# Cell size? **URL:** \ **Category:** Factual Questions\ **Created:** [August 14, 2022, 4:32pm UTC](https://boards.straightdope.com/t/cell-size/969645 "2022-08-14T16:32:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2022, 4:32pm UTC](https://boards.straightdope.com/t/cell-size/969645/1 "2022-08-14T16:32:16Z")
Lets suppose we are starting with one celled animals and then go one step up into multi celled animals. Are cell sizes relatively similar in size? Do some microscopic animals consist of larger cells? Is it safe to assume that larger animals always contain more cells? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [August 14, 2022, 4:42pm UTC](https://boards.straightdope.com/t/cell-size/969645/2 "2022-08-14T16:42:11Z")
Most are in the same general ballpark, but they do vary. According to The Google, the world’s largest single-celled organism is an aquatic alga called Caulerpa taxifolia. It can grow to a length of six to twelve inches ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2022, 5:01pm UTC](https://boards.straightdope.com/t/cell-size/969645/3 "2022-08-14T17:01:06Z")
WOW! I was thinking microscopic! It does clearly demonstrate that cells can vary greatly in size. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [August 14, 2022, 5:03pm UTC](https://boards.straightdope.com/t/cell-size/969645/4 "2022-08-14T17:03:55Z")
The _Caulerpa taxifolia_ apparently grows up to 10 feet. It is far larger than millions of multicelled organisms, including some animals, plants, and fungi. [This page](https://sciencenotes.org/what-is-the-largest-unicellular-organism/) gives giants for algae, protozoa, and bacteria. The fewest-celled organism is the fungi named _Tetrabaena socialis_ with only four microscopic cells. However, [sea urchin embryos contain only two cells](https://learn.genetics.utah.edu/content/cloning/clonezone/), if that counts. And _[Bicellum brasieri](https://www.livescience.com/billion-year-old-fossil-animal-evolution.html)_ fossils have been found, that straddle the border between unicelled and multicelled organisms. To be pedantic, Animalia is a separate kingdom, so none of the others should be called animals, though I know that’s the common term. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2022, 5:15pm UTC](https://boards.straightdope.com/t/cell-size/969645/5 "2022-08-14T17:15:37Z")
The thing I am wondering about is, could higher carbon levels have an effect on soil bacteria that amounted to kind of a changing of the guard where less dominant bacteria could be becoming more dominant in response to higher co2 levels. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [August 14, 2022, 5:37pm UTC](https://boards.straightdope.com/t/cell-size/969645/6 "2022-08-14T17:37:47Z")
Even multi-cellular organisms can have largish cells. The human ovum is about 1mm, large enought to see with the naked eye. A human neuron has a tiny body (100 microns), but its axon can be a meter long. (it’s super thin, so not naked-eye visible, but quite long.) ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 14, 2022, 6:05pm UTC](https://boards.straightdope.com/t/cell-size/969645/7 "2022-08-14T18:05:15Z")
I am not a biologist and in one of my casual readings I found that even most Single cellular organisms are not really a single organism. It was pointed out that that mitochondria in a cell’s nucleus did not share the cell’s DNA, and most (some cells do not have mitochondria) cells are in a symbiotic relationship with mitochondria. I found that interesting because when I learned about cells, it was never pointed out that Mitochondria have a whole world of their own, and they just rent their space in the nuclei. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2022, 6:09pm UTC](https://boards.straightdope.com/t/cell-size/969645/8 "2022-08-14T18:09:35Z")
> [@am77494](#): > > I found that interesting because when I learned about cells, it was never pointed out that Mitochondria have a whole world of their own, and they just rent their space in the nuclei. I would like to know more about the relationship they have. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [August 14, 2022, 6:11pm UTC](https://boards.straightdope.com/t/cell-size/969645/9 "2022-08-14T18:11:19Z")
I’m not sure what you mean by this, but current CO2 levels were far, far higher 50 MYA and so there should be ample evidence if CO2 levels affected the types of bacteria. Of course, they have been high for much too short a time now to make any noticeable global difference. > **[A Graphical History of Atmospheric CO2 Levels Over Time | Earth.Org](https://earth.org/data_visualization/a-brief-history-of-co2/)** > > As the most abundant greenhouse gas in our atmosphere, CO2 levels have varied widely over the course of the Earth’s 4.54 billion year history. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2022, 6:19pm UTC](https://boards.straightdope.com/t/cell-size/969645/10 "2022-08-14T18:19:50Z")
> [@Exapno\_Mapcase](#): > > I’m not sure what you mean by this, but current CO2 levels were far, far higher 50 MYA and so there should be ample evidence if CO2 levels affected the types of bacteria. Of course, they have been high for much too short a time now to make any noticeable global difference. Yes I know they are higher, and I am wondering if identifiable changes in soil biology are taking place because of this. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 14, 2022, 6:32pm UTC](https://boards.straightdope.com/t/cell-size/969645/11 "2022-08-14T18:32:49Z")
> [@am77494](#): > > even most Single cellular organisms are not really a single organism. It was pointed out that that mitochondria in a cell’s nucleus did not share the cell’s DNA, and most (some cells do not have mitochondria) cells are in a symbiotic relationship with mitochondria. Mitochondria and chloroplasts _originated_ as independent symbiotic cells. But it is no longer accurate to say that any cell consists of multiple separate organisms. Mitochondria do still have a separate genome, a truncated legacy of their origin, but it now has few genes. Most genes that were originally present in the symbiotic cell are now part of the nuclear genome, or have been lost. Mitochondria are no longer separate viable organisms. They originated in the distant evolutionary past as independent symbiotic organisms, but they have now most definitely “merged” to become part of a single organism. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [August 14, 2022, 6:54pm UTC](https://boards.straightdope.com/t/cell-size/969645/12 "2022-08-14T18:54:10Z")
You often read that there are more bacteria in your gut than cells in your body ([cite](https://www.science.org.au/curious/people-medicine/gut-bacteria)): If > Estimates are that there are between 30 trillion and 400 trillion microorganisms in the human gut, and from three to 100 times more bacteria in the gut than there are cells in the human body. is true (and the ranges indicated are wide enough for that statement to be true) it follows that the cells of gut bacteria are much smaller than the average human cell. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 14, 2022, 6:56pm UTC](https://boards.straightdope.com/t/cell-size/969645/13 "2022-08-14T18:56:22Z")
> [@Pardel-Lux](#): > > the cells of gut bacteria are much smaller than the average human cell. Yes, prokaryotic cells are generally much smaller than eukaryotic cells. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 14, 2022, 7:49pm UTC](https://boards.straightdope.com/t/cell-size/969645/14 "2022-08-14T19:49:47Z")
There is sufficient variability in the size of cells that some multicellular animals are the prey of single-celled predators. [Stentor](https://en.wikipedia.org/wiki/Stentor_(ciliate)), a unicellular ciliate, eats [Tardigrades](https://en.wikipedia.org/wiki/Tardigrade) and [Rotifers](https://en.wikipedia.org/wiki/Rotifer) - both of which are multicellular animals with distinct organs and such, but are smaller than the single-celled Stentor (which can ingest them whole). Large specimens of Stentor are naked eye visible. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 14, 2022, 7:58pm UTC](https://boards.straightdope.com/t/cell-size/969645/15 "2022-08-14T19:58:04Z")
> [@Riemann](#): > > but they have now most definitely “merged” to become part of a single organism. Why are they “merged” when they maintain their own separate DNA ? ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [August 14, 2022, 8:02pm UTC](https://boards.straightdope.com/t/cell-size/969645/16 "2022-08-14T20:02:16Z")
Because mitochondria don’t maintain sufficient cellular machinery to exist on their own. They are completely dependent on the larger cells to supply them with various things and protect them from the hazards outside the cell. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 14, 2022, 8:10pm UTC](https://boards.straightdope.com/t/cell-size/969645/17 "2022-08-14T20:10:12Z")
> [@am77494](#): > > Why are they “merged” when they maintain their own separate DNA ? The mitochondrial genome contains only 37 genes out of thousands that were present in the original symbiont. That’s nowhere near enough to be viable as a separate organism. The evolution of the mitochondrial genome is interesting. We know why there is strong selective pressure for mitochondrial genes to move to the nuclear genome (or to be lost if the nuclear genome already has them). It’s principally because there is immense oxidative stress in the mitochondrion. This can damage DNA, so it’s better for genes to be located somewhere safer and for the gene product to be transported in as required. What we don’t understand in any detail is the countervailing reason why these 37 genes have been retained. > **[Mitochondrial DNA | Origin](https://en.wikipedia.org/wiki/Mitochondrial_DNA#Origin)** > > Nuclear and mitochondrial DNA are thought to have separate evolutionary origins, with the mtDNA derived from the circular genomes of bacteria engulfed by the ancestors of modern eukaryotic cells. This theory is called the endosymbiotic theory. In the cells of extant organisms, the vast majority of the proteins in the mitochondria (numbering approximately 1500 different types in mammals) are coded by nuclear DNA, but the genes for some, if not most, of them are thought to be of bacterial origin, h... ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 14, 2022, 8:26pm UTC](https://boards.straightdope.com/t/cell-size/969645/18 "2022-08-14T20:26:26Z")
> [@HoneyBadgerDC](#): > > Lets suppose we are starting with one celled animals and then go one step up into multi celled animals. Just to comment on this. You speak of going “one step up” as though it’s an unremarkable thing for a single-celled organism to become bigger by adding more cells. It’s not. The evolution of multicellarity is a highly significant qualitative change. Single-celled organisms all have their own independent evolutionary future. Multicellularity requires cellular differentiation, all programmed by one genome; and that all somatic cells sacrifice their own evolutionary future, dedicating themselves to the future of a small number of germline cells. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 14, 2022, 8:52pm UTC](https://boards.straightdope.com/t/cell-size/969645/19 "2022-08-14T20:52:50Z")
> [@gnoitall](#): > > A human neuron has a tiny body (100 microns), but its axon can be a meter long. And if we want to talk neurons, humans may feel a bit adequate standing next to an Aplysia. > **[Aplysia](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4024469/#S3title)** ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 14, 2022, 10:08pm UTC](https://boards.straightdope.com/t/cell-size/969645/20 "2022-08-14T22:08:50Z")
> [@Riemann](#): > > But it is no longer accurate to say that any cell consists of multiple separate organisms. Agreed. But is it accurate to say that the mitochondria is the same organism as the cell ? From what I understood, a woman who only has sons will essentially not pass on the mitochondria to the next generation. Also that sperms do not carry mitochondria. So a mitochondrial “DNA line” can go extinct while the main cell keeps going on. Is this correct ? [Next page](https://boards.straightdope.com/t/cell-size/969645.md?page=2)