Early Life C1.2

Cameron Falls Contains an outcrop of Alberta’s oldest sedimentary rock. Rock formed from many layers of pre-existing rock or organic matter. You can see layer upon layer of sediment compressed into solid rock. The properties of the sediments, and the fossils preserved in each strata, provide information about they type of environment that existed when they were deposited 1.5 billion years ago. Fossil – the evidence or remains of early life preserved in Earth’s crust Strata – the layered bands within sedimentary rock

An Ancient Coast Sedimentary rock formations in the Rocky mountains indicate that several large rivers deposited sand, clay and silt into an ocean A sandwich of sedimentary rock 11 km thick is currently evident.

Life Gets Started Some scientists think that single celled organisms where the earliest form of live (3.8 million years ago.) Archaea bacteria, which can live in water at 150 C are though to be the relatives of this bacteria. Next came the cyanobacteria which deposited calcium carbonate (limestone). They created stromatolites (layered structures) which we call trace fossils (remains left by an organism.)

Hot Oceans Early Earth was filled with the frequent volcanic eruptions and poisonous gases The oceans were very hot, over 100o C. One organism that tolerate the heat and poisonous gas was Archaea. They were first found in the boiling waters of a hot spring in Yellowstone National Park. Deep-sea thermal vents release intense volcanic heat and hydrogen sulfide gas. Archaea thrives in these conditions and feed on the hydrogen sulfide which is poisonous to humans. This group of extremist life forms may be the closest living evidence of Earth’s earliest life.

Source of Oxygen PHOTOSYNTHESIS: Cyanobacteria contained calcium carbonate which traps the suns energy to make glucose (food) and oxygen. This process is called photosynthesis. PHOTOSYNTHESIS: Carbon Dioxide + Water  Glucose + Oxygen

Other Evidence of Oxygen Red & gray banded iron can be found in sedimentary rock. Gray bands have iron only. The red bands are iron (III) oxide which must of reacted with oxygen. (see reaction below.) 4Fe3+(aq) + 3O2(g)  2Fe2O3(s)

Snowball Earth Late in the Precambrian Era, life barely survived during the most significant ice age ever. Ice covered most of the planet for nearly ten million years. This is often called Snowball Earth. Some scientists believe that the stresses placed upon organisms as the result of changes in their habitat during this deep freeze, and the thaw that followed, may have resulted in an explosion in species diversity that led to the first complex creatures.

Assignment Add the events highlighted in the section to your time line. Practice questions 1.2 Questions Pg. 305 #1-8