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Secondary aquatic adaptations tend to develop in early speciation as the animal ventures into water in order to find available food. As successive generations spend more time in the water, natural selection causes the acquisition of more adaptations. Animals of later generations may spend most their life in the water, coming ashore for mating.
The largest living amphibian is the 1.8 m (5 ft 11 in) South China giant salamander (Andrias sligoi), but this is dwarfed by prehistoric temnospondyls such as Mastodonsaurus which could reach up to 6 m (20 ft) in length. [7] The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology.
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 ...
Besides hoarding food outside, most animals are adapted to store and carry food and energy reserves inside their bodies. All of us are probably familiar with this adaptation because we go through ...
All but one species bury in the mud when the body of water they live in dries up, surviving up to two years until water returns. Bichir (Polypteridae): These 12 species are the only ray-finned fish to retain lungs. They are facultative air breathers, requiring access to surface air to breathe in poorly oxygenated water. [1]
Surface-living animals (such as sea otters) need the opposite, and free-swimming animals living in open waters (such as dolphins) need to be neutrally buoyant in order to be able to swim up and down the water column. Typically, thick and dense bone is found in bottom feeders and low bone density is associated with mammals living in deep water.
This change from a body plan for breathing and navigating in gravity-neutral water to a body plan with mechanisms enabling the animal to breath in air without dehydrating and move on land is one of the most profound evolutionary changes known. [18] [19] Tetrapods can be divided into four classes: amphibians, reptiles, birds and mammals.
Wading and bottom-feeding animals (e.g. moose and manatee) need to be heavier than water in order to keep contact with the floor or to stay submerged, surface-living animals (e.g. otters) need the opposite, and free-swimming animals living in open waters (e.g. dolphins) need to be neutrally buoyant in order to be able to swim up and down the ...