The Evolution of the Pentadactyl Limb
The Pentadactyl Limb shows the structure of the hand and foot. Although from the outside this looks different on every animal, studies show that this limb has evolved of many years and suggests that many animals have one common ancestor. To show this, I am going to use the bats wing and horses hoof. (M4
Adaptations of the Bat Wing
The bat wing has evolved to enable flight. In the wing of a bat, the digits have been elongated which allows them to support the wings and provide a greater surface area which allows the bat to fly. The digits are covered by the patagium. The bones that make up the pentadactyl limb are less dense which reduces the weight of them allowing flight to be possible. The 'thumb' extends out of the limb and forms a claw which enables the bat to climb. It is thought that the bat was at first a gliding mammal like the flying squirrel of today as it cannot take off from the ground. The basal metacarpal is the largest of the digits and is responsible for supporting the wing along with the three phalanges.
Over time, the humerus has been lengthened and made thinner whilst the ulna has been reduced in size and fused with the radius. These structures are also needed to support the wing. The structure is very fragile due to its low density. Bats have greater maneuverability than most flying species due to the wing being flexible.
Over time, the humerus has been lengthened and made thinner whilst the ulna has been reduced in size and fused with the radius. These structures are also needed to support the wing. The structure is very fragile due to its low density. Bats have greater maneuverability than most flying species due to the wing being flexible.
Adaptations of the Horses Hoof
The hoof of a horse has evolved to allow running. Around 65 million years ago, the ancestor of the modern horse had 4 toes on the front limbs and 3 toes on the back which gradually evolved into a one toed hoof. The hoof is supported by what was the middle toe in its ancestors. As the pentadactyl limb evolved, the middle toe gradually extended whilst the other toes reduced in size and eventually disappeared. As this happened, the hoof began to form whilst the pads of the feet became the frog on the hoof. This adaptation allowed the horse to be better suited to life on grasslands and rough terrain due to the hoof being tough. As the pentadactyl limb evolved, the horse grew larger in size and so did the legs giving a strong support. The horses ancestors were only around 50 pounds compared to the modern horse.
Video about the evolution of bats.
Video about evolution of the horse.
