I thought I recall some one telling me that there was a species of ameoba in the amazon or some such that was the size of a quarter. (fricken huge for an ameoba). Is this true? Is it even possible?
Well, all I can tell you is that I remember seeing a picture (In National Geographic) of a group of about 4 or 5 bacteria that barely squeezed onto the head of a pin. In other words, almost visible to the naked eye. 'Don’t know if there are any bigger critters than that, or even if the creatures pictured were “true” single-celled organisms.
Ranchoth
[Xenophyophores - the giants of the protozoan world
- 10cm to 25cm single-celled ‘monsters’ live in the depths of our oceans!](http://www.microscopy-uk.org.uk/mag/artnov98/xeno1.html
)
In layman’s terms, could you suggest what this means for us humans as a species?
Should I cash in my 401K and party like there’s no tomorrow?
The link doesn’t work
i’ll fix it!!!
http://www.microscopy-uk.org.uk/mag/artnov98/xeno1.html
Did i earn a cookie? An Ameba cookie?
Pictures, anybody? 
As far as I learned in SAT II Bio (9th grade), single-celled organisms could not grow past a certain size, a size far less than any coin. This is because, so I learned, of diffusion. A single cell does not have a circulatory system composed of tissue, lest it lose its single-cell-hood. Therefore nutrients must diffuse through the cell naturally.
Now, suppose we start with a normal-sized amoeba, then increase its volume. We soon find that its surface area (the workable area through which it must absorb all its nutrients) does not increase as fast as its volume does. Therefore, there swiftly comes a point where the nutrients simply do not diffuse fast enough to keep the cell alive. We did a nifty demonstration of this in the aforementioned Bio class using agar cubes of various sizes and a diffusing dye.
http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/IMAGES/G-550.gif
http://www.soc.soton.ac.uk/CHD/Sediments/seds_afen/xeno_2.jpg?99,123
http://www.ecology.com/expeditions/deep-east-producers-logs/9-27-28-01/
The second picture looks like it’s grinning an evil grin…
majinbourg, many protozoans have interior pathways – the details I’m hazy on; this board needs a good cytologist! – that improve the flow of nutrients, dissolved oxygen, wastes, etc. So the objection you raise applies only to the abstract “it’s nothing but a nucleus and undifferentiated cytoplasm” single-celled critter that is a simplification rather than an actuality. (Much like why “bumblebees can’t fly according to physics” is wrong.)