Clearly, this single celled, is performing computation. 'Knowledge' of self, environment and the relationship between the two worlds has to be encoded in an active and dynamic fashion. While networks and networks of cells are an incredible and fascinating system, clearly inspirational and massively insightful for the development of intelligence outside of biological systems, one could and should consider the argument that by jumping to networks as systems for computational intelligence, we skipped a step in describing how cells (and thereby networks of cells) encode computation and intelligence. I think that a major step in theories of intelligence and mind could be possible by reconsidering intelligence at a cellular and single cell level.
https://en.wikipedia.org/wiki/Dinoflagellate https://en.wikipedia.org/wiki/Kleptoplasty https://aem.asm.org/content/78/3/813
Check out his latest publications here: http://brianjford.com/wbbjf10.htm
I think the most interesting components to me are histology and transtrictomics as they relate to cellular behavior. The fact that cells have to rely on membranes and voltage potentials, but through compartmentalization are able to create a dynamic computational environment, is the really mind-blowing bit.
Its always funny to me when people want to reduce the behavior of non-human lifeforms to something akin to a program written on a tape drive (see below), when we know that DNA exists in a dynamical 3-dimensional form when in the somatic phase.
In the case of the Dinoflaggelates, such a action could be performed by an incredibly simple state machine, making the definitions of the above terms incredibly weak.
ETA: I'll add that you put a lot of calculating and work on the Dinoflaggelate that is likely performed by evolution. The "calculations" would just be done by the genetic equivalent of a look up table.
Based on my reading of your comment it seems like you would consider cellular behavior to be a kind of linear program, which really only shows a fundamental lack of understanding of the nature of the system and biology.
However, if the part I care about is only the implementation of the state machine, I can transfer that to any other substrate or just pure logic.
If I'm looking at the "cognition" necessary to swap out the current algae for a new one, I don't need to care about what makes the state machine in the cell function, whether it's the relative concentration of two different proteins, the pH of the cell, or whatever. If the intelligence part of it can be reduced to a simple state machine, the other stuff doesn't factor into it.
The biology matters for biologists, and because perhaps it can give us insight into more abstract lessons in computation. I don't think one level of biology is more informative than the other per se.
Further, as I understand, for each and every level here, you could find an alternate school of thought that would offer a slightly or a considerably different model.
Essentially, you reach the point where so many different human ideas have to compete in understand phenomena X in the brain that integrating them goes the mental capacity of a given human being - taking into account that every model here is going to be a very leaky abstraction.
So we basically need a computer program or interface, not even to really simulate the brain but to integrate existing models on whatever level of abstraction we're working on.
One would want something that lets one shift seemlessly between models. Essentially, a system that lets you take the information that is now contained in scientific papers and make it as interactive as a spreadsheet. Anyway, we're quite far from such a situation.
https://neuronaldynamics.epfl.ch/online/Ch4.S4.html
A fantastic resource on a lot of this material (basically a peer reviewed wikipedia): http://www.scholarpedia.org/article/Bifurcation
It shows how little we know of how biological neural networks actually work (imo 95% of "work" would be how learning occurs, that's the really interesting bit). I know this is hard to study, but wow, there's a huuuge gap here.