But if the number of different species in that category is in the billions, it may be necessary to use a different classification scheme: "This number is very

But if the number of different species in that category is in the billions, it may be necessary to use a different classification scheme: "This number is very difficult to assess, but the discussed range varies from tens of thousands to billions;[48][49][50][51] most recent approaches and studies appear to favor the larger magnitude number" https://en.wikipedia.org/wiki/Species https://en.wikipedia.org/wiki/Species