Final answer:
A polar bear's large and rotund shape most closely conforms to a sphere, which is beneficial for retaining heat in Arctic environments. Their white fur also serves as camouflage, aiding in hunting and survival.
Step-by-step explanation:
The shape of a polar bear, described as very large and rotund, best conforms to the shape of a sphere. When we consider figures that have a volume, a sphere is the shape that has the smallest surface area relative to its volume. This feature is significant in biological terms because such a shape helps minimize heat loss in cold environments. Polar bears, living in regions covered by ice, have evolved with features like thick fur and a dense layer of fat under their skin, known as blubber, to generate and retain heat effectively, which is similarly advantageous as having a spherical shape.
Polar bears' white fur serves as camouflage in the snowy, icy Arctic biome, allowing them to blend in with their surroundings while hunting seals and evading predators. This adaptation, along with their round body shape, is crucial for their survival in such a harsh and cold ecosystem.