As is appropriate for a banknote celebrating the life and work of a naturalist, animal and plant imagery is used throughout the note.

On the back of the note, the left-hand side is taken up with an image of a humming bird feeding on yellow blooms. The humming bird is based on the type characteristically found in the region of the Galapagos Islands, coloured in the banknote's predominant colour scheme. The flowers are shown magnified in Darwin's own lever compressor lens, now preserved at Down House, Darwin's home, highlighting the use that Darwin made of observations of living species. Immediately below the flowers is an ornamental border, based on the decoration on Darwin's own spill-holder, also kept at Down House.

Some fossil evidence was known to Darwin. An extinct type of marine creature - ammonites - are mentioned in the text of "On the Origin of Species by Means of Natural Selection". He also cited trilobites as examples of groups of creatures that had become extinct in his discussion on selective pressures. Fossil ammonites and trilobites are included in the background details on the front of the note.