The Evolution Of The Pentadactyl Limb
The bone structure of many animals is similar however they appear different due to evolution. Most animals start off with the pentadactyl limb which is where the limb has 5 digits on the hands and feet the appearance of these limbs on animals have changed for the better. They have adapted to their surrounding environment to give them a better chance of survival. Now we shall look at the evolution of the pentadactyl limb in the horse and the whale.
The bone structure of many animals is similar however they appear different due to evolution. Most animals start off with the pentadactyl limb which is where the limb has 5 digits on the hands and feet the appearance of these limbs on animals have changed for the better. They have adapted to their surrounding environment to give them a better chance of survival. Now we shall look at the evolution of the pentadactyl limb in the horse and the whale.
Horse (Equus Ferus Caballus)
The horse now is seen to have one ‘finger’ which is split slightly, creating the hoof shape this shows the remains of a two finger structure, showing evolution has occurred to change this for the better of the animal in the environment it lives in. The evolution of the horse is as follows;
The earliest known member of the horse family was a deer like animal-Hypothermia. It was small with short legs and broad feet. Their environment and natural habitat was wooded. These small animals would live and feed in the same area. The function of the legs would be just so the animal could move about and feed. If there were predators they would be able to dodge them through openings in the vegetation. These horses had four toes on its front legs and three on its hind feet these separate toes helping to climb and run over the bumpy land without struggle.
As more open grasslands were around it was time for the Hyracotherium to evolve. The Epihippus was that evolution; it could take advantage of the open grasslands and get more food. It had longer legs giving it speed in the open and its grinding teeth could handle grass. These horses would run out into the grassland grab a lot of food and run back into the forest. Natural selection at this stage meant gradually the horse population would have longer legs. The longer legs were great for speed but it made the animal taller. It is hard for them to hide from their predators that also had moved out into the grassland. This evolution led us to Mesohippus.
This horse was slightly larger with even longer legs. The back was less arched, which gave it more speed and greater endurance at speed. This horse still lived in the forest part of the time but could now venture further out into the expanding grasslands. Some of these horses evolved by becoming larger with longer legs known as Miohippus.
The ankle joint on this horse changed slightly to make it faster in grass. They lived in the grasslands, alongside the Mesohippus who were in the forest. The habitat continued to change the forests getting smaller while the grasslands more vast. Some of these Miohippus changed from browsing to grazing taking advantage of the new grasses. This meant them spending all the time in the grasses. The environment meant these open country grass grazers could benefit from being swift runners with long legs. These animals had a slight bone change that locked the two lower leg bones together. This eliminated leg rotation but gave stronger forward-and-back strides. Another variation was to stand on tip toe (adaptation for speed). Horses with these variations survived to have children who inherited the variation. Standing on tip toe meant those with stronger toes and stronger ligaments to the toe had a better chance. The ligament to the central big toe became much thicker and became like a spring that was cocked when the foot stepped down and released to push forward. The dog like pads became a strong hoof on the middle toe; this could dig into hard ground. The other toes now no longer needed disappeared. Miohippus had one main toe hoof that bore its weight. All these changes made legs specialized for just one function: rapid running over hard ground this was due to carnivores becoming faster meaning the horse had to become faster to and adapt for survival.
The horse now is seen to have one ‘finger’ which is split slightly, creating the hoof shape this shows the remains of a two finger structure, showing evolution has occurred to change this for the better of the animal in the environment it lives in. The evolution of the horse is as follows;
The earliest known member of the horse family was a deer like animal-Hypothermia. It was small with short legs and broad feet. Their environment and natural habitat was wooded. These small animals would live and feed in the same area. The function of the legs would be just so the animal could move about and feed. If there were predators they would be able to dodge them through openings in the vegetation. These horses had four toes on its front legs and three on its hind feet these separate toes helping to climb and run over the bumpy land without struggle.
As more open grasslands were around it was time for the Hyracotherium to evolve. The Epihippus was that evolution; it could take advantage of the open grasslands and get more food. It had longer legs giving it speed in the open and its grinding teeth could handle grass. These horses would run out into the grassland grab a lot of food and run back into the forest. Natural selection at this stage meant gradually the horse population would have longer legs. The longer legs were great for speed but it made the animal taller. It is hard for them to hide from their predators that also had moved out into the grassland. This evolution led us to Mesohippus.
This horse was slightly larger with even longer legs. The back was less arched, which gave it more speed and greater endurance at speed. This horse still lived in the forest part of the time but could now venture further out into the expanding grasslands. Some of these horses evolved by becoming larger with longer legs known as Miohippus.
The ankle joint on this horse changed slightly to make it faster in grass. They lived in the grasslands, alongside the Mesohippus who were in the forest. The habitat continued to change the forests getting smaller while the grasslands more vast. Some of these Miohippus changed from browsing to grazing taking advantage of the new grasses. This meant them spending all the time in the grasses. The environment meant these open country grass grazers could benefit from being swift runners with long legs. These animals had a slight bone change that locked the two lower leg bones together. This eliminated leg rotation but gave stronger forward-and-back strides. Another variation was to stand on tip toe (adaptation for speed). Horses with these variations survived to have children who inherited the variation. Standing on tip toe meant those with stronger toes and stronger ligaments to the toe had a better chance. The ligament to the central big toe became much thicker and became like a spring that was cocked when the foot stepped down and released to push forward. The dog like pads became a strong hoof on the middle toe; this could dig into hard ground. The other toes now no longer needed disappeared. Miohippus had one main toe hoof that bore its weight. All these changes made legs specialized for just one function: rapid running over hard ground this was due to carnivores becoming faster meaning the horse had to become faster to and adapt for survival.
Whale (Orcinus Orca)
The whale today has its forelimbs (flippers) which are used for steering it has totally lost its back limbs due to them not been necessary for any specific function nowadays. Its closest living relative is the hippopotamus however these are not ancestors. The evolution of the whale is as follows;
The first whales called Pakicetus were typically land animals. They had four long dogs like legs. These are known as Pentadactyl limbs (a limb with 5 digits). So these limbs were important in its daily life for moving about the land. As it began to evolve in its habitat and environment, it had to change these limbs for its more aquatic lifestyle. Now it was known as Ambulocetus, with shorter hands and its feet enlarged like paddles. These were known as the Walking Whale and displayed some distinctly whale like characteristics. He possessed a long otter like body with webbed padded feet. He had also evolved to his new environment and spent a large amount of time in the water.
Homology is this occurrence of similar structures in different organisms because they are descended from a common ancestor by the process of evolution. The same structure can be adapted for different things. The limbs on these early whales altering so more like paddles in the water, but underneath the same structure. The Pentadacty limb is adapted for locomotion but still contains the same bone pattern.
Rodhocetus had shown a striking adaptation to its aquatic lifestyle. This prehistoric whale was amphibious crawling onto dry land to look for food and give birth.
Whale evolution is the development of large animals from smaller ones. The skeleton of today’s Whale which lives all its life in the water has shown it still has the pentadactyl limbs now used differently than the first whales. It has a collection of bones in the flippers (that closely correspond to the bones in the human arm and hand). Somewhere near the back of the whale floating in the body but not attached are a few little bones that scientists believe are what its back legs were once.
The whale today has its forelimbs (flippers) which are used for steering it has totally lost its back limbs due to them not been necessary for any specific function nowadays. Its closest living relative is the hippopotamus however these are not ancestors. The evolution of the whale is as follows;
The first whales called Pakicetus were typically land animals. They had four long dogs like legs. These are known as Pentadactyl limbs (a limb with 5 digits). So these limbs were important in its daily life for moving about the land. As it began to evolve in its habitat and environment, it had to change these limbs for its more aquatic lifestyle. Now it was known as Ambulocetus, with shorter hands and its feet enlarged like paddles. These were known as the Walking Whale and displayed some distinctly whale like characteristics. He possessed a long otter like body with webbed padded feet. He had also evolved to his new environment and spent a large amount of time in the water.
Homology is this occurrence of similar structures in different organisms because they are descended from a common ancestor by the process of evolution. The same structure can be adapted for different things. The limbs on these early whales altering so more like paddles in the water, but underneath the same structure. The Pentadacty limb is adapted for locomotion but still contains the same bone pattern.
Rodhocetus had shown a striking adaptation to its aquatic lifestyle. This prehistoric whale was amphibious crawling onto dry land to look for food and give birth.
Whale evolution is the development of large animals from smaller ones. The skeleton of today’s Whale which lives all its life in the water has shown it still has the pentadactyl limbs now used differently than the first whales. It has a collection of bones in the flippers (that closely correspond to the bones in the human arm and hand). Somewhere near the back of the whale floating in the body but not attached are a few little bones that scientists believe are what its back legs were once.