To start, what is Sanders' hypothesis? That the climatic stability of the deep sea and the rain forest accounts for the high level of species diversity found in these ecosystems.
However, the passage tells us that several observations have cast doubt on the validity of Sanders' hypothesis. These observations suggest that the climate in the Amazon has actually experienced significant fluctuations in the past.
Haffer noticed that different species of birds inhabit different corners of the basin despite the fact that the forest extends throughout the whole region. This raised a question: why would the species inhabit different parts of the forest if the whole forest had a stable climate?
Haffer noticed that there were different species found in the high and low regions of the Amazon. He proposed that, during the ice ages, the high and low regions of the Amazon experienced vastly different climates, thereby separating populations.
We are looking for the answer choice which highlights a problem with Sanders' hypothesis.
Answer choice (A) is incorrect because lines 19 and 20 explicitly state that the basin is characterized by an "absence of winter and glaciation." Therefore, Sanders could not underestimate these effects because they did not exist.
Answer choice (B) is incorrect because lines 37 and 38 tell us that the Amazon lowlands are drier than the Amazon uplands. Therefore, at least one of the physical conditions differs between these two regions.
Answer choice (C) is incorrect because we do not learn any information about the rate of extinction during the ice ages in the Amazon basin.
Answer choice (D) is incorrect because we are not provided with any information to contradict the evidence provided at the end of paragraph 1 which tells us that trees have persisted for some 30 million years nor are we provided any additional information on the length of time species have survived in the basin.
Answer choice (E) is correct because, while Sanders recognized the high level of species diversity, he failed to account for the distribution of species throughout the basin i.e. the fact that different species of birds inhabit different corners of the basin.
Hope this helps! Please let us know if you have any further questions.
