Aim
When dividing the world into zoogeographical regions, Alfred Russel Wallace stipulated a set of criteria by which regions should be determined, foremost the use of generic rather than species distributions. Yet, recent updates of Wallace's scheme have not followed his reasoning, probably explaining in part the discrepancies found. Using a recently developed quantitative method, we evaluated the world's zoogeographical regions following his criteria as closely as possible.
Location
Global.
Methods
We subjected presence–absence data from range maps of birds, mammals and amphibians to an innovative clustering algorithm, affinity propagation. We used genera as our taxonomic rank, although species and familial ranks were also assessed, to evaluate how divergence from Wallace's criteria influences the results. We also accepted Wallace's argument that bats and migratory birds should be excluded (although he was contradictory about the birds) and devised a procedure to determine the optimal number of regions to eliminate subjectivity in delimiting the number of regions.
Results
Regions attained using genera (eight for mammals and birds and six for amphibians) strongly coincided with the regions proposed by Wallace. The regions for amphibians were nearly identical to Wallace's scheme, whereas we obtained two new ‘regions’ for mammals and two for birds that largely coincide with Wallace's subregions. As argued by Wallace, there are strong reasons not to consider these as being equivalent to the six main regions. Species distributions generated many small regions related to contemporary climate and vegetation patterns, whereas at the familial rank regions were very broad. The differences between our generic maps and Wallace's all involve areas which he identified as being uncertain in his regionalization.
Main conclusions
Despite more than 135 years of additional knowledge of distributions, the shuffling of generic concepts, and the development of computers and complex analytical techniques, Wallace's zoogeographical regions appear to be no less valid than they were when he proposed them. Recent studies re‐evaluating Wallace's scheme should not be considered updates as such because they have not followed Wallace's reasoning, and all computer‐based analyses, including this one, are subject to the vagaries of the particular methods used.
B or A is the answer
Explanation because i know this question before
The ocean and the present atmosphere themselves are not leftovers from the original atmosphere of Earth. However, they do contain components within them that give us and scientists ideas of what Earth's past atmosphere was like.
Some example include:
1) Ice cores - scientists may go to Antartica or Alaska and stick this metal tube into the ice to remove what is known as an "ice core". This is then taken back to the lab for analysis. So what happens is that this ice as we know is constantly melting and freezing with different seasons and climate change. So, when the ice starts to crystallize, particles like carbon dioxide, sulfur etc may get trapped as bubbles in the ice. This is what scientists look for in ice coring and this is how they know that Carbon dioxide levels were relatively high back then (Not as high compared to now).
2) Ocean sediment cores - this is the exact same process of the ice cores except they take cores of sediments (esspecially calcium carbonate that contains oxygen). As you know, CaCO3 is found in the exoskeletons of organisms that die and build up on the ocean floor.
Those are some of the main ways that the present atmosphere and oceans have leftovers from the original atmosphere of Earth.
Hope that helped!
