The Paleoproterozoic is the first of the three sub-divisions (eras) of the Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...

 occurring between . This is when the continents first stabilized. This is also when cyanobacteria evolved, a type of bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 which uses the biochemical process of photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 to produce energy and oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...


Before the significant increase in atmospheric oxygen almost all life that existed was anaerobic, that is, the metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 of life depended on a form of cellular respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...

 that did not require oxygen. Free oxygen in large amounts is poisonous to most anaerobic bacteria
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...

, and at this time most life on Earth vanished. The only life that remained was either resistant to the oxidizing and poisonous effects of oxygen, or spent its life-cycle in an oxygen-free environment. This main event is called the oxygen catastrophe
Oxygen Catastrophe
The Great Oxygenation Event , also called the Oxygen Catastrophe or Oxygen Crisis or Great Oxidation, was the biologically induced appearance of free oxygen in Earth's atmosphere. This major environmental change happened around 2.4 billion years ago.Photosynthesis was producing oxygen both before...

. Also the Francevillian Group
Francevillian Group Fossil
The Francevillian Group Fossil is an early, macroscopic organism. They were centimeter-sized highly organized, spatially discrete colonial organisms. Their fossils are found in the west-African country of Gabon in the Palaeoproterozoic Francevillian B Formation, a 2.1-Gyr-old black shale...

 and Grypania
Grypania is an early, tube-shaped fossil from the Proterozoic Eon. The organism could have been a giant bacterium or bacterial colony, but because of its size and consistent form, is more likely to have been a eukaryotic alga. The oldest probable Grypania fossils date to about 2.1 billion years...

 fossils and the first eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s appeared during this time.

Paleontological evidence on the Earth's rotational history suggests that ~1.8 billion years ago, there were about 450 days in a year, implying 20 hour days.

The crown eukaryotes
Crown eukaryotes
Crown eukaryotes are an artificial group of eukaryotic organisms found at the top of molecular phylogenetic trees including both eukaryotes and prokaryotes...

, from which all modern day eukaryotic lineages have arisen, date back to the paleoproterozoic sub-division. Also, during this time (~1 bya), the latest common ancestors between the ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...

 and flagellate
Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, some gymnosperms and other closely related plants...

 lineages probably diverged .

During this era the earliest global-scale continent-continent collisional belts developed, represented by the 2.1-2.0 Ga (Ga = billion year) Transamazonian and Eburnean Orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma Orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China. These continental collisional belts are interpreted as having resulted from 2.0-1.8 Ga global-scale collisional events that led to the assembly of a Paleo-Mesoproterozoic supercontinent named "Columbia" or "Nuna".

See also

(Impact events)
  • Suavjärvi crater
    Suavjärvi crater
    Suavjärvi is a lake and impact crater in the Republic of Karelia, Russia about 50 km north of the town of Medvezhyegorsk...

     2.4 billion years old
  • Vredefort crater
    Vredefort crater
    Vredefort crater is the largest verified impact crater on Earth. It is located in the Free State Province of South Africa and named after the town of Vredefort, which is situated near its centre. The site is also known as the Vredefort dome or Vredefort impact structure...

     2.023 ± .004 billion years old
  • Sudbury Basin
    Sudbury Basin
    The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geologic structure in Ontario, Canada. It is the second-largest known impact crater or astrobleme on Earth, as well as one of the oldest....

      1.849 billion years old

External links

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