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Because they have the dual role of producing thrust in both flight and swimming, wings in these animals demonstrate a compromise between the functional demands of two different fluid media. Because the density of water is so much higher than air, the same wing excursion in either medium will produce more thrust in water. [1]
Freshwater biology is also used to study the effects of climate change and increased human impact on both aquatic systems and wider ecosystems. [4] Freshwater organisms, vertebrates especially, appear to be at a higher extinction risk from climate change than terrestrial or marine organisms. [5]
Aquatic animals (especially freshwater animals) are often of special concern to conservationists because of the fragility of their environments. Aquatic animals are subject to pressure from overfishing/hunting, destructive fishing, water pollution, acidification, climate change and competition from invasive species.
WASHINGTON (AP) — Nearly a quarter of animals living in rivers, lakes and other freshwater sources are threatened with extinction, according to new research published Wednesday. “Huge rivers like the Amazon can appear mighty, but at the same time freshwater environments are very fragile,” said study co-author Patricia Charvet, a biologist ...
The speed of motion in air is faster than in water because of drag force. The drag force is proportional to density of the fluid. The animal jumping out of water will feel almost no drag, since the air density is 1,000 times less than water density. Usually animals gain thrust for the jumping as how they lift themselves underwater.
A 2020 study reports that by 2050 global warming could be spreading in the deep ocean seven times faster than it is now, even if emissions of greenhouse gases are cut. Warming in mesopelagic and deeper layers could have major consequences for the deep ocean food web, since ocean species will need to move to stay at survival temperatures. [69] [70]
Swimming animals that are denser than water must generate lift or adapt a benthic lifestyle. Movement of the fish to generate hydrodynamic lift is necessary to prevent sinking. Often, their bodies act as hydrofoils, a task that is more effective in flat-bodied fish. At a small tilt angle, the lift is greater for flat fish than it is for fish ...
Even using conservative estimates, freshwater fish extinction rates in North America are 877 times higher than background extinction rates (1 in 3,000,000 years). [32] Projected extinction rates for freshwater animals are around five times greater than for land animals, and are comparable to the rates for rainforest communities. [24]