Biology K 101

Biology K 101

  • Submitted By: chloe7
  • Date Submitted: 06/24/2013 1:30 AM
  • Category: Science
  • Words: 652
  • Page: 3
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The World Goes Oxic
* Up until this time the Earth was “anoxic”... completely without any uncombined molecular oxygen (O2).
* There were plently of oxygen atoms of course, but they were all chemically combined in water (H2O) and CO2 and various other compounds.
* But now the cyanobacteria began “modern style” photosythesis in millions of stromatolites, for millions of years...
* We find huge deposits of evidence for what happened next... the world went rusty!
* In many parts of the world (including Western Australia) we find huge deposits of “Banded Ironstone”; rock containing layers of iron oxide (Fe2O3).
* The iron mineral is very fine grained as if precipitated from a water solution. The explanation is that, in the anoxic early conditions a lot of iron was dissolved in the oceans in the soluble form of Fe2+ ions.
* As the cyanobacteria began releasing vast quantities of O2 oxygen, it reacted with the iron forming the insoluble Fe2O3 iron oxide (which is RUST).
Eventually, after about 200 milion years, all the iron was precipitated, and now the oxygen began building up in the atmosphere... the air became “OXIC”.

Draw a flow chart to represent this information.

The First Eucaryotic Cells
* All the “more advanced” living things on Earth today are characterized by cells containing many organelles Prior to about 1.5 billion years ago, all life on Earth was “procaryotic” meaning that the cells lack a true nucleus,mitochondria, chloroplasts, etc. The living procaryotes of today are the bacteria and cyanobacteria. Without true organelles to organize their cell functions better, the procaryotes have to remain very tiny, single cells in which diffusion distances are small, and the SA/Vol ratio is high.
* And that’s how life on Earth might have remained forever, except some cells ate some smaller cells, but failed to digest them. The small cells lived on inside their “host” in a relationship that soon became mutualism, and...

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