Answers (2)
Nobody actually knows. We have been trying to work this out for hundreds of years. We know that there are roughly 8.7 million species on Earth - this is an estimate and is as accurate as we can get.
The vast majority of the 8.7 million are animals. When all calculations were done the figure came out as 7.7 million animals plus or minus about a million. This is an estimate because we have not identified all different species on Earth yet. These figures indicate that we have only identified 14% of the worlds species so far.