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anonymous

The Archean Eon - 0 views

forces.si.edu/...02_02_02.html

cyanobacteria archaen

shared by anonymous on 26 Jan 16 - No Cached
  • As cyanobacteria created more free oxygen, the amount of oxygen in the atmosphere reached one percent of today’s level, which is 21 percent.
  • anonymous on 26 Jan 16
     
    Cyanobacteria and oxygen level
jiminp

Proterozoic: Changes in the Earth's Atmosphere - 1 views

paleobiology.si.edu/...proterozoic4.html

proterozoic climate

shared by jiminp on 26 Jan 16 - No Cached
  • Earth’s early atmosphere contained only small amounts of free oxygen
  • The oxygen-rich atmosphere that evolved later, and upon which oxygen-breathing life now depends, was a result of the origin of photosynthesis.
  • During the Precambrian, vast numbers of single-celled algae and cyanobacteria living in the seas eventually released enough oxygen to transform the environment.
  • jiminp on 26 Jan 16
     
    changes in the atmosphere during the Proterozoic.
jiminp

Proterozoic Era: Timeline & Facts | Study.com - 0 views

study.com/...c-era-timeline-facts-quiz.html

oxygen climate evolution proterozoic

shared by jiminp on 26 Jan 16 - No Cached
  • During the timeline of the era, several different events took place, eventually helping to shape the Earth as we know it today.
  • During the Proterozoic, the Earth had cooled considerably from the previous Hadean eon when the planet was covered by molten lava.
  • Near the end of the Proterozoic, ice sheets were growing towards the equator, and the entire planet was possibly engulfed under a thin layer of snow and ice.
  • ...1 more annotation...
  • Life during the Proterozoic began to evolve from simple single cell organisms into more advanced single cell organisms
  • jiminp on 26 Jan 16
     
    This article talks about the climates, evolution of life and increase in oxygen during the Proterozoic.
juliane_g

Images: Bizarre, Primordial Sea Creatures Dominated the Ediacaran Era - 0 views

www.livescience.com/7-ediacaran-period-images.html

ediacaran sea

shared by juliane_g on 26 Jan 16 - No Cached
  • juliane_g on 26 Jan 16
     
    Information on the sea in the Ediacaran era During the Ediacaran period, about 635 million to 541 million years ago, oxygen was sparse, the oceans were murky and marine organisms ate by absorbing nutrients floating around in the water.
emmab25

Introduction to the Ceratopsians - 1 views

www.ucmp.berkeley.edu/...ceratopsia.html

Cretaceous Ceratopsians fossils

shared by emmab25 on 26 Jan 16 - No Cached
  • five-ton animal the size of a car, with a giant bony frill on its head, and you've got a fairly accurate picture of a ceratopsian dinosaur such as Triceratops.
  • are found only in the Late Cretaceous of North America; they are among the last of the dinosaurs (other than the birds of course).
  • Ceratopsians were ornithischians, or "bird-hipped" dinosaurs.
  • ...7 more annotations...
  • The oldest ceratopsians appeared at the beginning of the Cretaceous, about 140 million years ago. In the Late Cretaceous, about 100 million years ago, the ceratopsians began to diversify in North America and in Asia.
  • Forms without the enormous horns and frills of Triceratops, in the family Protoceratopsidae, include the Mongolian genus Protoceratops and the unusual bipedal, frill-less dinosaur Psittacosaurus ("parrot-lizard").
  • Their "beak" and rows of grinding cheek teeth suggest that they fed on tough vegetation. The huge, heavy "frill" of ceratopsians such as Triceratops may have served as armor against the attacks of saurischian predators like Tyrannosaurus, which lived in the same time and place as Triceratops.
  • other ceratopsians had smaller frills and/or frills with large openings; such frills would have been little defense against a predator. So ceratopsian frills may also have functioned as heat radiators, or signaling devices, or to attract mates, in addition to whatever protective function they may or may not have had.
  • Recent work on the oxygen isotopes found inside the bony frill, which indicate the relative temperatures of different parts of the bone, supports the first of these hypotheses: the frills functioned as heat radiators.
  • Ceratopsians probably traveled in herds; there are "bone beds" in the western United States that contain the bones of hundreds of individuals of the same species of ceratopsian.
  • f attacked, the herd could stampede, or "circle the wagons" and fend off predators. In terms of animals living today, it may be best to think of ceratopsians — at least the larger ones — as analogues of elephants or rhinos: large herbivores in herds that relied on horns and attitude to protect themselves.
jiminp

Proterozoic Eon | geochronology | Britannica.com - 0 views

www.britannica.com/...Proterozoic-Eon

proterozoic eukaryote oxygen

shared by jiminp on 26 Jan 16 - No Cached
  • The Proterozoic Eon extended from 2.5 billion to 541 million years ago and is often divided into the Paleoproterozoic (2.5 billion to 1.6 billion years ago), the Mesoproterozoic (1.6 billion to 1 billion years ago), and the Neoproterozoic (1 billion to 541 million years ago) eras.
  • Megascopic eukaryotes first appeared about 2.3 billion years ago and became widespread by about 1.8 billion years ago.
  • Eukaryotes employed a form of respiration and oxidative metabolism; they had a central nucleus that could split into separate sex cells, and so for the first time a mixed and variable genetic code could be passed to younger generations.
  • ...1 more annotation...
  • Many mountain belts formed during the Proterozoic
  • jiminp on 26 Jan 16
     
    Useful for the period. 
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