EVERYDAY SCIENCE

Detailed explanation-1: -Many vertebrates have a very similar bone structure despite their limbs looking very different on the outside. This structure is known as the pentadactyl (five fingered) limb. This suggests that many vertebrates descended from the same common ancestor.

Detailed explanation-2: -The evolutionary explanation of the pentadactyl limb is simply that all the tetrapods have descended from a common ancestor that had a pentadactyl limb and, during evolution, it has turned out to be easier to evolve variations on the five-digit theme, than to recompose the limb structure.

Detailed explanation-3: -This arrangement is known as the pentadactyl limb. Some species have subsequently fused these fingers into hooves or lost them altogether, but every mammal, bird, reptile and amphibian traces its family tree back to a pentadactyl ancestor that lived around 340 million years ago.

Detailed explanation-4: -The ancestral tetrapod pentadactyl limb plan consists of three parts: upper (arm or thigh) containing one long bone, middle (forearm or shank) containing two long bones, and lower (hand or foot) containing a number of small bones.