生物学上的假设包括生态变化，这些变化是由昆虫和开花植物之间的共同进化，或海洋中以海底生物为食的捕食者的进化所带来的。
Biological hypotheses include ecological changes brought about by the evolution of cooperation between insects and flowering plants or of bottom-feeding predators in the oceans.
事实上，一些裸鳃亚目动物会从它们的食物中储存毒素，使得这种类似鼻涕虫的生物对捕食者来说是致命的。
Indeed, some nudibranchs store up toxins from their diet of poisonous sponges, making the slug-like creatures themselves deadly to predators.
大约4万6千年前，在一种使用工具、高度智能的捕食者入侵后不久，澳大利亚主要的陆地生物发生了一些巨大的变化。
Something dramatic happened to Australia's dominant land creatures—somewhere around 46,000 years ago, strikingly soon after the invasion of a tool-wielding, highly intelligent predator.
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