries develop on sloping plains located along tectonically stable edges of continents and marginal sea coasts, they are extensive along the Atlantic and Gulf coasts of the U. S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 m. The barrier beaches that enclose bar-built estuaries have been developed in several ways: building up of offshore bars by wave action, in which sand from the sea floor is deposited in elongated bars parallel to the shoreline, reworking of sediment discharge from rivers by wave and wind action into beaches, overwash flats, dunes, engulfment of mainland beach ridges due to sea level rise and resulting in the breaching of the ridges and flooding of the coastal lowlands, forming shallow lagoons, elongation of barrier spits from the erosion of headlands due to the action of longshore currents, with the spits growing in the direction of the littoral drift.
Barrier beaches form in shallow water and are parallel to the shoreline, resulting in long, narrow estuaries. The average water depth is less than 5 m, exceeds 10 m. Examples of bar-built estuaries are Barnegat Bay, New Jersey. Fjords were formed where pleistocene glaciers deepened and widened existing river valleys so that they become U-shaped in cross s