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Name: Jessica B.
Status:  student
Age: 16
Location: N/A
Country: N/A
Date: 2/21/2004


Question:
I am doing an experiment about the Theory of Spontaneous Generation. I have done three tests with bread then placing them in petri dishes. The first bread was dry, second got 40 water drops and third got 40 sucrose drops (5% sucrose solution). I wanted to know which one should mold the most after one week, i know it isnt dry but between the other two i hav no idea. How would i disagree with Spontaneous Generation (what would be my reasons) and how would i explain to non believers that life does not evolve from non-life? Thank you in advance.. I am in deep need of help!!!


Replies:
Jessica,

First, you should probably re-name your project. Spontaneous generation implies that life can arise from non-living substances. Your mold growth experiment will simply test how quickly already living mold spores can settle upon and grow in the media you've selected. The experiment you are carrying out will not test whether life can arise from that which is not or ever has been alive.

Probably the best argument against spontaneous generation is the fact that no experiment ever performed has produced any living material from dead atoms. Indeed, many experiments have demonstrated that precursors (building blocks) of life can be produced in the lab. However, no unguided, random combination of simple dead elements has ever produced any material that meets the criteria of a living organism. Much as some scientists would like to believe and prove otherwise, although it can be sustained by that which is not alive, life has not yet been produced from non-living material.

Regards,
ProfHoff 811


The "original" experiment refuting "spontaneous generation" was done using common house flys and maggots. When raw meat at room temperature was covered with a cloth tent so that the flies could not land on the meat -- no maggots hatched. The uncovered meat produced maggots because the flies were able to lay their eggs in the meat hence producing the maggots. The experiment you are doing is more difficult because your "test life" is bread mold and mold spores being so much smaller can be carried by air currents to the bread. However, there is a way to do the experiment, I think.

Make a growth medium. It could be sugar and bread, or a commercial agar growth medium that you should be able to buy through your school. Sterilize the growth medium and the petri dishes by boiling them for about 10 min. to kill of all bacteria and mold. You could also use canning jars. You need to keep both samples wet by adding boiled sterile water to each every couple of days so that "drying out" is not a factor. You will have to arrange some sort of syphon to add sterile water without opening the sterile control. Possibly a piece of rubber tubing that you sterilize with ethanol or isopropanol prior to "watering your garden" so to speak. This is the tricky part.

Then keep one dish open for say an hour each day. Keep the other one covered. In a few days the one you keep open each day should pick up some spores of some sort of "invisible" life force -- but the other one shouldn't if you are careful to maintain its isolation from drafts of air.

Nonetheless, given you are dealing with microscopic invaders, you will have to be really careful.

Vince Calder


It is tempting for me to give you the proper experimental procedure to follow but this is a great opportunity for you to do some research and then put your imagination to work with some sound reasoning. I suggest you look up the works in spontaneous generation done by Pasteur, Reti, and spallanzani. Pasteur's work might be the easiest to work from... chicken soup...

pf


There are two ways you can go here. You can operate on pure belief, and simply have faith that what you believe is true; or you can use science to try to find out what is true. You can't do both at once, because belief before proof is the opposite of science. It is one thing to make an initial guess, for the purpose of organizing a program of research in which you try honestly to discover what is true. It is an entirely different thing to begin with a belief, focus your attention on facts that seem to support your belief, and try to explain away or minimize the importance of facts that seem not to support it. If you're going to use science, the first thing you have to be is honest.

Some things can be proven, and some things cannot. I don't know whether or not spontaneous generation is actually possible, and I can live without having an answer. But I can't think of any single step in the process that has been shown to be impossible, or even seems likely to be shown so.

Tim Mooney


First of all, your experiment doesn't have anything to do with spontaneous generation. It only shows that mold needs moist conditions to grow and will grow faster with a more concentrated source of carbon (sugar). If you refer back to Pasteur and Needham and Spallanzani, they were trying to demonstrate that life could not generate within a closed system. For example, Pasteur devised a way of sterilizing (made free of living things) a broth yet leaving it open to the air. He made a "swan necked" flask that prevented bacteria and fungi from entering the flask, yet let oxygen in. It didn't show signs of life for over a year, until he broke off the neck which allowed dust and fungi to enter. What you need to do is somehow sterilize the bread in a closed container, and have a control of the same set up with bread that is not sterile or is not closed and see which grows mold. The closed container shouldn't grow anything, as long as bacteria and mold are prevented from getting to it. You need to show that the life is not coming from within the system, only from outside of it.

Van Hoeck



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