by dennyabraham
0 subcomment
- Aside from the anthropocentric view that cells are relatively small because we are made of many of them, the increases in size of lifeforms past that of individual cells is a matter of exceeding thermodynamic and informational limits. I highly recommend the book _The Vital Question_ as an intro to the systemic view of this kind of biological complexification
- I've recently gotten into microscopy as a hobby and comparing the relative size of microbes is really interesting. There are entire animals (tardigrades for one) which can be smaller than some single celled organisms.
There are even single celled organisms which will prey upon and eat multicellular animals.
- This reminds me also of this paper: https://www.pnas.org/doi/pdf/10.1073/pnas.1115585109
"The allocation of all metabolic resources to maintenance purposes limits the size of the smallest prokaryotes and largest unicellular eukaryotes, whereas an inability to meet the ever-increasing biosynthesis rates limits the largest prokaryotes and smallest unicellular eukaryotes. Metabolic constraints for larger eukaryotes are relieved by alternative reproductive strategies and multicellularity."
- Nice article! There is another interesting perspective:
Anything selfreplicating kinda needs to be as small as possible (compared to the smallest internal mechanisms required), otherwise the replication time grows out of control:
Consider a 3D printer that can fully selfreplicate by depositing individual molecules: If this was the size of a regular printer, the replication time would be hopelessly long (>billion years even if it could deposit billions of atoms/s).
This applies somewhat universally, and is one of the reason why our current industrial tech is so unsuitable for selfreplication: Any "printing" like process (books, metal stamping, lithography) requires internal features that are much smaller than the output it produces.
by purplehat_
0 subcomment
- On Being the Right Size turned 100 this year. It's not entirely the same topic as this essay, but this reminded me of it and it's a pretty famous short essay that's worth reading if you haven't seen it.
https://teaching.hkaiser.org/fall2025/csc7103/course/papers/... (PDF 50 KB, 5 pages essay + 3 pages commentary)
- FWIW I wrote a paper on nutrient-limited growth rates of cells and how that depends on their shape. one of the interesting findings was that elongated cells can grow exponentially quickly (as observed) while spheres quickly max out.
https://arxiv.org/abs/1312.0674
- All life started from procaryotic cells. The step from macromolecules to the first cell cannot be big, otherwise it could not happen spontaneously. On the other side, it must be big enough so that the cell have enough flexibility and functionality to support complex life.
That is, the cell is small enough in order to be produced directly by molecules but large enough in order to be a full living organism (reproduction, metabolism etc). This sweet spot seems to be the cell size we observe.
Later in evolution the size disparity grew because a procaryotic cell swallowed another one to become an eucaryotic and the eucaryotic ones specialized even further.
- Reminds me of: "Gravity plays a role in keeping cells small" [0]
[0] https://www.princeton.edu/news/2013/10/24/gravity-plays-role...
- Not all are?
Largest eukaryote:
https://en.wikipedia.org/wiki/Valonia_ventricosa
largest prokaryote:
https://en.wikipedia.org/wiki/Thiomargarita_namibiensis
by kayo_20211030
2 subcomments
- > A simplistic answer is that evolution has made each cell the size best suited to its function.
Yeah. That's probably it. Really, it probably is the right answer.
by CommenterPerson
0 subcomment
- Great concepts, very well written, Kudos to the writer! I bookmarked your main site.
Also : as usual, lots of HN type nitpicking in the comments, most missing the main story.
- I feel like keeping the amount of molecules the same within the simulation needs to be justified.
How would it look like if the average amount of molecule was the same across a um?
by socalgal2
3 subcomments
- Cells are small? compared to what? An ostrich egg is a single cell
- Nitpick maybe, but I don't think oocytes are the largest cells, it pretty much has to be some sort of neuron. A sensory neuron for eg. someplace in the foot will be almost as long as the person is tall, and even if the neuron is extremely thin, it's gotta beat the oocyte for volume.
- Man that was great great great! Recommending for coworkers, I suscribed!
Thanks for the good work
- Surface area to volume ratio?
- I like explanations like this because they make biology feel much less arbitrary
- maybe god is small too?
by WorkerBee28474
0 subcomment
- Another answer is: They're not - at least in some plants:
https://en.wikipedia.org/wiki/Valonia_ventricosa
https://en.wikipedia.org/wiki/Acetabularia
- Perhaps cells are small in the first place is for efficiency. It's more efficient to perform a set of tasks with trillions of these cells in unison than one big blob.
by warrantisall
0 subcomment
- [flagged]
by BurningFrog
1 subcomments
- Cells are small compared to humans because we're made up by around 3×10¹³ cells.
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