Biological Evolution Began More Than Three and a Half Billion Years Ago

Earth was formed about 4.5 billion years ago, and the first evidence of life dates to more than 3.5 billion years ago. In 1996, scientists working in Greenland found not fossil remains but chemical evidence of life from as far back as 3.85 billion years ago, forms of carbon embedded in rock that appear to have a distinctly biological origin. Somewhere on Earth during its first billion years there arose the first simple organism, capable of replicating its own structure from a template (RNA?) that was the first genetic material. Because the terrestrial atmosphee at the dawn of life was nearly devoid of oxygen, and because there were few microorganisms to scavenge organic compounds formed by natural processes, these compounds were relatively stable. Given this stability and eons of time, the improbable became inevitable: the organic compounds were incorporated into evolving cells to produce increasingly effective self-reproducing catalysts. The process of biological evolution had begun.

مواضيع ذات صلة

تثبيت النتروجين Nitrogen Fixation

دورة اليوريا urea cycle

المصير الايضي للأحماض الامينية

ايض الأحماض الامينية والبروتينات metabolism of amino acids and proteins

اكسدة الأحماض الدهنية Oxidational of fatty acids

ايض الدهون metabolism of lipids

ايض الكاربوهيدرات metabolism of carbohydrates

انتقال الالكترونات والفسفرة التاكسدية Electron transport and Oxidative phosphorylation

الفسفرة التاكسدية Oxidative phosphorylation

دورة حامض الكلايوكسيليك Glyoxylic acid cycle

عملية التركيب الضوئي photo synthesis

الاجسام الكيتونية Keton bodies