The pentadactyl limb

Paper 1

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