Evolution Current Affairs - 2019
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According to recently published study, boost in levels of oxygen may have caused three-fold increase in biodiversity (or biodiversification) during between 445 and 485 million years ago.
The study was conducted using geochemical proxies, high-resolution data and chemical signatures preserved in carbonate rocks formed from seawater. Using it, researchers were able to identify oxygen increase during Middle (or Darriwilian Stage- 460-465 million years ago) and Late Ordovician periods (mid-Katian stage- 450-455 million years ago).
According to study, this oxygenation is supported by two approaches that are mostly independent from each other. Other changes — such as ocean cooling, increased nutrient supply to oceans and predation pressures – also worked together to allow animal life to diversify for millions of years.
It was found that nearly 80% increase in oxygen levels where oxygen constituted about 14% of atmosphere during Darriwilian Stage and increased to as high as 24% of atmosphere by mid-Katian stage.
The explosion of diversity, recognised as Great Ordovician Biodiversification Event brought about rise of various marine life, tremendous change across species families and types, as well as changes to Earth, starting at bottom of ocean floors. It also brought on geological changes to the Earth.
This study suggests that atmospheric oxygen levels did not reach and maintain modern levels for millions of years after Cambrian explosion, which is traditionally viewed as time when ocean-atmosphere was oxygenated. Oxygenation of atmosphere and shallow-ocean took millions of years, and only when shallow seas became progressively oxygenated, major pulses of diversification able to take place.