How many organisms are there on this planet?

In order to answer that question, we must first inspect
what we consider to be an Organism.

An Organism is a living being that is changing and evolving
through time. It responds to its environment.
It comprises of many different systems (depending on the complexity of the organism)
that work together.
Should one if the systems fail, the Organism will usually die / be permanently disabled.

By these standards, our planet, Earth, is an organism.
We are but a system inside it.
If you find this foreign or unlikely, picture the world without
Bugs, or without Plants.

Naturally the world could exist without Human Beings but I see us
as the Brain of this system, at least that’s what we use to be.
The Earth organism seems to be failing on our watch.
Our failing system is infecting other systems and killing them off
one by one, may it be the Ozone layer or the mass Extinction of animals,
we are not only failing on our own, we act as a cancerous cell.

It is impossible to shake off our responsibility as the most intelligent creature
on this planet (except the dolphins, of course), the minimum responsibility
that we have is to maintain our system and
stop killing this great organism that hosts us.