Explain and expand. • Science is cumulative.
• Science is cumulative. . The basic understanding of plate motions was considered as conceptual revolution.. Although the concepts of plate tectonics were proved primarily by the study of the ocean basins, they have revolutionarized our understanding of continental geology.
About 225 million years ago, at the end of the Permian period, fully half the families of marine organisms died out during the short span of a few million years — a prodigious amount of time by most standards, but merely minutes to a geologist. This late Permian extinction was the greatest of several mass dyings that have punctuated the evolution of life during the past 600 million years. No problem in paleontology has attracted more attention or led to more frustration than the search for the causes of these extinctions. Since the Permian extinction dwarfs all the others, it has long been the major focus of inquiry. If we could explain this greatest of all mass dyings, we might hold the key to understanding mass extinctions in general. During the past decade, important advances in both geology and evolutionary biology have combined to show which one of the many J proposals is correct and even how it happened. This solution has 1 developed so gradually that some paleontologists scarcely realize that their oldest and deepest dilemma has been resolved. If we reconstruct the history of continental movements, we realize that a unique event occurred in the latest Permian: all the continents coalesced to j form the single supercontinent of Pangaea. Quite simply, the consequenc- 1 es of this coalescence caused the great Permian extinction. But which consequences and why? Such a fusion of fragments would produce a wide array of results, ranging from changes in weather and oceanic circulation to the interaction of previously isolated ecosystems. Here we must look to advances in evolutionary biology — to theoretical ecology and our new understanding of the diversity of living forms. Many studies now indicate that diversity — the numbers of different species present in a given area — is strongly influenced, if not 148 largely controlled, by the amount of habitable area itself: the larger the area, the greater the number of species. We must first understand two things about the Permian extinction and the fossil record in general. First, the Permian extinction primarily affected marine organisms. It did not strongly disturb the few terrestrial plants and vertebrates then living, and diversity of land organisms may have increased at the time. Second, the fossil record is very strongly biased toward the preservation of marine life in shallow water. We have almost no fossils of organisms inhabitating the ocean depths. Thus, if we want to test the theory that reduced area played a major role in the Permian extinction, we must look to the area occupied by shallow seas. We can identify, in a qualitative way, two reasons why a coalescence of continents would drastically reduce the area of shallow seas. The first is basic geometry. If each separate land mass of pre-Permian times were completely surrounded by shallow seas, then their union would eliminate all area at the sutures. The second reason concerns the mechanics of plate tectonics. That paleontology's outstanding dilemma should be solved with the help of advances in two other disciplines is not surprising. When a problem has proved intricable for more than 100 years, it is not likely to yield to more data collected in the old way and under the old rubric. Theoretical ecology and plate tectonics have provided paleontologists with the right questions to solve their hardest riddle. Ш Give the Russian for: a short span of; a prodigious amount of time; by most standards; to lead to frustration; the key to understanding; to coalesce to form the single continent; a wide array of results; to bias toward
вымирание; привлекать внимание; поиск чего-либо; в общем; важные продвижения; предположение; решение проблемы;! постепенно; едва ли; осознавать; разрешение дилеммы; последствия соединения (сращение); разнообразие видов; в данном районе Ш Focus on structures. • If we could explain..., we might hold the key to understanding... • If we reconstruct the history..., we'll realize that... • The larger the area, the greater the number of species. • The diversity of organisms might have increased. • That dilemma should be solved is not surprising.
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