Mel's work on Endosymbiotic Theory

3:04:57 AM CDT
Feeling Quiet
Hearing In the summertime - Mungo Jerry

Mel's work on Endosymbiotic Theory


Before the turn of the century everyone feared the Y2K disaster. Life and the world as we once understood it was suppose to cease it's existence and the population would be reduced to the ammenities of the pioneering days (bet the Amish were laughing their hats off over this thought).


I happened to be one of those poor souls everyone spent endless days laughing hysterically over because of my obsession with this very concept. My thinking was, was that if all heck was going to break loose, I wasn't going to be caught with my panties down (it's a proven fact, Mel's got a wide hide, could possibly be a crime to bear it in public, and I wasn't about to take my chances). I was feeling like Noah and the Arc. I collected canned foods and bottled water, I stocked up on medical supplies. I felt I was completely prepared to meet this evolutionary challenge head on, panties fully intact. Come New Year's Eve in 1999 and it occured to me I'd forgotten one vital element; a hand held can opener.


Now most stores consider New Year's Eve to be a holiday. Other than a gas station with some convienient ammenities, you aren't going to have any luck getting anything but microwaveable burrioto and a stale cup of coffee when the clock is ticking. I had to figure out what I could do. It had suddenly occured to me as I was looking out my back door that one of my neighbor friends had opted to stay home with her kids instead of partying like it's 1999. I quickly called her and came up with a proposition:


"If it all hits the fan, since you didn't stash any supplies away (because you were laughing too hard at me), can I use your hand held can opener in exchange for a few cans of food?"


Well, needless to say, after she was done hysterically laughing on the floor for what seemed like to me hours, she decided it wouldn't be such a bad arrangement after all. Thus, a relationship was formed between my hyeana friend and I. This is the way we chose to survive. In fact, if you really think about it, this is the way most living things choose to survive, and that being the case, why would you not expect bacteria and cells to do the same thing?


The Endosymbiotic Theory was originally conceived by Lynn Margulis, the first wife of Carl Sagan (bet their offsprings were geniuses!) in a theoretical paper she entitled The Origin of Mitosing Eukaryotic Cells in 1966. Although the idea of symbosis amoung organelles was not unique, the fact that she theorized her formulation and backed it by actually research and observation, was.


The theory maintains that ancestors of eukaryotic cells were "sybiotic consortiums" of prokaryote cells with at least one and possible more species (endosymbionts) involved. In other words, perhaps oxygen breathing bacteria invaded an anareobic amoebalike bacteria, and each performed mutually benefiting functions. The bacteria would breathe for the anareobic amoebalike bacteria, and the amoebalike bacteria would navigate though new oxygen-rich waters in search of food. This way, each of the organisms would be benefiting from their symbiotic relationship as the waters and atmosphere changed.


A simpler explanation of this theory would be:


Endosymbiosis is the concept that mitochondria and chloroplasts are the result of years of evolution initiated by the endocytosis of bacteria and the blue-green algae which, instead of becoming digested, became symbiotic.


And Mel's explantion:


You got something I need so I won't kill you today; let's get married and have lots of kids!


In order to walk with any of these explanations, one would have to establish if mitochondria and chloroplasts are actually living things. So exactly what defines life?


Biologists use the word 'life' for both the processes of living, and for the things that carry out those processes. Life, too, connotes the relationships amoung living things, past and present: it includes the entire living world - the biosphere - and the whole history of "life on earth".


You could say, yeah, but the cell itself is still alive, so wouldn't that make the mitochondria and chlroplasts living also? You betcha. But the question here is, is mitochondria and chloroplasts living entities alone? What would define an entity?


Deoxyribonucleic acid (DNA).

DNA is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms.


Both mitochondria and chloroplasts contain DNA that is fairly different from that of the cell nucleus and that is similar to that of bacteria.


Now the idea becomes more plausible, but there are alternate theories on the evolution of eukaryotic cells:


1) The mitochondria and chloroplasts are developments of the *"in-folding" of the cell membrane. Such that the rest of the cell, being relieved from power house duties, became highly developed and evolved.

*(I believe the word in-folding was substituted for "invaginations", which means, to enclose, sheathe, or to fold so that an outer becomes an inner surface).

2) The bacterium somehow developed externally, and the casing around the bacterium is now what we call the eukaryotic cell.


Right about now, I'm feeling like a contestant on "Let's Make a Deal!" Which theory should I subscribe to?


Well, if you were to believe that these organelles were a creation of the cell itself (the in-folding theory), you'd have to concede that that the eukaryotic cell is one smart organism. I'm thinking, if it's so darn smart, why doesn't it come out and get a job and make a living for itself like the rest of us joes?


The external development theory to me, is a kinder, gentler way of habitation. It's the 70's child singing, "All we are saying...is give peace a chance". It's kind of like living in a camper in your parents driveway. Sooner or later, someone's going to say, "Isn't there an easier way to do this?" For me, I'd love to see this as the way the evolution of the eukaryotic cell evolved, but after viewing about 2 hours of the discovery channel's "Shark week", you can understand why I don't believe nature behaves this civilized.


Nature has a way of discriminating the weak from the strong. Those that cannot adapt and change to meet the demands of it's surroundings are eliminated in the game usually by one of it's hungry constituents.


So perhaps, the bacteria looked over to the blue-green algae and said, "you look mighty tasty", and because the blue-green algae couldn't get the heck outta dodge, it was bacteria dinner, but the algae being smarter than the average bacteria dinner, decided not to "go to the light" and instead decided to contribute some form of support to it's new surroundings. (Want proof on this one? How about you try interviewing the average college student?)


Based on what I understand about the world around me, the endosymbiotic theory is the best one for me to subscribe to.


http://en.wikipedia.org/wiki/Lynn_Margulis

http://www.mrs.umn.edu/~goochv/CellBio/lectures/endo.html

http://www.gpc.edu/~pgore/students/w96/joshbond/symb.htm

http://en.wikipedia.org/wiki/Serial_endosymbiosis_theory

http://en.citizendium.org/wiki/Life

http://en.wikipedia.org/wiki/Chloroplasts

http://en.wikipedia.org/wiki/Mitochondria

http://en.wikipedia.org/wiki/Protein_folding