Coevolution of Earth Systems Webquest
NAME:______
COEVOLUTION OF EARTH SYSTEMS WEBQUEST
Three of the four Earth systems (spheres) were developing and forming simultaneously early in Earth’s history after the Earth formed 4.6 billion years ago. For about the first 800 million years the atmosphere, lithosphere, and hydrosphere were forming and continually changing. Then about 3.8 billion years ago the earliest life forms appeared. These life forms were photosynthetic cyanobacteria. The appearance of these life forms set forth in motion a series of changes in the Earth systems. The Earth systems continue to change today but at a much faster rate largely due to human activity.
Search the websites below (and other web searches) to answer the following questions:
1) Explain how the appearance of cyanobacteria impacted each of the other Earth’s spheres (atmosphere, lithosphere, and hydrosphere).
2) How did the changes in those 3 spheres cause changes in the evolution of life forms on Earth?
http://www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/
Iron bands
http://disc.sci.gsfc.nasa.gov/ozone/additional/science-focus/about-ozone/ozone_formation.shtml
Formation of the Ozone Layer
One billion years ago, early aquatic organisms called blue-green algae began using energy from the Sun to split molecules of H2O and CO2 and recombine them into organic compounds and molecular oxygen (O2).This solar energyconversion process is known as photosynthesis.Some of the photosynthetically created oxygen combined with organic carbon to recreate CO2 molecules.The remaining oxygen accumulated in the atmosphere, touching off a massive ecological disaster with respect to early existing anaerobic organisms.As oxygen in the atmosphere increased, CO2 decreased.
High in the atmosphere, some oxygen (O2) molecules absorbed energy from the Sun's ultraviolet (UV) rays and split to form single oxygen atoms.These atoms combined (27k jpeg) with remaining oxygen (O2) to form ozone (O3) molecules, which are very effective at absorbing UV rays.The thin layer of ozone that surrounds Earth acts as a shield, protecting the planet from irradiation by UV light.
The amount of ozone required to shield Earth from biologically lethal UV radiation, wavelengths from 200 to 300 nanometers (nm), is believed to have been in existence 600 million years ago.At this time, the oxygen level was approximately 10% of its present atmospheric concentration.Prior to this period, life was restricted to the ocean.The presence of ozone enabled organisms to develop and live on the land.Ozone played a significant role in the evolution of life on Earth, and allows life as we presently know it to exist.
http://www.astrobio.net/topic/origins/origin-and-evolution-of-life/oxygen-not-the-cause-of-the-cambrian-explosion/
How oxygen contents rose and fell 2 billion years ago Donald E. Canfield, professor of ecology and director of the Nordic Center for Earth Evolution (NordCEE) in the Institute of Biology, University of Southern Denmark. Credit: University of Southern Denmark Carbon-containing microorganisms began to sink to the bottom of the oceans, where they created carbon-rich rocks. This allowed the carbon to be stored in the seabed instead of being released into the air, and thus less oxygen was needed to react with carbon. The result was that the concentrations of oxygen could be increased. The increased oxygen levels could now attack the rocks on land and in the process release nutrients such as phosphor and iron that ended up in the oceans as nutrients for microorganisms. This led to the formation of even more microorganisms that ended their lives on the ocean floor – and so the process could start again. After a while sediment stored carbon became released to the air again, and then there was a sudden need for a lot of oxygen to react with the released carbon. Such ups and downs in oxygen contents have always taken place on Earth.
http://www.geography12.com/pdf/Sphere%20Interactions.pdf