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Whales are fully aquatic, open-ocean animals: they can feed, mate, give birth, suckle and raise their young at sea. Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 29.9 metres (98 ft) and 190 tonnes (210 short tons) blue whale, which is the
A humpback whale (Megaptera novaeangliae) A leopard seal (Hydrurga leptonyx). Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans (whales, dolphins and porpoises), pinnipeds (seals, sea lions and walruses), sirenians (manatees and dugongs), sea otters and polar bears.
Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. [4] Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh and saline ...
Sperm whales have the largest brain mass of any animal on Earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males. [24] The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. [25] In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. [citation needed]
Estuaries occur where there is a noticeable change in salinity between saltwater and freshwater sources. This is typically found where rivers meet the ocean or sea. The wildlife found within estuaries is unique as the water in these areas is brackish - a mix of freshwater flowing to the ocean and salty seawater. [20]
Although there are freshwater species, the great majority are marine (salt water) species, ranging from tidal zones to depths exceeding 8,800 m (5.5 mi). Some sponges live to great ages; there is evidence of the deep-sea glass sponge Monorhaphis chuni living about 11,000 years. [213] [214]
Life histories connect disparate ecosystems; species that live at the surface during one life history stage may occupy the deep sea, benthos, reefs, or freshwater ecosystems during another. A diversity of fish species utilize the ocean's surface, [119] either as adults or as nursery habitat for eggs and young. In contrast, species floating on ...
The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale.Reaching a maximum confirmed length of 29.9 m (98 ft) and weighing up to 199 t (196 long tons; 219 short tons), it is the largest animal known ever to have existed.