That matters because theory suggests that the maximum sustainable yield that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels.
这一点很重要，因为理论表明，当目标鱼种的生物量为其原始水平的50%左右时，渔场才能达到可收获的最大可持续产量。
Given the extraordinary diversity of life on the planet, there must be mechanisms for speciation: the formation of two species from one original species.
考虑到地球上的生命的非凡多样性，一定存在着形成物种的机制：从一个原始物种演变为两个物种。
And you end up with a mixture of some number of the original species, and some number of new species.
最后得到混合物，原物质，和新物质的。
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