The following paragraphs are from an essay about ecologist Robert Paine's research. To make the essay most logical, in what order should the paragraphs be arranged?
- 1For decades, the prevailing consensus among ecologists was that ecosystems were structured from the bottom up. In this view, the diversity and abundance of plants and other primary producers determined the complexity of the animal communities above them, with each species in the food web exerting a roughly equal influence on the environment's overall balance.
- 2To challenge this dominant paradigm, ecologist Robert Paine designed a simple yet radical experiment in 1963 along the rocky coastline of Makah Bay, Washington. He selected tidal pools containing a variety of marine invertebrates and systematically pried loose every purple starfish (*Pisaster ochraceus*) he could find, throwing them into the ocean to observe how the remaining community would react in their absence.
- 3The consequences of this removal were swift and devastating. Without the starfish to prey on them, the mussel population rapidly expanded, monopolizing the rock surfaces and crowding out algae, limpets, and chitons. Within a few years, what had been a rich, biodiverse habitat of fifteen distinct species was reduced to a barren monoculture of a single dominant competitor.
- 4Based on these dramatic findings, Paine introduced the concept of the 'keystone species' to describe an organism that exerts a disproportionately large effect on its community relative to its abundance. Just as a physical keystone prevents a stone arch from collapsing, certain predators, though few in number, play an indispensable role in preserving the diversity and stability of their entire ecological network.
Cevap
The correct sequence begins with the paragraph introducing the prevailing historical consensus of bottom-up control, followed by the paragraph detailing Robert Paine's experiment to challenge that paradigm, followed by the paragraph describing the resulting mussel explosion, and concluding with the paragraph introducing the keystone species concept.
The correct logical order begins by establishing the historical consensus that ecosystems were structured 'from the bottom up.' The narrative then transitions to Robert Paine's attempt to challenge 'this dominant paradigm' by removing starfish. Next, the passage describes 'the consequences of this removal,' showing how the mussel population took over. Finally, the passage concludes by explaining how, 'based on these dramatic findings,' Paine formulated the theory of 'keystone species.'
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Paragraph-Level Transitions