THE OCEAN DEEP

Earth Day, celebrated in the US on April 22, is a day designed to inspire awareness and appreciation for the Earth's environment. It was founded by U.S. Senator Gaylord Nelson as an environmental teach-in in 1970 and is celebrated in many countries every year. This date is Spring in the Northern Hemisphere and Autumn in the Southern Hemisphere. The United Nations celebrates an Earth Day each year on the March equinox, which is often March 20, a tradition which was founded by peace activist John McConnell in 1969. In September 1969 at a conference in Seattle, Washington, U.S. Senator Gaylord Nelson of Wisconsin announced that in spring 1970 there would be a nationwide grassroots demonstration on the environment. This occurred during a time of great concern about overpopulation and when there was a strong movement towards "Zero Population Growth." Nelson viewed the stabilization of the nation's population as an important aspect of environmentalism and later said: "The bigger the population gets, the more serious the problems become ... We have to address the population issue. The United Kingdom, with the U.S. supporting it, took the position in Cairo in 1994 that every country was responsible for stabilizing its own population. It can be done. But in this country, it's phony to say 'I'm for the environment but not for limiting immigration.'" Senator Nelson first proposed the nationwide environmental protest to thrust the environment onto the national agenda.” "It was a gamble," he recalls, "but it worked." Five months before the first April 22 Earth Day, on Sunday, November 30, 1969, The New York Times carried a lengthy article by Gladwin Hill reporting on the rising hysteria of "global cooling".[citation needed]. "Rising concern about the environmental crisis is sweeping the nation's campuses with an intensity that may be on its way to eclipsing student discontent over the war in Vietnam...a national day of observance of environmental problems...is being planned for next spring...when a nationwide environmental 'teach-in'...coordinated from the office of Senator Gaylord Nelson is planned...." Senator Nelson also hired Denis Hayes as the coordinator. April 22, 1970, Earth Day marks the beginning of the modern environmental movement. Approximately 20 million Americans participated, with a goal of a healthy, sustainable environment. Denis Hayes, the national coordinator, and his old staff organized massive coast-to-coast rallies. Thousands of colleges and universities organized protests against the deterioration of the environment. Groups that had been fighting against oil spills, polluting factories and power plants, raw sewage, toxic dumps, pesticides, freeways, the loss of wilderness, and the extinction of wildlife suddenly realized they shared common values. Mobilizing 200 million people in 141 countries and lifting the status of environmental issues onto the world stage, Earth Day on April 22 in 1990 gave a huge boost to recycling efforts worldwide and helped pave the way for the 1992 United Nations Earth Summit in Rio de Janeiro. As the millennium approached, Hayes agreed to spearhead another campaign, this time focused on global warming and a push for clean energy. The April 22 Earth Day in 2000 combined the big-picture feistiness of the first Earth Day with the international grassroots activism of Earth Day 1990. For 2000, Earth Day had the Internet to help link activists around the world. By the time April 22 came around, 5,000 environmental groups around the world were on board, reaching out to hundreds of millions of people in a record 184 countries. Events varied: A talking drum chain traveled from village to village in Gabon, Africa, for example, while hundreds of thousands of people gathered on the National Mall in Washington, D.C., USA. Earth Day 2000 sent the message loud and clear that citizens the world 'round wanted quick and decisive action on clean energy. Earth Day 2007 was one of the largest Earth Days to date, with an estimated billion people participating in the activities in thousands of places like Kiev, Ukraine; Caracas, Venezuela; Tuvalu; Manila, Philippines; Togo; Madrid, Spain; London; and New York. Founded by the organizers of the first April 22 Earth Day in 1970, Earth Day Network promotes environmental citizenship and year round progressive action worldwide. Earth Day Network is a driving force steering environmental awareness around the world. Through Earth Day Network, activists connect change in local, national, and global policies. Earth Day Network’s international network reaches over 17,000 organizations in 174 countries, while the domestic program engages 5,000 groups and over 25,000 educators coordinating millions of community development and environmental protection activities throughout the year. Earth Day is the only event celebrated simultaneously around the globe by people of all backgrounds, faiths and nationalities. More than a half billion people participate in Earth Day Network campaigns every year.

The bull shark, Carcharhinus leucas, is the best known of several species that swim in both seawater and freshwater, as well as in deltas.[2]
SKELETON
The skeleton of a shark is very different from that of bony fish and terrestrial vertebrates. Sharks and other cartilaginous fish (skates and rays) have skeletons made from cartilage, which is a flexible and dense connective tissue, but they are still considered bones. They function in the same way as human bones do. Like its relatives, rays and skates, the shark's jaw is not attached to the cranium. The jaw's surface, like its vertebrae and gill arches, is a skeletal element that needs extra support due to its heavier exposure to physical stress and its need for extra strength. It has therefore a layer of unique and tiny hexagonal plates called "tesserae", crystal blocks of calcium salts arranged as a mosaic.[3] This gives these areas much of the same strength found in real and much heavier bony tissue.
Generally there is only one layer of tesserae in sharks, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have been found to be covered with two to three layers or more, depending on the body size. The jaws of a large white shark may even have up to five layers.
In the rostrum (snout), the cartilage can be spongy and flexible to absorb the power of impacts.
The fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers.
RESPIRATION
Like other fish, sharks extract oxygen from seawater as it passes over their gills. Shark gill slits are not covered like other fish, but are in a row behind its head. A modified slit called a spiracle is located just behind the eye; the spiracle assists the water intake during respiration and even plays a major role in bottom dwelling sharks, but is also reduced or missing in active pelagic sharks.[4] While moving, water passes through the mouth of the shark and over the gills — this process is known as "ram ventilation". While at rest, most sharks pump water over their gills to ensure a constant supply of oxygenated water. A small subset of shark species that spend their life constantly swimming, a behaviour common in pelagic sharks, have lost the ability to pump water through their gills. These species are obligate ram ventilators and would presumably asphyxiate if unable to stay in motion. (Obligate ram ventilation is also true of some pelagic bony fish species.)[5]
The respiration and circulation process begins when deoxygenated blood travels to the shark's two-chambered heart. Here the blood is pumped to the shark's gills via the ventral aorta artery where it branches off into afferent brachial arteries. Reoxygenation takes place in the gills and the reoxygenated blood flows into the efferent brachial arteries, which come together to form the dorsal aorta. The blood flows from the dorsal aorta throughout the body. The deoxygenated blood from the body then flows through the posterior cardinal veins and enters the posterior cardinal sinuses. From there blood enters the ventricle of the heart and the cycle repeats.
HABITAT
Sharks are found all around the globe from the north to the south in all seas, they generally do not live in freshwater except for a few exceptions like the bull shark and the river sharks which can swim both in seawater and freshwater. Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft). The deepest confirmed report of a shark is a Portuguese dogfish that was found at 3,700 metres (12,000 ft).