Early Evolution: From The Appearance Of The First Cell To The First Modern Organisms Prime Tappe Dell'evoluzione Cellulare. English

It is now accepted that the first cells derived from simpler "objects", and that their descendants became more and more complicated and ordered until their evolutionary transformation into modern cells, namely, cells endowed with the same basic structures and mechanisms as those existing today. Although the appearance of the first modern cells goes back at least two billion years, many scholars believe that it occurred almost four billion years ago. In that case, the Earth's formation, which took place quite quickly about 4. 6 billion years ago, is in close proximity to the originoflife. There is disagreement not only about the moment ofappearance ofmodern cells, but also as to their early evolution. Ideas on the first steps in cellular evolution vary considerably, and our present knowledge is so limited as to be little more than vacuous. Why discuss it then? Precisely because it is an empty space that needs to be filled! Does it make sense only to discuss things which are well-known and well­ documented? Is this the best way to interpret that spirit of exploration of the unknown which is at the very heartofscientific endeavor? The idea that it is idle to venture into fields which are poorly documented has been long supported, even in cases similar to those dealt with here, for example, the evolutionary phases which took place before the first cell. This book aims to fill a gap in the evolution of living things. Actually, over the last few decades there has been increasing interest in the astronomical and physicochemical problems involved in the events which determined the appearance of the first cell; for almost two centuries the evolution of present-day and past species has given rise to a great many investigations and much discussion; moreover, in the last few years important contributions have come from the discoveries about their DNA. By contrast, there has been very little investment in attempts to understand the evolutionary processes which linked the first cell to the first modern organisms, of which are included even the most ancient fossils. In this field, even simple working hypotheses are often lacking. This book discusses at length these missing links and the origin of the basic structures of modern cells ranging from the propelling organelles of bacteria and nucleated cells to the organelles that the nucleated cells acquired by .. Front Matter....Pages I-VI Introduction....Pages 1-3 The First Cell....Pages 4-23 Modern Cells: Prokaryotic and Eukaryotic Descents....Pages 24-52 Prokaryotes: The Flagellum....Pages 53-62 Prokaryotes: The Outer Membrane....Pages 63-74 Prokaryotes: Trends towards Complexity....Pages 75-84 The Appearance of the Nucleus....Pages 85-103 Eukaryotes: Dictyosomes....Pages 104-108 Eukaryotes: The Mitochondrial Symbiosis....Pages 109-121 Eukaryotes: Plastidial Symbioses....Pages 122-135 Eukaryotes: The Cilium....Pages 136-154 Eukaryotes: Complexity and Gigantism....Pages 155-164 Conclusions....Pages 165-167 Back Matter....Pages 168-175 Martino Rizzotti. Includes Bibliographical References (p.[169]-173) And Index.