The origin of life Presented by: Arzhang Davazdahemami

The origin of life

Presented by:

Arzhang Davazdahemami

Overview: Introduction Spontaneous generation Scientific hypothesis

Reduced atmosphere Meteorite compact Hot sea vent

conclusion

Introduction Earth; the only known

place for living creatures He is ~4.5 billion years old ~500 million years

subjected to bombardment of meteorites

After a few million years

the life began

Introduction

The oldest microfossil ever seen is 3.5 years old

Our investigate in rocks formation estimate the time of 3.8 million years ago

What is the source of small organic molecules?

Overview: Introduction Spontaneous generation Scientific hypothesis

Reduced atmosphere Meteorite compact Hot sea vent

conclusion

Spontaneous generation

Until early 19th there was a believe that living creatures can form from non living matter

Ignorance of spontaneous creation by Pastor experiments which comes up with evolution theory of Darwin

Beginning of theoretical hypothesis about creation…

Overview: Introduction Spontaneous generation Scientific hypothesis

Reduced atmosphere Meteorite compact Hot sea vent

conclusion

Reduced atmosphere

A hypotheses which based on an atmosphere with small amount of oxygen in 3.8 million years ago

It was a popular hypotheses in early 20th and attracted lots of scientist

The most ingredients of atmosphere was:

Methane, Water vapor, Ammonia, Hydrogen Miller and Urey started the new era of astrobiology by

the means of an experiment which was a module for cycle of rain in 3.5 million years ago

Miller-Urey experiment

Result

Table

Amount of amino acids in Murchison meteorite and products of Miller experiment are

roughly the same

Facts…

Although the modulus of Miller-Urey works properly to introduce the first step of appearance of life on earth by showing that sugars are made from formaldehydes,

there was estimate in their experiment which is really small amount of oxygen.

And in these days we believe that atmosphere was not that much reduced…

Overview: Introduction Spontaneous generation Scientific hypothesis

Reduced atmosphere Meteorite compact Hot sea vent

conclusion

Meteorite

4 billion years ago earth was under meteorites bombardment

One of those groups of meteorites are carbonaceous chondrites

Interesting because of their organic carbon, standard amino acids and nucleic acid

Facts

Supporter of this hypothesis think that there was enough organic carbon to start the process of prebiotic synthesis.

But the question is would that organic materials survive according to intensive heat of entering the atmosphere?

The result of this hypothesis is completely based on assumption about Density of the atmosphere Composition of the atmosphere Size of the meteorite Components of the meteorite Etc.

Overview: Introduction Spontaneous generation Scientific hypothesis

Reduced atmosphere Meteorite compact Deep-sea vents

conclusion

Deep-sea vents

There is a ideal place for biological activity because of independency of sun light

There is a reaction of iron(II) sulfide and hydrogen sulfide which release free energy necessary to reduction of carbon dioxide to organic molecules

In this hypothesis there is a assumption that This complex metabolism would organize itself And the products of that metabolism never escape from surface

Deep-sea vents

Stetter and colleagues showed that hydrogen sulfide with iron(II) would work as reducing agent Acetylene to ethane Mercaptoacetic acid to acetic acid But no reduction of CO2

Afterward new studies show that there is a possibility to reduce carbon monoxide when FeS spiked with NiS

Carbon monoxide might have been present in the gases escaped from vents

If metal sulfides can be shown to catalyze the synthesis of organic molecules, the vent hypothesis would become popular as a origin of biomers…

Conclusion

There are lots of hypothesis that introduce origin of life.

some of them are popular, lots of them not.

None of them are proven but also not expelled.

The work nowadays is to use more than one source to show how does the life begin…

References

Orgel, L. E. (1998) Trends in biochem. Sci. 12, 491-495 Orgel, L. E. (1998) Origin of life evol. 1, 91-96 Orgel, L. E. (1994) Sci. Am. 4, 76-83 Kumar, A. (2008) Astrophys. Space Sci. 317, 267-278