evolution

[Gizelle213]

If the wheel is the most efficient form of transportation, why haven't any organisms evolved with wheels?

[incitatus]

Because of the difficulties in getting there through gradual steps. That said there are radiolarians that basically are wheels, and certainly things like armadillos use a ball shape to roll away from danger, though this may be accidental. Herodotus reported rolling snakes who grasped their tails in their mouths to form a wheel, but I dont know if there are any modern sightings of such chimerae

[Welshwizard]

There are caterpillars and lizards that curl into a circle and roll as well, I think the caterpillars are called purl caterpillars but im not sure.

[aleccawley]

As already explained, some creatures can roll themselves into a ball and roll around. However, it is difficult for a living organism to have attached wheels, like a car, because of the difficulty of getting a blood supply to the rotating part. Without a supply of blood (or equivalent) it is difficult for the wheel to develop or repair injuries. Also, wheels are not that great if you don't have roads. Many primitive cultires knew about the wheel but never used it because all that they had were muddy tracks. Even those who cycle across country have occasionally to stop and lift their bikes - an animal which had only wheels would be in create danger of geting stuck. Of course, tumbleweeds wheel across the countryside.

[babthrower]

evolution works from a platform: a pre-existing structure. A pseudopod can morph into a leg or tool to move food to the mouth; a light-sensitive spot can morph into an eye. A tubelike body can develop the musculature to move sinuously through water, increasing the organism's mobility. But a wheel is complex, as Alex explained so well. While it is not impossible for complex organs to evolve (e.g. the eye and the brain) there must be an advantage to every intermediate stage (e.g. the eye and the brain). It would seem the advantages of wheels for locomotion were not sufficiently superior to other means of locomotion to bring about this feature.