Final answer:
Scientists estimate that there are approximately 15 million species on the planet, based on the discovery of 1.5 million species.
Step-by-step explanation:
According to recent estimates, scientists believe that there are approximately 8.7 million eukaryote species on the planet. Of these, about 1.5 million have been discovered and named. This means that scientists estimate that there are about 7.2 million eukaryote species yet to be discovered. Given that scientists have discovered 1.5 million species, which is roughly 1/10 of the total number of species, we can estimate that the total number of species is around 15 million.