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How do size and surface area affect gas exchange and tempera

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ellie williams

on 28 January 2014

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Transcript of How do size and surface area affect gas exchange and tempera

Elephants have no pleural cavity, and so the
lungs are attached directly to the chest cavity and the diaphragm. therefore inflation of the lungs is dependent on muscles in the chest, not a negative pressure.
In a snake, the respiratory system
is similar to a mammal, but snakes
breath by contracting muscles between their ribs. When eating large prey, they can protrude their glottis out the side of their mouth so that they can breathe while eating.
Gas exchange in starfish occurs over their surface: they have neither gills nor lungs.
Folds of skin on their surface permit gas exchange, also, they have a water-based vascular system, which also performs gas exchange.
In conclusion, the rate of exchange of
substances greatly depends on the size of the
animal, and then consequently the surface area to volume ratio, because as an animal gets larger, the volume increases much more than the surface area. This will affect the way in which an animal exchanges gases; smaller animals can do so mainly via diffusion, whereas larger animals need to rely on respiratory organs.
Size and surface area are also very important when regulating body temperature because smaller animals gain heat easier, but also lose heat easier. Larger animals gain heat more slowly, but also lose heat more slowly as well. There's advantages and disadvantages to both, for example small animals wont overheat whereas in colder conditions larger animals will
retain the heat they have for longer. The
larger the surface area to volume ratio,
the easier to regulate.
Image by Tom Mooring
How do size and surface area affect gas exchange and temperature control?
Temperature control
Starfish are cold-blooded animals and so they have to regulate their body temperature behaviorally -going to areas where the temperature fits their biochemical needs, e.g. rocks in shallow water will be warmer than in deeper water. A smaller starfish would regulate temperature easier because it would have a smaller surface area to volume ratio,
meaning when too hot or cold it can gain
or lose heat when necessary, easier
than larger cold-blooded
Gas Exchange
Because of the way an elephant ventilates, if any pressure or restraint was placed upon the movement of the chest or diaphragm, and so it would result in the elephant suffocating from its own weight. An elephant has a small surface area to volume ratio and so gas exchange can't occur by diffusion across the body surface, it has to occur via respiratory organs, in the same way as humans.
Temperature control
Elephants have a very hard time regulating their temperature because in proportion to their mass, they have very little skin. In order to stay cool, elephants try to expose as much skin to the air as possible, even the soles of their feet. Because they're so enormous and have such a small surface area in comparison to their mass, they have to regularly bathe in mud to coat their skin and keep them cool. They also have huge ears to try and lose heat through, because the rest of their body is coated in very thick skin, that is very difficult to lose heat through. Their ears are just a thin layer of skin coating a vast network of blood vessels, and so when they flap their ears, they're trying to create a breeze to cool the blood vessels, so the cooler blood
can be moved around their bodies.
Gas Exchange
All reptiles exchange vital gases between their bloodstream and the atmosphere primarily through lungs inside their body, rather than through gills or their skin like some animals. Although snakes have a relatively large surface area to volume ratio they cannot primarily exchange gases through the surface of their skin because it is too thick and scaly.
Temperature control
Snakes are cold-blooded animals and therefore
can't regulate their own temperature, nor do they
have a constant body temperature they need to be at like humans do. They're simply the same temperature as their surroundings and so in order to be active, snakes need to be warm, which is why they're often exposing themselves to the sun to try and warm up. This is why a larger surface area to volume ratio is needed, because they need as much of their skin
to warm as possible, but also want to need
to heat as little body mass as possible to
make the process quicker.
Gas Exchange
Starfish use the bumps and spines on their surface for gas exchange so the oxygen from the water can diffuse through, therefore because Starfish have a large surface area to volume ratio, this means that more oxygen can diffuse through their skin quicker, supplying a sufficient amount. If they didn't have a small mass in comparison to their surface area, then they wouldn't get enough oxygen to survive this way.
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