From ScienceDaily:
The ability to generate oxygen through photosynthesis — that helpful service performed by plants and algae, making life possible for humans and animals on Earth — evolved just once, roughly 2.3 billion years ago, in certain types of cyanobacteria. This planet-changing biological invention has never been duplicated, as far as anyone can tell. Instead, according to endosymbiotic theory, all the “green” oxygen-producing organisms (plants and algae) simply subsumed cyanobacteria as organelles in their cells at some point during their evolution.
Endosymbiotic theory (life forms acquire useful units the way corporations acquire businesses) is a favourite in the coffee room around here but it is not up there with gravity. Still, do say on:
Fischer and his colleagues found that a single branch of cyanobacteria — dubbed Oxyphobacteria — were likely the first and only group to evolve oxygenic photosynthesis. Their closest relatives, Melainabacteria, live in the guts of animals (including humans) among other environments, and do not produce oxygen. And while one might suggest that Melainabacteria simply lost the ability to produce oxygen over time, the next most closely related cyanobacteria after those, described in the paper as Sericytochromatia, also do not engage in oxygenic photosynthesis.
“This nails down that Oxyphobacteria were really the only ones to ever invent this globe-shaping chemical process,” Fischer says.
We don’t really know that. And devolution (organism just somehow loses trait, survives anyway) is common.
The 41 new species fall into both Melainabacteria and Sericytochromatia, the latter of which had not been described before this paper. All names of these organisms are subject to change, as taxonomists catch up with the team’s discoveries. “We know they’re there, and we know their gene repertoire. Now we can start putting them into evolutionary trees, and begin efforts to isolate them and study their physiology and ecology,” says James Hemp, an Agouron Postdoctoral Scholar at Caltech when the research was conducted, and coauthor of the Science article. Paper. (paywall) – Rochelle M. Soo, James Hemp, Donovan H. Parks, Woodward W. Fischer, Philip Hugenholtz. On the origins of oxygenic photosynthesis and aerobic respiration in Cyanobacteria. Science, 2017; 355 (6332): 1436 DOI: 10.1126/science.aal3794 More.
This is great research as long as the researchers don’t demand, as evidence for achievement, that their study subject finds a place on the tree of life. Maybe back then it just didn’t quite work that way.
See also: Early Earth oxygen debate: Will the shooting stars please rise
Researchers: Small amount of oxygen 3.8 billion years ago
Did a low oxygen level delay complex life on Earth? (October 31, 2014)
Early Earth was indeed “extremely oxygen-poor compared to today” (January 16, 2015)
Small pre-Cambrian oxygen jump kickstarted complex life
(July 24, 2015)
Oxygen Does Not Equal Life – Implications for Abiogenesis? (September 15, 2015)
Researchers: Cyanobacteria responsible for Earth’s early oxygen
(November 28, 2015)
Animals didn’t “arise” from oxygenation, they created it, researchers say
Theory on how animals evolved challenged: Some need almost no oxygen
and
New study: Oxygenic photosynthesis goes back three billion years
If you want to get involved with the oxygen and evolution controversy, make some tea and check the following links as well: Researchers: Low oxygen levels delayed evolution two billion years
Earlier than thought: Oxygen deficit Oxygen on Earth and delayed evolution?
See also: Early Earth oxygen debate: Will the shooting stars please rise
Researchers: Small amount of oxygen 3.8 billion years ago
Did a low oxygen level delay complex life on Earth? (October 31, 2014)
Early Earth was indeed “extremely oxygen-poor compared to today” (January 16, 2015)
Small pre-Cambrian oxygen jump kickstarted complex life
(July 24, 2015)
Oxygen Does Not Equal Life – Implications for Abiogenesis? (September 15, 2015)
Researchers: Cyanobacteria responsible for Earth’s early oxygen
(November 28, 2015)
Animals didn’t “arise” from oxygenation, they created it, researchers say
Theory on how animals evolved challenged: Some need almost no oxygen
and
New study: Oxygenic photosynthesis goes back three billion years
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