Joe Hanson from It’s Okay to Be Smart shares some estimates for the total number of species on Earth and also explains how scientists came to settle on those numbers. The video pairs well with the previous episode of the series, which deals with how species are classified. How many species are there on Earth? In biology, this is one of a fundamental question that we still don’t have a very good answer for. Imagine if chemists didn’t know all the elements of the periodic table, or if physicists didn’t know all of the particles of the standard model. Knowing how many different species there are is information we need to know in order to protect the environment, but it’s a lot harder than you think!