Just a parasite-predator 'taker' feeding off the hard work of humble autotrophic producers ?
Is this planet really the near-permanent home only for microbes, the bacteria above all ?
Could some casual catastrophe really kill off everything else on earth ?
Bingo : everything dead and gone.
Except for a few extremophile bacteria buried deep in the ocean mud near a volcanic vent and lying ready to re-colonize the whole world, again, when conditions improve.
Earth natural home of bacteria - or all the Universe's Life ?
Or is Earth IT , it for all life in the universe ?
It is the only begetter of all the Universe's life, from beings the size of tiny virus to giant beings like the earth's Blue Whale , and thus humanity's only home ?
We won't know anything definite until we find living beings - whether just a few tiny bacteria surviving just barely in cracks of rocks , or billions of large beings like us humans - on some other planet(s).
My own view is that Earth is an extremely rare planet.
Possibly rare to the vanishing point - at least when it comes to not merely permitting a little bit of life to cling about for a relatively period of time, but in sustaining a wide variety of abundant life forms for billions of years.
Clearly though, humans are but a single (and fairly recent) species with quite demanding biological requirements for survival and reproduction.
By contrast, the billions of years old bacteria make up one giant (and super versatile) meta-species.
HGT (their unique horizontal genetic mechanism that allows the transfer of genes between species within the vast bacteria order) helps makes them extremely resilient to a violently changing environment.
Collectively, this sharing of all of their genes between them give the whole order the ability to chose between thousands of types of 'food' (from acidic bare rock to tasty living humans) for survival.
In addition, bacteria, of course, have an incredibly tiny size and also usually lack any way (or need) to use energy moving about seeking food.
Their usual means of 'eating' being the absorbing of nearly-ready-to-use molecules by means of passive diffusion saves them lots and lots of energy.
Many can postpone reproduction for tens of thousands of years , if food is short.
(While other bacteria can double in numbers in tens of minutes - what a wide expanse of reproductive speed !)
All this means that a single living bacteria (and you only need one to reproduce) can survive for tens of thousands of years on a tiny amount of nutrients.
Nutrients that would be trillions and trillions of times too small to sustain the high daily metabolism of two living adult humans potentially able to reproduce.
The last Man on Earth will , in reality, be a bacteria
The whole surface of the Earth would have to be molten hot steel before the very last bacteria on Earth disappeared !
By contrast, just warming the Earth temperature by a mere degree or two would at least wipe out our present day human civilization.
While a single wrong finger on the Red Button would kill most humans in a few weeks , between initial blast and trickle down Fallout.
Despite all of this evidence of the tender fragility of the human species, amazingly human hubris still knows no bounds...
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