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Long before Dinosaurs, virtually all life on Earth ... (continued)
Barite is a mineral consisting of barium sulfate that records the
history of oxygen in the atmosphere.
Looking at Earth’s productivity through ancient history provides a
glimpse into how life is likely to behave over its entire existence –
in addition to informing observations of atmospheres on planets
outside our solar system.
According to a statement released by Stanford university,
those samples revealed that Earth indeed did experience huge
changes to its biosphere – the part of the planet occupied by living
organisms – ending with an enormous drop in life approximately
2.05 billion years ago, that may also be linked to declining oxygen
levels.
As for cyanobacteria, they came back from the brink of winking
out.
Usually unicellular, they often string together in colonies large
enough to see with the naked eye. They are celebrated for being
the “architects of the Earth’s atmosphere”, and are the oldest
known fossils, more than 3.5 billion years old.
As a tribute page at the University of California, Berkeley
observes: “The other great contribution of the cyanobacteria is
the origin of plants. Each chloroplast with which plants are able
to make food for themselves is actually a cyanobacterium living
within the plant’s cells.”
Cyanobacteria were the world’s first oxygen-producing
photosynthetic organisms. The fossil record is spotty for
cyanobacteria.
“This shows that even when biology on Earth is comprised
entirely of microbes, you can still have what could be considered
an enormous dying-off event that is not otherwise recorded in
the fossil record,” said Malcolm Hodgskiss, co-lead author of a
new study published in Proceedings of the National Academy
of Sciences. “The fact that this geochemical signature was
preserved was very surprising. What was especially unusual
about these particular barites is that they clearly had a complex
history.”
Distinct types of cyanobacteria; courtesy
Idaho State University
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SCIENCE EDUCATIONAL NEWS VOL 68 NO 4