We’re used to measuring life in organisms. And mostly, organisms are treated as natural and absolute. But are they? Can indeed biosphere be unequivocally segregated into organisms, or are they merely an imaginary thing? A habit…
A delicacy for thought 1: Every bacterial cell is an organism. Doesn’t it imply that every cell of a multicellular is an organism, rather than entire ‘body’? Every erythrocyte is quite alive and independent to certain extent. Yes, it demands perfect conditions, and it dies when taken from the blood. So chicken does: it can only survive on a small portion of Earth. It won’t tolerate Northern Pole and the Earth’s core. Let alone it won’s survive on Venus or Neptune.
A delicacy for thought 1,5: During blood transfusion, an erythrocyte is transferred into another body. Doesn’t it prove that it’s a separate organism, that can ‘walk’ between habitats? Or is it still donor’s? So donor now lives in two bodies at the same time?
A delicacy for thought 2: They say that multicellular organism is a multitude of cells that comprises a ‘body’ with defined ‘border’. But how about a tail dropped by a lizard? It’s not connected to the body anymore, is it still part of the lizard? If so, then baby jellyfish budded from parent’s body is still part of the parent’s organism, and every single jellyfish in the ocean are one organism. Lizard’s tail will die soon, true, but so will the lizard itself. In ten years or so. Living things die, all of them… And the tail will survive much longer than some short-living organisms. So, a dropped tail is an individual organism.
A delicacy for thought 3: Lizard is an organism because it is a unit of breeding, and every its cell works for passing the same genes on. So its dropped tail is still its. But then every bee in a hive is one organism. They all work to pass the queen’s genes on. And how about a sterilized dog? It doesn’t work for passing anyone’s genes. Ghost organism☻
A delicacy for thought 4: Ontogeny of a mammal: it is created from an ovum (part of its mother) and a sperm (part of its father). Then it is integrated with mother’s body – share vascular system with her, eat her food etc. Then it is born. In other words, a mammal is two pieces of two organisms, then those pieces merged, then part of mother’s organism, and then – an organism. Isn’t it weird?
A delicacy for thought 5: Plenty of lifeforms where you simply cannot identify an organism border. Mushrooms, for example, form complex networks of hyphae that can cover the territory of thousands football grounds. Thousands of caps across entire forest could belong to the same network. It’s just a living heap, not an organism.
Hope that wasn’t too much for a dinner
Summary: life is just a continuum, a mass of biological matter, and any attempt to systematize or segregate it will fail. Count life in biospheres – you won’t be mistaken☺ There’s always only one of those…