Life is not easily bounded

 Derek J Skillings

" ...Most of the time the living world appears to us as manageable chunks. Even a toddler can see that. We know if we have one dog or two; at a pinch, we can probably count how many trees are growing in our backyard. Natural history museums started, in part, as embodiments of early scientific approaches to ordering and cataloguing the diversity of life. This is possible only because humans can usually intuitively pick out one organism from the next – that is, because most of the creatures we come across have pretty clear boundaries in space and time...

...How come, then, the meaning of individuality is one of the oldest and most vexing problems in biology? For millennia, naturalists and philosophers have struggled to define the most fundamental units of living systems and to delimit the precise boundaries of the organisms that inhabit our planet. This difficulty is partly a product of the search for a singular theory that can be used to carve up all of the living world at its joints. But my view is that no such unified theory exists; there’s no single answer to the question: ‘What parts of the world are a part of you as a biological individual, and what parts are not?’ Different accounts of individuality pick out different boundaries, like an overlapping Venn diagram drawn on top of a network of biotic interactions. This isn’t because of uncertainty or a lack of information; rather, the living world just exists in such a way that we need more than one account of individuality to understand it...

...When you stop to think about it, the problem of individuality is (ironically enough) actually composed of two problems: identity and individuation. The problem of identity asks: ‘What does it mean for a thing to remain the same thing if it changes over time?’ or ‘What makes two entities the same kind of thing?’ The problem of individuation asks: ‘How do we tell things apart?’ or ‘What are the boundaries of an object?’ Identity is fundamentally about the nature of sameness and continuity; individuation is about differences and breaks...

...These two issues are different sides of the same coin. You can often reframe one in terms of the other to suit your focus. To pick something out in the world you need to know both what makes it one thing, and also what makes it different than other things – identity and individuation, sameness and difference. Each of these aspects of individuality also tends to come in degrees. A bee is better individuated than a swarm; and a swarm is better individuated than an ecosystem. Similarly, you are closer to the person you were yesterday than you are to the one in your baby photos... "

https://aeon.co/essays/what-constitutes-an-individual-organism-in-biology