What is a real situation where a high surface area to volume ratio allows an organism to survive?

Answer 1

Lots of things!

In biological terms:

The surface area to volume ratio in living organisms is very important. Nutrients and oxygen need to diffuse through the cell membrane and into the cells. Most cells are no longer than 1mm in diameter because small cells enable nutrients and oxygen to diffuse into the cell quickly and allow waste to diffuse out of the cell quickly. If the cells were any bigger than this then it would take too long for the nutrients and oxygen to diffuse into the cell so the cell would probably not survive. Single celled organisms can survive as they have a large enough surface area to allow all the oxygen and nutrients they need to diffuse through. Larger multi celled organisms need specialist organs to respire such as lungs or gills. For a single-celled organism (or a cell in a multicellular organism's body, for that matter), the surface is a critical interface between the organism/cell and its environment. Exchange of materials often occurs through the process of diffusion. This type of exchange is a passive process, and as a result imposes constraints upon the size of a single-celled organism or cell. Materials must be able to reach all parts of a cell quickly, and when volume is too large relative to surface area, diffusion cannot occur at sufficiently high rates to ensure this.

Large multi-cellular organisms, such as humans, animals etc require exchange surfaces with high SA:V ratios. The lungs are adapted to give a large SA:V ratio for the transfer of gases into and out of the blood stream. The lungs have numerous internal branches (bronchioles) that form alveoli. Alveoli are the location of gaseous exchange.

Physics: Materials with high surface area to volume ratio (e.g., very small diameter, or very porous or otherwise not compact) react at much faster rates than monolithic materials, because more surface is available to react. Examples include grain dust; while grain isn't typically flammable, grain dust is explosive. Finely ground salt dissolves much more quickly than coarse salt.

Answer 2

While the list is extensive, the first example to come 'to mind' are the Lungs.