科普知识学英语 古海洋中的有毒海水延缓了复杂生命的形成

科普知识学英语 古海洋中的有毒海水延缓了复杂生命的形成 海量资料下载 免费学习英语 www.englishvip.com/xinlw.htm (申请网址) A new model suggests that inhospitable hydrodgen-sulphide rich waters could have delayed the spread of complex life forms in ancient oceans. The research, published online this week in the journal Nature Communications, considers the composition of the oceans 550-700 million years ago and shows that oxygen-poor toxic conditions, which may have delayed the establishment of complex life, were controlled by the biological availability of nitrogen. In contrast to modern oceans, data from ancient rocks indicates that the deep oceans of the early Earth contained little oxygen, and flipped between an iron-rich state and a toxic hydrogen-sulphide-rich state. The latter toxic sulphidic state is caused by bacteria that survive in low oxygen and low nitrate conditions. The study shows how bacteria using nitrate in their metabolism would have displaced the less energetically efficient bacteria that produce sulphide -- meaning that the presence of nitrate in the oceans prevented build-up of the toxic sulphidic state. The model, developed by researchers at the University of Exeter in collaboration with Plymouth Marine Laboratory, University of Leeds, UCL (University College London) and the University of Southern Denmark, reveals the sensitivity of the early oceans to the global nitrogen cycle. It shows how the availability of nitrate, and feedbacks within the global nitrogen cycle, would have controlled the shifting of the oceans between the two oxygen-free states -- potentially restricting the spread of early complex life. Dr Richard Boyle from the University of Exeter said: "Data from the modern ocean suggests that even in an oxygen-poor ocean, this apparent global-scale interchange between sulphidic and non-sulphidic conditions is difficult to achieve. We've shown here how feedbacks arising from the fact that life uses nitrate as both a nutrient, and in respiration, controlled the interchange between two ocean states. For as long as sulphidic conditions remained frequent, Earth's oceans were inhospitable towards complex life." Today, an abundance of nitrate, in the context of an oxygenated ocean, prevents a reversion to the inhospitable environment that inhibited early life. Determining how Earth's oceans have established long-term stability helps us to understand how modern oceans interact with life and also sheds light on the sensitivity of oceans to changes in composition. 一种新的模型表明可能有延迟传播的复杂的生命形式在远古海洋，荒凉hydrodgen的硫化物丰富的水 域。的研究，本周在线发表在Nature杂志上传播，认为组成的海洋550-700万年前，表明贫氧毒性条 件下，这可能推迟建立复杂的生命，被控制的生物有效性的氮。在现代海洋相比，古老的岩石中的数据 表明，早期地球海洋深处的含有少量的氧，富含铁的状态和一种有毒的硫化氢丰富的状态之间翻转。后 者有毒的硫化物状态是由细菌生存在低氧和低硝酸盐条件。研究表明细菌如何使用其代谢硝酸较少能量 高效的细菌产生的硫化物流离失所 - 意思是防止在海洋中的硝酸盐积聚有毒的硫化物状态。 由英国埃克塞特大学的研究人员在UCL(伦敦大学学院)和南丹麦大学，利兹大学，普利茅斯海洋实验 室，合作开发的模式，揭示了全球氮循环的敏感性，早期海洋。它显示了如何硝酸盐的可用性，并在全 洛基国际英语 竭诚为您服务 海量资料下载 免费学习英语 www.englishvip.com/xinlw.htm (申请网址) 球氮循环的反馈，本来两个氧自由州之间的海洋转移 - 可能限制复杂的生命早期的传播控制。 埃克塞特大学的理查德?博伊尔博士说:“从现代海洋数据表明，即使在贫氧的海洋，这明显的全球规模的硫化物和非硫化物条件之间的交流是很难实现的，我们已经证明这里怎么反馈所产生的事实，生活中使用硝酸既是一种营养，呼吸，控制两洋州之间的交流。只要硫化物的情况仍然频繁，地球上的海洋荒凉的对复杂的生命。“ 今天，大量的硝酸盐，含氧海洋的上下文中，可以防止复归荒凉的环境，抑制早期的生活。确定地球上的海洋是如何建立长期稳定，有助于我们了解现代海洋与生活，也揭示了海洋来改变组合的敏感度。 “成千上万人疯狂下载。。。。。。 更多价值连城的绝密英语学习资料， 洛基内部秘密英语，技巧，策略 请在 网上 申请报名” 洛基国际英语 竭诚为您服务