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Total species range is highly variable for marine mammal species. On average most marine mammals have ranges which are equivalent or smaller than one-fifth of the Indian Ocean . [ 33 ] The variation observed in range size is a result of the different ecological requirements of each species and their ability to cope with a broad range of ...
Marine mammals comprise over 130 living and recently extinct species in three taxonomic orders. The Society for Marine Mammalogy, an international scientific society, maintains a list of valid species and subspecies, most recently updated in October 2015. [1] This list follows the Society's taxonomy regarding and subspecies.
Marine biology studies species that live in marine habitats. Most of the Earth's surface is covered by ocean, which is the home to marine life. Oceans average nearly four kilometers in-depth and are fringed with coastlines that run for about 360,000 kilometres. [4] [5] Marine biology can be contrasted with biological oceanography.
As of 2023, more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. [2] [3] Marine life is studied scientifically in both marine biology and in biological oceanography.
General characteristics of a large marine ecosystem (Gulf of Alaska). Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, plants, algae, fungi, protists, single-celled microorganisms and associated viruses living in the saline water of marine habitats, either the sea water of marginal seas and oceans, or the brackish water of coastal ...
Human activities affect marine life and marine habitats through overfishing, habitat loss, the introduction of invasive species, ocean pollution, ocean acidification and ocean warming. These impact marine ecosystems and food webs and may result in consequences as yet unrecognised for the biodiversity and continuation of marine life forms.
Aquatic animals generally conduct gas exchange in water by extracting dissolved oxygen via specialised respiratory organs called gills, through the skin or across enteral mucosae, although some are evolved from terrestrial ancestors that re-adapted to aquatic environments (e.g. marine reptiles and marine mammals), in which case they actually ...
Currently, of the approximately 12,000 extant reptile species and sub-species, only about 100 of are classed as marine reptiles. [30] Except for some sea snakes, most extant marine reptiles are oviparous and need to return to land to lay their eggs. Apart from sea turtles, the species usually spend most of their lives on or near land rather ...