The old belief that climatic stability accounts for the high level of species diversity in the Amazon River basin of South America emerged, strangely enough, from observations of the deep sea. Sanders discovered high diversity among the mud-dwelling animals of the deep ocean. He argued that such diversity could be attributed to the absence of significant (i)_____in climate and physical conditions, without which the (ii)_____of species should be rare. In the course of time new species would continue to evolve, and so the rate of speciation would be greater than the rate of (iii)_____, resulting in the accumulation of great diversity.