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The pentadactyl limb
A limb with five digits, such as a human hand or foot, which is found in many amphibians, reptiles, birds, and animals, which can allow us to deduce that all species in these categories derived from one common ancestor
Vertebrates
Animals with backbones
Similar bone structure
Many vertebrates have similar bone structures despite their limbs looking very different on the outside
Pentadactyl meaning
Five-fingered
Common ancestor
An ancestral species from which later species evolved
Examples of pentadactyl organisms
Crocodiles, birds, whales, horses, bats and humans
Pentadactyl misconception
Some people assume all organisms with pentadactyl limbs must have five digits, this is not the case as some organisms such as birds have fused their digits as an evolutionary adaptation to aid flight
Evidence for evolution
As organisms share this common structural design it seems likely they share an ancestry, rather than independently developing them multiple times
Success of pentadactyl organisms
Most (or possibly all) terrestrial vertebrates have basic or modified pentadactyl limbs, this suggest the structure was very successful and helped individuals survive and reproduce, meaning most populations would end up with five-digit organisms
Theory of evolution
States that populations of organisms change and develop over time to adapt and increase their rate of survival, individuals that are better adapted are more likely to survive and pass on their useful characteristics
Horse evolution
The fossil record shows many ancestral horse species and how these species have changed over time, for example the organisms have developed longer legs and the separate toes of the ancestral horses fused to form hooves
Eohippus
Was the earliest known relative of the modern horse, looked very different to the modern horse due to separate digits and rodent-like proportions