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Darwin i l'evolució Guerrero, R. i M. Berlanga. Orígens
de la vida a la Terra. Contribució dels microorganismes a l’evolució del
planeta Origins of the life on the Earth. The contribution of microorganisms to the evolution of the planet In the history of life on this planet there were three crucial events that led to the Earth we know today: (1) The origin of life, or biopoiesis, which may have occurred 3.85 billion years ago. Based on studies of Venus and Mars, life may also have begun on those planets, but probably did not persist for long. (2) The evolution of ecosystems, or ecopoiesis. Had the recycling of matter not evolved soon after the origin of life (i.e., the use of metabolic products from some organisms as a source of nutrients for others), the Earth’s resources would have been exhausted within 300 millions years, and life would have disappeared. (3) The development of the eukaryotic cell (i.e., cells with a differentiated nucleus), also known as eukaryopoiesis (or eukaryosis). The first forms of life were prokaryotic cells (without a differentiated nucleus), and had their genetic material dispersed in the cytoplasm. During the first 2 billion years of evolution, prokaryotes were the only inhabitants on Earth, and they “invented” all of the metabolic strategies that we know today. A simple metabolic “mistake”, the production of oxygen, led to aerobic life. A strategic mistake, endosymbiosis, produced the eukaryotic cell. Evolution always advances by means of necessary yet indeterminate mechanisms. |
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