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... Science Frontiers ONLINE No. 47: Sep-Oct 1986 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Earth's womb Three recent items indicate that scientists are now recognizing how the earth's crust is tailor-made for biochemical reactions of great variety and complexity. First, E.G . Nisbet explains how subsurface hydrothermal systems are ideal places to make biochemical products, particularly in the light of the discovery that RNA molecules can extrude introns and then behave like enzymes. "The most likely site for the inorgan ic construction or an RNA chain, which would have occurred in the Archaean, is in a hydrothermal system. Only in such a setting would the necessary basic components (CH4 , NH3 , and phosphates) be freely available. Suitable pH (fluctuating around 8) and temperatures around 40 C are characteristic of hydrothermal systems on land. Furthermore, altered lavas in the zeolite metamorphic facies, which are rich in zeolites, clays and heavy metal sulphides, would provide catalytic surfaces, pores and molecular sieves in which RNA molecules could be assembled and contained. If the RNA could then replicate with the aid of ribozymes and without proteins, the chance of creating life becomes not impossible but merely wildly unlikely." The article concludes with a statement that self-replicating molecules synthesized in hydrothermal systems would be pre-adapted to "life" in the open ocean if they "learned" to surround themselves with bags of lipids. (Bag of lipids = a membrane.) (Nisbet, E.G .; " ...
Terms matched: 1 - Score: 15 - 15 May 2017 - URL: /sf047/sf047p11.htm
... TIME BBD1 Discontinuous Populations of Birds BBD2 Uncolonized Areas: Unfilled Niches BBD3 Land Birds Observed Far at Sea BBD4 Late Survival of Moas and Passenger Pigeons BBD5 Distribution Curiosities BBE THE FOSSIL RECORD OF BIRDS BBE1 The Fossil Record of Birds and Associated Paradigms BBE2 Evidence against the Dinosaur Origin of Birds BBE3 Protoavis: A Pre-Archaeopteryx Bird? BBE4 Unresolved Nature of Archaeopteryx BBE5 The Apparent Absence of Transitional Forms of Feathers BBE6 Fossils of Ostrich Ancestors in the Northern Hemisphere BBE7 Controversial Feathers of the London Archaeopteryx Fossil BBE8 Giant Fossil Eggs BBF BODILY FUNCTIONS BBF1 The Avian Respiratory System: Unique, Complex, Sophisticated BBF2 Avian Bodily Functions: Some Oddities BBG GENETICS BBG1 Species mtDNA More Diverse Than Morphology BBG2 Discordance in the Date of Divergence of Modern Birds BBG3 Discordances between Phylogenies Established from Morphology and DNA Analysis BBG4 Dearth of Introns in Birds BBI INTERNAL STRUCTURES AND SYSTEMS BBI1 Avian Magnetoreceptors: Hard to Find BBI2 Curious Internal Structures BBO ORGANS BBO1 Complexity and Sophistication of Some Owl Ear-Brain, Sound-Localization Systems BBO2 Regeneration of Brain Neurons BBO3 Curiosities of Avian Brains BBO4 The Pecten: A Unique Structure in the Avian Eye BBO5 Curiosities of Avian Eyes BBO6 High Complexity and Sophistication of the Avian Eye BBO7 Remarkable Tongue Adaptations BBO8 The Loss and Reduction of Reproductive Organs BBT UNUSUAL TALENTS AND FACULTIES BBT1 Infrasound and Atmospheric Pressure-Change Detection BBT2 Utility of Ultraviolet Vision in Birds BBT3 Echolocation: Parallel Evolution in Birds BBT4 Navigational Feats during Migration BBT5 Homing: Release Experiments BBT6 Curious Migration Phenomena: Navigation Errors? BBT7 Complexity and Sophistication of Avian Navigation BBT8 Inheritance of Migration Data BBT9 The Existence of Avian Migration BBT10 Sensitivity to Impending ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /cat-biol.htm
... in the RNA World. What besides a chemical soup might have existed before "life-as-we-know-it" arrived upon the scene? A science fiction writer like H.P . Lovecraft could certainly come up with an ominous entity based upon RNA alone. Be that as it may, a book is now on the market bearing the title The RNA World (R .F . Gesteland and J.F . Atkins, eds., Cold Spring Harbor Laboratory Press, 1993) Nature reviewed the book in its January 20 issue. In addition, the RNA World was discussed recently in Science. We now extract one nugget from each of these two sources. From Nature's review. Humans are more primitive than microorganisms in the sense that we still retain cumbersome introns (nonsense DNA) in our genes, while lowly microorganisms have been able to eliminate them. From Science. No one seems to have a clue about where RNA came from. C. de Duve ventured that: ". .. the emergence of RNA depended on robust chemical reactions -- it is wrong to imagine that some fantastic single accidental event supported the development of the RNA World." In connection with the generally accepted idea that the evolution of RNA must have taken hundreds of millions of years: ". .. de Duve suggested that, on the contrary, for such a complex chemical process to succeed it must have been relatively fast in order to avoid decay and loss of information." (Brenner, Sydney; "The Ancient Molecule," Nature, 367 ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf092/sf092b07.htm
