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Lab exercise to teach abiogenesis principles

Posted by SGTex on Sat, Jun 23 2012 at 06:52 PM CDT:

An Abiogenesis Demonstration for Children and Youth

As noted on the CNN education feature "Perry's Principles," recent studies indicate that only 28% of high school teachers are quite affirmative about evolution theory while 13% "explicitly advocate creationism or intelligent design by spending at least one hour of class time presenting it in a positive light." [Berman, Michael and Plutzer, Eric. "Defeating Creationism in the Courtroom, But Not in the Classroom." Science 28 January 2011: 404-405]

A remaining 60% are "cautious" and avoid lending their support to either view. It is these brave souls who are really working for the creationists, since they allow fervor to trump knowledge and effect a de facto "balanced treatment" in their classrooms.

Even if defeat in court sufficed to restrain creationist disinformation from the high schools, that would still leave kindergarten through eighth grade vulnerable to the version that is aimed at them. The very young are all but written off by science education advocates, themselves a bit "cautious" when it comes to that demographic.

A further attitudinal barrier currently mutes the voice of science in elementary and middle schools: Big Bang and abiogenesis theory, which get a lukewarm salute at best from defenders of evolution, may be seen as too involved (or too radical) for children. Yet it is they who are bound to ask about the very, very beginning.

Contrary to the yielding terms of such apologists, there does exist a scientific accounting for the earliest origins of life. The proposition that life began as chemistry has, in the last 20 years or so, emerged from the mists of conjectural fancy and developed the robustness of actual theory, substantiated ever more credibly by findings in the natural environment and by experimental studies.

This intrepid compartment of biochemistry dares attempt the fundamental inquiry, "What is life? Where does it come from?"

Editorializing done, then, I am here to offer the progressive home-schooler or the maverick small-town teacher nothing less than a recipe for comprehending and, yes, believing the abiogenesis hypothesis---courtesy of that not-inimitable pioneer in the field, Sidney W. Fox (1912-1998). It was he who discovered how readily thermal polymerization of amino acids can yield populations of impressively cell-like microsystems, and in no uncertain terms exonerated the hypothesis Aleksandr Oparin had offered back in 1924.

I adopted Fox's historic demonstration for a successful high school science project many, many years ago and will assert that his work---like that of the great Stanley Miller--- retains its elegant relevancy to this day, to the chagrin of some.

In advance of this exciting lab exercise, be sure your students know a bit about protein and amino acids. Sixth grade and higher may appreciate a description the peptide bond that is obtained in thermal polymerization:

Give an overview of cellular anatomy including the membrane and organelles such as mitochondria. Introductory microscopy should include viewing yeast and protozoa.

The procedure involves hydrolysis of protein using 6N hydrochloric acid and heating the hydrolysate in an oven, which for safety's sake should not be conducted by students but by the instructor.

-Glassware to include approximately 80 cm length of 10-mm or 12-mm Pyrex tubing, closed at one end; small Petri dishes.
-Protein---pure gelatin or gluten isolated from wheat flour by washing away the starch.
-6N hydrochloric acid, sterile water, sodium bicarbonate.
-Oven (laboratory or household). Hot plate or stovetop with a cooking oil bath, ring stand and clamp (or may improvise a stable apparatus). A cooking thermometer.
-Microscope and kit materials such as slides, forceps, probe, spatula, dropper. Cotton ball.
A little glass work may be necessary, i.e., closure of the tubing at one end using a Bunsen burner or propane torch, in effect fashioning a very tall test tube. This otherwise might be done for one by the glass vendor.

Place a small amount of protein in the bottom of the tall tube and add 3-4 mL of the hydrochloric acid solution. Stop the tube loosely with cotton to keep dust/contaminants out and submerge the bottom of the tube in the oil bath, securing this using a clamp and stand (or may fashion a lid for the oil bath with a hole for the tube, or improvise some other way for the tube to remain upright). Heat the oil just enough to start the liquid boiling and leave this (out of the reach of small children, of course) for 48-72 hours. The tall tube is in effect an air-cooled reflux, so be sure the temperature in the room is not inordinately high.

Hydrolysis has certainly occurred after, say, a weekend of boiling. Remove the tube and let it cool, then decant the yellowish solution into a Petri dish. Ventilation of the laboratory or kitchen is critical from this point, since HCl fumes are moderately hazardous; be sure they do not accumulate to be much inhaled---ideally, by use of a fan or ventilation hood. Warm the Petri dish in the oven at very low heat (not yet over the boiling point of water!) until dried, then add about 5 mL of sterile water and re-dissolve the residue and heat again until dry. Repeat this a second and third time to remove as much acid as possible, then dissolve the residue once more using 5 mL very dilute sodium bicarbonate solution (about 0.1 g of baking soda, a tiny amount at the tip of your spatula). This will likely effervesce minutely, indicating neutralization of persistent acidity, and you will have thus effected the mild salinity necessary for best results hereafter.
The next step is to perform thermal polymerization of the amino acid mixture. Place the Petri dish of dried residue in the oven, heat to a temperature of 180-190 degrees Celsius and leave to bake for 1-3 hours. The residue should darken to a reddish brown and give off a faint aroma like that of beef broth.
Ready the microscope and slides. Allow the Petri dish to cool some, but while it is still fairly warm, add room-temperature sterile water dropwise.
Promptly mount light smears of the wetted product on microscope slides, prevent drying with occasional droplets of sterile water at the edge of the cover slip and watch at 100X or 200X.
With any luck at all, behold the emergence of very remarkable analogs of the aboriginal protocell---Fox's famous "proteinoid microspheres" are known to exhibit uniformity of size and an appearance very like that of yeast cells, including a tendency to bud. In response to pressure on the cover slip or spontaneously, they may aggregate in chains or (as I recall in the case of my science project) pair up like diplococci. They may show internal compartmentalization and granules. "Feeding" with amino acid solution may cause them to grow.
In general, they are unmistakably cell-like and go to show that the vesicles proposed by abiogenesis theory surely washed up by the thousand trillion on ancient shores.

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