"The question of when oxygen reached anything like modern levels is a topic we are still trying to pin down, but it likely wasn't until closer to half a billion years ago," Gibson said. pubescens has helped establish when eukaryotes began to photosynthesize, it's still unclear when Earth's oxygen levels rocketed to modern levels, Gibson said. "It was then able to pass the DNA that codes for photosynthesis down to its offspring, and now, essentially all modern plants use the same organelle - the chloroplast - for photosynthesis." The analysis suggests that "1.25 billion years ago, a complex but microscopic organism 'swallowed' a simple photosynthetic bacterium and gained its photosynthetic powers," Gibson told Live Science in an email. vastly varying water ages in the water cycle Exchanges of water between hydrological compartments at key interfaces inuence the water age distribution more than previously assumed Variation from complete to nearly absent mixing of water at the interfaces in the critical zone affects the water ages in compartments Correspondence to: M. pubescens, they used a molecular clock analysis - that is, a computer model that uses rates of genetic change to calculate evolutionary events - to figure out when photosynthesis likely began in eukaryotes.
pubescens lived between 1.06 billion and 1.03 billion years ago, with its most likely age being 1.047 billion years old, Gibson said.Īfter the researchers determined the age of B. pubescens in 1990 in the journal Science, stating that the algae - which sported the first widely accepted evidence for photosynthesis in plants (which includes algae) - was between 1.2 billion and 720 million years old.īut this time window was vast, so in the current study, Gibson and colleagues narrowed it by collecting and dating new samples of the black shale found in rock layers around the algae fossils. Researchers originally published dates for B. However, there was more uncertainty when it came to more complex organisms' ability to photosynthesize. "This early photosynthesis is responsible for the very earliest atmospheric oxygen," Gibson said.
"Prior to about 2.5 billion years ago, there was essentially no oxygen in the ocean," Gibson said.
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