Why do elephants have big ears? (size, surface area, volume?)?

Why do elephants have big ears? Is it because of size, surface area, volume etc. please explain.


a beached whale more likelt to die by overheating than a dolphin because?


larger mammals found nearer poles than equator?


why would someone smaller be in greater danger of hypothermia? please discuss area, volume, mass etc in answers.

Why do elephants have big ears? (size, surface area, volume?)?
they have big radiators in them.(It's hooooot! in Africa.)
Reply:Elephants have big ears to help cool them.





There is greater volume per unit of surface area. It actually has more to do with the insulating effects of matter but biology types like to use the ratio of the surface area to volume.





Less surfaces area to volume so slower cooling for larger animals. I don't accept that explanation but I seem to be in the minority.





More surface area to volume.
Reply:If a scale model of you was built twice as tall as you, it would have 4 times your surface area to get rid of excess heat but 8 times the volume of muscle and brain producing heat, so large animals like elephants need ways of shedding heat that you haven't got, like large ears and panting, like dogs do, especially as many of these animals, such as jumbos, live in the tropics. A beached whale, being large, is likely to die of heart failure. Animals as large as whales need to live in the water, so buoyancy can support them. Because of the scaling thing, large animals, which produce large amounts of heat, are happier in cooler climates. Similarly small people are more likely to come down with hypothermia. People like Europeans and Inuit tend to be fatter than black people and south east Asians. Robins in Iceland are about as big as thrushes in the south of England. This scaling thing explains why no animals larger than hummingbirds can use the same method to fly, and planes can't fly like geese do, by flapping their wings. As you get bigger the lift you get goes up as the square of your length, but the weight to be lifted goes up as the cube.
Reply:All of these examples are talking about how fast or slowly something can change its temperature.





Things change temperature by giving off (or absorbing) heat through their surfaces. So the rate of temperature change is proportional to the amount of their surface area. Large surface area means more "heat units" per second can pass into or out of the environment.





But wait -- If you have a big, massive body, it's going to require more "heat units" coming in to warm you up (or, more "heat units" going out to cool you off). If something weighing 100 lbs. needs 40 heat units to warm up by 1 degree, then something weighing 200 lbs (of the same material) is going to need 80 heat units to warm up by the same 1 degree.





So, a large body mean greater surface area (faster cooling/heating); but it also means more mass (slower cooling/heating). Which effect is more important?





Well, consider the simple case of a hot cube. Say it's 1cm on a side and its mass is 1 gram. And lets say it is cooling off at the rate of 1 degree per minute.





Now take another cube of the same material, at the same temperature, but this time it is 3 cm on a side. Consider how its surface area and its mass change:





Surface area of little cube: 6 square cm


Surface area of big cube: 54 square cm


The big cube has 9 times as much surface area, so it is throwing off heat 9 times as fast.





BUT:





Mass of little cube: 1 gram


Mass of big cube: 27 grams


The big cube has 27 times as much mass, so it needs to lose 27 times as much heat in order to cool off like the little cube.





The increase in mass (slowing the cooling) overwhelms the increase in surface area (speeding the cooling), so the net effect is that the big cube does not cool off as fast as the little cube.





The general rule is: As things increase in size, their mass increases faster than their surface area. The net result is that bigger things have a harder time warming or cooling than smaller things (of the same material).