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t. e. The mesopelagiczone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. [ 1 ] It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the ...
The oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf (e.g. the neritic zone), but operationally is often referred to as beginning where the water depths drop to below 200 metres (660 ft), seaward from the coast into the open ocean with its pelagic zone. It is the region of open sea beyond the edge of ...
Bivalvia. Bivalvia (/ baɪˈvælviə /) or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half- shells known as valves.
Cystonectae. Physonectae. Synonyms. Siphonophora Eschscholtz, 1829. Siphonophorae (from Greek siphōn 'tube' + pherein 'to bear' [2]) is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 species described thus far. [3]
Ocean surfaces occupy 72% of the Earth's total surface. They can be divided into surfaces of the relatively shallow and nutrient rich coastal areas above the continental shelves (light blue), and surfaces of the more expansive and relatively deeper but nutrient poor ocean that lies beyond (deep blue). External videos.
The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately 200 meters (660 ft) in depth. [1][2] From the point of view of marine biology it forms a relatively stable and well-illuminated environment for marine life, from plankton up to large fish and corals ...
The low position of its mouth suggests it foraged the ocean floor. [16] It is not known how its trunk and caudal fin looked like. [17] Astraspis: Astraspis (star shield) is an extinct genus of primitive jawless fish related to other Ordovician fishes, such as Sacabambaspis and Arandaspis. Fossils show clear evidence of a sensory structure ...
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms — aquatic life —that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. [1]