The pentadactyl limb is found in many amphibians, reptiles, birds
and mammals. It is a limb with five digits, penta meaning five, dactyl meaning
digits. The evolution of this limb is proof that the species within the
categories mentioned with the limb all derived from a common ancestor. The bone
structure of the pentadactyl limb is very similar in many species, but it had
evolved in many different ways allowing the animal to adapt to their
environment in order to increase the chance of survival. Charles Darwin touched
upon this theory in his research, stating that it was curious that a horse’s
leg or a bat wing could have bone structures that are similar yet the animal
itself be so different.
and mammals. It is a limb with five digits, penta meaning five, dactyl meaning
digits. The evolution of this limb is proof that the species within the
categories mentioned with the limb all derived from a common ancestor. The bone
structure of the pentadactyl limb is very similar in many species, but it had
evolved in many different ways allowing the animal to adapt to their
environment in order to increase the chance of survival. Charles Darwin touched
upon this theory in his research, stating that it was curious that a horse’s
leg or a bat wing could have bone structures that are similar yet the animal
itself be so different.
The Horse Leg
The horse’s leg is a perfect example of the evolution of the
pentadactyl limb. The earliest ancestors of the horse are known to have had
three digits for their feet, which is assumed to be a development of the
pentadactyl limb. The evidence to support this has been shown through the
evolution of the horse’s leg. The
horse we know today has a leg structured of a distal phalanx, and a hoof. The
distal phalanx is part of the pentadactyl limb in most mammals. This is because
over millions of years the horse’s middle toe has evolved to become larger and
larger and the other digits of the pentadactyl limb have regressed and almost
disappeared, until just one large digit remained, which is what we wee in
modern horses today. Over millions of years the horse had become larger in size.
One reason why the limb has had to evolve is due to its weight bearing ability,
one large surface area spreads the weight of the horse more evenly and also
relieves pressure in joints. This would make the horse able to walk for longer
periods of time and also graze and eat for longer too ad the pressure on their
joints would decrease. Horses would be on their feet most of the day, therefore
one hoof would be better at shock absorbing than 5 joints, as it is much
stronger and there would be less chance of broken bones. Broken bones in the
limb of the foot could mean death for the horse, as it would not be able to run
away from predators as easily so the chances of survival are slimmer. The whole
idea of evolution is to adapt to survive, which is exactly what the legs of the
horse have shown over time. There are many reasons as to why the horse leg has
evolved, including change in diet, going from browsers to grazers, which are
constantly eating off the floor therefore needing more pressure distribution as
the horse would be bending/facing down a lot. Also to avoid predators the horse
would have had to live in environments such as rainforests and also the open
planes of America.
pentadactyl limb. The earliest ancestors of the horse are known to have had
three digits for their feet, which is assumed to be a development of the
pentadactyl limb. The evidence to support this has been shown through the
evolution of the horse’s leg. The
horse we know today has a leg structured of a distal phalanx, and a hoof. The
distal phalanx is part of the pentadactyl limb in most mammals. This is because
over millions of years the horse’s middle toe has evolved to become larger and
larger and the other digits of the pentadactyl limb have regressed and almost
disappeared, until just one large digit remained, which is what we wee in
modern horses today. Over millions of years the horse had become larger in size.
One reason why the limb has had to evolve is due to its weight bearing ability,
one large surface area spreads the weight of the horse more evenly and also
relieves pressure in joints. This would make the horse able to walk for longer
periods of time and also graze and eat for longer too ad the pressure on their
joints would decrease. Horses would be on their feet most of the day, therefore
one hoof would be better at shock absorbing than 5 joints, as it is much
stronger and there would be less chance of broken bones. Broken bones in the
limb of the foot could mean death for the horse, as it would not be able to run
away from predators as easily so the chances of survival are slimmer. The whole
idea of evolution is to adapt to survive, which is exactly what the legs of the
horse have shown over time. There are many reasons as to why the horse leg has
evolved, including change in diet, going from browsers to grazers, which are
constantly eating off the floor therefore needing more pressure distribution as
the horse would be bending/facing down a lot. Also to avoid predators the horse
would have had to live in environments such as rainforests and also the open
planes of America.
The Bat Wing
The bat’s wing shows one of the most significant evolutionary
changes of the pentadactyl limb. The limb has developed to have much longer
digits that are spread across the entire front of the wing in even intervals.
The bat was first a gliding animal, with one bone structure along the wing, the
arm, and small digits extending. The bat just had a flap of skin to help it
glide from tree to tree in search of food. Over millions of years the
pentadactyl limb of the bat has evolved to have much longer digits in order to
provide rigidity, strength and endurance enabling the bat to fly and not just
glide. The bat needed to evolve like this in order to survive due to its
environment, only being able to glide small distances with no real means of
climbing or walking would make it difficult to find food. Finding a mate to
reproduce with would also prove difficult, not to mention the avoidance of
predators. One of the five limbs has evolved to be almost like a thumb, clawed
and curved. This is to aid the bat in climbing, walking and catching and eating
prey. The digits have also evolved to be evenly spaced out in order to support
the skin and keep it taught when extended in order to help with flight. Over
the millions of years the bat’s wing had been evolving, the environment will
have been constantly changing, for example trees becoming more sparse
therefore needing to glide/fly further. Also the number of predators may have
increased meaning the bat may need to make a quicker getaway and stay out of
reach by means of flight in order to survive. A lack of food could also be a
cause of the evolutionary change, making the bat able to fly further in search
of food.
changes of the pentadactyl limb. The limb has developed to have much longer
digits that are spread across the entire front of the wing in even intervals.
The bat was first a gliding animal, with one bone structure along the wing, the
arm, and small digits extending. The bat just had a flap of skin to help it
glide from tree to tree in search of food. Over millions of years the
pentadactyl limb of the bat has evolved to have much longer digits in order to
provide rigidity, strength and endurance enabling the bat to fly and not just
glide. The bat needed to evolve like this in order to survive due to its
environment, only being able to glide small distances with no real means of
climbing or walking would make it difficult to find food. Finding a mate to
reproduce with would also prove difficult, not to mention the avoidance of
predators. One of the five limbs has evolved to be almost like a thumb, clawed
and curved. This is to aid the bat in climbing, walking and catching and eating
prey. The digits have also evolved to be evenly spaced out in order to support
the skin and keep it taught when extended in order to help with flight. Over
the millions of years the bat’s wing had been evolving, the environment will
have been constantly changing, for example trees becoming more sparse
therefore needing to glide/fly further. Also the number of predators may have
increased meaning the bat may need to make a quicker getaway and stay out of
reach by means of flight in order to survive. A lack of food could also be a
cause of the evolutionary change, making the bat able to fly further in search
of food.