Why is it that arctic animals are larger than their southern counterparts (e.g. Polar bears vs. black bears)?

Question

I believe it has something to do with surface area/volume ratio of their cells, but some other factors may determine this as well.

You are all correct...it has to do with the surface area/volume ratios of the entire organism, not just its cells. But for the last person who said grizzly bears are bigger than polar bears, you are wrong.

I'm just curious as to how the size difference relates to their surface area/volume ratio.

Answer 1

It has nothing to do with surface area/volume ratio of their cells. Surface area/volume ratio is only a factor when you are talking about single cell species. In multi-cell species, such as bears, humans, ants, elephants, trees,...... it is the number of the cells that determine their size: a baby has a smaller size than an adult human because he has fewer cells not because his cells are smaller than an adult.
In case of polar bear vs. black bears size, other than the number of the cells, the amount of fat they have reserved in their body is another factor.

Answer 2

Not all polar animals are larger than their non-polar counterparts. It depends on the animal, but you are referring to the surface area to volume ratio of the animal,not the cells, which is why marine mammals are so large. The larger you get, the less surface area you have to your internal size, so you have less area to loose heat over while having more mass to generate heat, thus staying warmer in cold environments. Smaller animals have a smaller surface area to volume ratio so have a larger area to loose heat over and less mass to create heat, thus wind up having to work harder to stay warm. There are constraints in how big you can be and what you need to be that big which is why there are still small polar animals. It wouldnt make much sense for a vole to be large, as if they were to big, they wouldnt be able to move as fast and would be eaten, so they have a thick fur coat. A blubber layer also helps in the north, insulating from heat loss. But the size is basically the SA/Volume ratio. Some people also think that it is food storage. Food supplies in the polar regions tend to be boom or bust where there is either a lot of food or none at all, so by being big, you can eat a lot and hold onto a lot of that food in the form of fat and then just use that fat when times are lean. In warmer areas, the food supply is a bit more constant.

Answer 3

The bigger an animal is, the warmer it is inside it. If you go to the arctic, wear a big coat.

Answer 4

Grizzley Bears are not Arctic animals and they are larger
than Polar Bears...
Arctic animals are not always larger than their southern counterparts..