Question

Do some independent internet research on the Miller-Urey Experiment. Based on what you found,

• What did the experiment definitively prove?
• What did the experiment suggest?
• What criticisms of the experiment did you find? Are they convincing?

Answer 1

• Miller Urey experiment proved that several organic molecules could be spontaneously produced under reducing conditions like the early earth.
• Miller and Urey experiment suggest, molecules in reducing environment would tend to donate electrons to the atmosphere, leading to reactions that form complex molecules from simple ones. Present atmosphere is oxidizing, in which oxygen is present, removes electrons from chemical bonds, leading to less favorable conditions for spontaneous creation of organic compounds from inorganic precursors than those conditions present on early Earth. These reducing conditions and high energy levels from UV radiation, strong lightning and volcanic discharges on primitive earth, are believed to have set the state for the origin of life. The Miller-Urey experiment confirmed the hypothesis that “spontaneous generation of the first living organisms might reasonably have taken place if large quantities of organic compounds had been present in the oceans of the primitive earth.”

• Criticism-

1. The concentrations of methane and ammonia were carefully selected to ensure the production of organic molecules.

2. Experiment took the atmosphere as reducing

3. Infact they took a methane-ammonia reducing atmosphere.

4. The simulation of lightning by mild spark discharges,taken in the experiment is unrealistic.

5. The molecules produced in the Miller-Urey apparatus would be harmful to life forms that were trying to evolve.

6.They designed the apparatus to separate amino acids from the mix as soon as they were formed was not fair.

7. The amino acids produced were half left-handed and half right-handed likely to any random experient.

8. Additional molecules were formed other than amino acids,which are destructive to life.

• These are convincing because-

The Earth’s atmosphere was not confirmed to have similar concentrationa of methane and ammonia. Rather, an inert mix of carbon dioxide and nitrogen made different molecules.

There is no evidence that the Earth’s early atmosphere was reducing. Infact, considerable evidence suggests the Earth had an oxidizing atmosphere during most, if not all, of its history.

A methane-ammonia-reducing atmosphere would be fatal to life-forms.

Actual lightning would have destroyed any organics that may have been present.

Chemically the end product molecules would destroy all life forms.

If they hadn’t seperated as soon as an amino acid was formed, the next electrical spark would have rearranged the atoms into some other form.

Amino acid in organisms are always left handed.

Molecules like formaldehyde and cyanide produced are destructive for life.