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  • Marine life

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    General characteristics of a large marine ecosystem (Gulf of Alaska) Killer whales (orca) are marine apex predators. They hunt practically anything, including tuna, smaller sharks and seals. However, the oceans are alive with less obvious, but equally important forms of marine life, such as bacteria.Marine life, or sea life or ocean life, is the plants, animals and other organisms that live in the salt water of the sea or ocean, or the brackish water of coastal estuaries. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms produce much of the oxygen we breathe. Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land. Most life forms evolved initially in marine habitats. Oceans provide about 99 percent of the living space on the planet. The earliest vertebrates appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton, and particularly phytoplankton, are key primary producers forming the general foundation of the ocean food chain. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see insect and mollusc siphons) and gills (Carcinus). However, as invertebrate life evolved in an aquatic habitat most have little or no specialisation for respiration in water. Marine vertebrates must obtain oxygen to survive, and they do so in various ways. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Some amphibians are able to absorb oxygen through their skin. Altogether there are 230,000 documented marine species, including about 20,000 species of marine fish, and it has been estimated that nearly two million marine species are yet to be documented. Marine species range in size from the microscopic, including plankton and phytoplankton which can be as small as 0.02 micrometres, to huge cetaceans (whales, dolphins and porpoises) including the blue whale, the largest known animal reaching up to 33 metres (109 feet) in length. Marine microorganisms, including bacteria and viruses, constitute more than 90% of the total marine biomass.

  • Submarine

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    underway in Groton, Connecticut, July 2004 A submarine (or simply sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most commonly refers to a large, crewed vessel. It is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. The noun submarine evolved as a shortened form of submarine boat; by naval tradition, submarines are usually referred to as "boats" rather than as "ships", regardless of their size (boat is usually reserved for seagoing vessels of relatively small size). Although experimental submarines had been built before, submarine design took off during the 19th century, and they were adopted by several navies. Submarines were first widely used during World War I (1914–1918), and are now used in many navies large and small.

  • Hybrid vehicle

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    A hybrid vehicle uses two or more distinct types of power, such as internal combustion engine to drive an electric generator that powers an electric motor, e.g. in diesel-electric trains using diesel engines to drive an electric generator that powers an electric motor, and submarines that use diesels when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids. The basic principle with hybrid vehicles is that the different motors work better at different speeds; the electric motor is more efficient at producing torque, or turning power, and the combustion engine is better for maintaining high speed (better than typical electric motor). Switching from one to the other at the proper time while speeding up yields a win-win in terms of energy efficiency, as such that translates into greater fuel efficiency, for example.

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