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The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. The word abyss comes from the Greek word ἄβυσσος ( ábussos ), meaning "bottomless". [ 1 ] At depths of 4,000–6,000 m (13,000–20,000 ft), [ 2 ] this zone remains in perpetual darkness.
Examination of a 9 m (30 ft) giant squid, the second largest cephalopod, that washed ashore in Norway in 1954 In zoology, deep-sea gigantism or abyssal gigantism is the tendency for species of deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range.
Pelagic zones. The ocean can be conceptualized as being divided into various zones, depending on depth, and presence or absence of sunlight.Nearly all life forms in the ocean depend on the photosynthetic activities of phytoplankton and other marine plants to convert carbon dioxide into organic carbon, which is the basic building block of organic matter.
The bathypelagic and abyssopelagic zones are aphotic, meaning that no light penetrates this area of the ocean. These zones make up about 75% of the inhabitable ocean space. [2] The epipelagic zone (0–200 metres (0–656 ft) deep) is the area where light penetrates the water and photosynthesis occurs. This is also known as the photic zone.
Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. They are unique among animals in having bilateral symmetry at the larval stage, but fivefold symmetry (pentamerism, a special type of radial symmetry) as adults. [296] Echinoderms are important both biologically and geologically.
Melanocetus murrayi was first described by the German zoologist Albert Günther in 1887 from material dredged up from the deep on the Challenger expedition of 1872 to 1876, the first scientific attempt to research the ocean depths; it was named in honour of Sir John Murray, a British biologist who took part in the expedition and was one of the founders of the new study of oceanography.
[citation needed] Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, [54] making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles).
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft).Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface.