It's impossible to give a precise number of identified organisms because the number is constantly changing! Here's why:

* New discoveries: Scientists are constantly discovering new species, especially in remote areas and in microscopic life forms.

* Reclassifications: As we learn more about organisms, sometimes they are reclassified, moving them from one group to another.

* Difficult to define a "species": Defining what constitutes a distinct species can be challenging, especially for microorganisms.

Estimates:

* Known species: Scientists estimate that we have described and named around 1.8 million species of plants, animals, fungi, and microbes.

* Estimated total species: Estimates of the total number of species on Earth vary widely, but some scientists believe it could be anywhere from 5 to 100 million.

So, we know a lot, but we still have a lot to learn!