The sentence from the selection “Tiptoeing Scientists” that is related to the idea of undiscovered species is:
"In spite of the countless challenges, new tiny frogs are being found among the planet’s habitats that have previously been understudied." (paragraph 5)
This sentence highlights the ongoing discovery of new species in areas that have not been thoroughly explored, which aligns with the idea of there being many more undiscovered species, as mentioned in the "A Ghostly New Creature" selection.