Tuesday, November 02, 2010

"Weird" Science #4: Symbiosis, Part 1

I'm writing this as if it is its own separate subject, even though, in my mind, it's not. (It's closely related to what I began to touch on in my preceding post about Soil.)

My friend Perry Marshall encouraged me to read some books by Lynn Margulis, former wife of Carl Sagan. He mentioned her books in his article The New Atheism, Genesis 2 & Symbiogenesis. What he said there intrigued me. But then I wrote to him and he made some stronger recommendations. So I picked up a number of Margulis' books and was promptly impressed.


If you have any training in modern biology, you will, I'm sure, find me hopelessly behind the times. But I might as well reveal my inadequate training--or, perhaps, my failure as a student in high school.

Until I had begun looking at Margulis' Kingdoms & Domains, I was still working largely under a two-kingdom model of biology: there are plants and there are animals. Of course I knew there were bacteria and other microbes. But I don't think I ever placed them into a hierarchy of biological kingdoms. I think I considered them as a kind of cross between or not fully within either the plant or animal kingdom.

So it came as quite a shock when I discovered there are at least five biological kingdoms now recognized in the profession: prokaryotic (non-nucleated) Bacteria, eukaryotic (nucleated--i.e., having a nucleus) Protoctista (unicellular microorganisms), and the three eukaryotic multicellular kingdoms of Plants, Animals, and Fungi.

And then, upon a little further study, I found that even Margulis' taxonomy is . . . well . . . a little parochial. I found that many biologists actually prefer to speak of six kingdoms: the prokaryotic Bacteria (now identified as Eubacteria), and the eukaryotic Protoctista (or Protists), Plantae, Animalia and Fungi--as Margulis acknowledges, plus another kingdom of prokaryotes (non-nucleated organisms), the Archae or Archaebacteria, which are distinguished from the Eubacteria primarily by genetic differences.

As Wikipedia says,
Based on such RNA studies, Carl Woese divided the prokaryotes (Kingdom Monera) into two groups, called Eubacteria and Archaebacteria, stressing that there was as much genetic difference between these two groups as between either of them and all eukaryotes. Eukaryote groups, such as plants, fungi and animals may look different, but are more similar to each other in their genetic makeup at the molecular level than they are to either the Eubacteria or Archaebacteria.
Well, it turns out there are other ways of dividing the kingdoms. The Wikipedia article actually concludes with a kind of throw-up-your-hands-in-despair gesture when it says, "[R]esearch in the 21st century does not support the classification of the eukaryotes into any of these systems."

But back to my notes about Margulis.
Margulis' prime thesis in Microcosmos, Symbiotic Planet, and Acquiring Genomes, is that random mutation is a minor contributor at best to genomic drift (and, therefore, evolutionary change-through-time). Far more significant, she urges, is the acquisition and integration of genomic information through symbiotic merger of organisms, . . . most especially at the level of bacteria.

Indeed, she suggests that the nuclear contents of all eukaryotes come from bacteria: the chloroplasts from cyanobacteria and the mitochondria from oxygen-respiring proteobacteria. The basic cell itself, she suggests, comes from a merger of motile eubacteria and protein-synthesizing archaebacteria.

Perry Marshall provides a simple, graphically-engaging presentation of the basic ideas on his Cosmic Fingerprints website.

But he does more than that. A lot more. He proposes that
over the last 3.5 billion years . . . [DNA] has efficiently adapted and evolved from a single cell to occupy every ecological niche imaginable.

From the frozen ice sheets of the Antarctic to the punishing heat of the Sahara. From the ants under your kitchen sink to glorious singing birds in the Amazon rain forest.
This did not happen through accidental random mutation, . . . [but] through an ingenious algorithm that engineers its own beneficial mutations.
In essence, he says, God engineered into DNA (and all the carriers of genetic information--i.e., viruses, bacteria, and all the eukaryotic organelles that bear genetic information) . . . --God engineered these things to work together (through symbiosis) and intermingle (symbiogenesis) and self-adapt and "upgrade" to survive and thrive in virtually all future circumstances.

I encourage you to read Perry's paper. It's quite easy to read and rather inspiring, actually! Even if you're a committed anti-evolutionist. I hope you'll engage in the thought-experiment Perry suggests.

But what I have just written about: That, too, was not really where I wanted to go with this post.

But I think it's as far as I'm going to get.

So next time I'll try to bring Weird Science #3 (Soil, Part 1) together with Weird Science #4 (Symbiosis, Part 1) to generate . . . well . . . you'll see.

Maybe I'll call it Soil Symbiosis. Or something like that.
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