Saturday, February 11, 2012

How intelligent is a single cell?

Let's look at an amoeba - a single-celled organism. Amoebas live in the water, they eat algae, bacterias, and whatever microscopic bits of dead plants and animals that float around. They eat by stretching out their shapeless body, surrounding the food and pulling it into themselves. The temporary limbs amoeba sticks out for grabbing food are called pseudopods (fake legs). The inside of the amoeba is filled with a substance called cytoplasm. There are two kinds of the cytoplasm. A layer along the membrane (the skin of amoeba) is called ectoplasm. The rest of the goo inside is called the endoplasm. The little pockets floating in it that catch food, digest it, and eliminate waste are called food vacuoles. There are also cocntractile vacuoles, they contract to squirt out extra water that seeps inside the body through thin porous membrane.
Amoeba can regulate its rate of reproduction in according to the available food supply. If the environment becomes inhospitable for whatever reason, an amoeba can secrete the material to make a hard cover for itself and to remain in suspended animation until the conditions improve. Somehow it knows when to dissolve the shell and to wake up.
Amoeba finds food using the process called chemotaxis ( Wikipedia on chemotaxis ): the movement or change in the shape or position of a cell in response to the presence of a chemical agent. Apparently amoeba's outer membrane has receptors to lead it to food. The actual mechanism of how the process works appears to be quite a mystery. The scientists noticed the process, named it, and have been studying it, but in their clever articles they use such non-scientific terms as "getting warmer" or "getting colder" and words of frustration, such as "arghhh." Because in order for the process to work as it does, the amoeba must be able to somehow remember the results of the sensors' inputs, but how it can do that no one knows.
Here is a video of chemotaxis in action - chasing a bacteria:


Amoeba Difflugia can find things that aren't just food, such as microscopic grains of sand or shells and build cool houses from them! On the left is a photo of different amoeba's houses.

The brownish-red Rhodophyta algae shows remarkably coordinated and intelligent repair skills. A Professor Jeremy Pickett-Heaps in Melbourne, Australia recorded on time-lapse video the repair of an Antithamnion cell. Unfortunately I couldn't find the video online. If anyone succeeds in finding it, please, send me a link!
The empty cell was cut in half and given to Antithamnion to fix.
"Close examination of Pickett-Heaps video, frame-by-frame, allows one to observe how it is not merely the cell contents that are restored: the broken and displaced cell wall itself is also repaired and reinstated. It is not merely patched, like a bicycle tire, but meticulously realigned and permanently healed."
"When the Antithamnion cells come to restore a shattered and empty cell
wall, they perform a greater task. In addition to reoccupying the empty cell,
they perform the delicately coordinated realignment of the disrupted and
misaligned cell wall that will result in a virtually invisible mend."
"The sequence reveals a list of tasks that a human repairer would find daunting. The damaged cell is recognized as such, the cell wall fragments are carefully realigned as the contents are reinstated, and the adjacent cells provide a replacement cell
body. This is all sensed and diagnosed, manipulated, coordinated and completed by single cells without external mediation. Were we to repair something so efficiently, we'd expect to be regarded as skillful and intelligent; yet this is a lowly Rhodophyte rising to the occasion and problem-solving to an inconceivable extent."
- These excerpts are from the article On Intelligence in Cells by Brian J. Ford published in the Interdisciplinary Science Review in December of 2009.

Here is a video of a Difflugia in its house:

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