Chapter 14 Lesson 2 Early Earth History

PreCambrian Time Longest part of Earth’s history Includes the Hadean, Archean, and Proterozoic Eons Lasted from 4.5 billion years ago to 544 million years ago Not much is known because the organisms did not have “hard parts” and could not withstand the heat and pressure

Early History Characterized by stromatolites- layered mats of cyanobacteria Cyanobacteria- blue green algae Made their own food through photosynthesis Important because they made oxygen for our current atmosphere Ozone also started to appear to shield us from harmful UV rays

End of Precambrian era First invertebrates appear They had soft bodies so their remains were not preserved as fossils. First jelly fish, worms, and soft corals form

Paleozoic Era Organisms with hard shells are common 544 million years ago (mya) to 248 mya Warm, shallow seas covered large areas Trilobites common Vertebrates appear in this Era First vertebrates were fish like with jaws Forests appear in Devonian period so land vertebrates appear

Life on Land Many of the fish had lungs and gills. Many bottom dwellers may have had fins evolve into legs. However, all amphibians must lay eggs in water or moist area. Reptiles now evolve in the Pennsylvania period so these organisms no longer need a watery location to lay eggs.

Palezoic Era cont Mountain building occurs Appalachian Mountains form The ocean separating North America from Europe and Africa closed Several volcanic island chains that formed in ocean collided with North American plate 2nd mountain building- African plate collides with North American plate

Paleozoic Era 90 % of marine and 70 % of land species die off by the end of the era Maybe caused by climate changes or lowering of sea levels. Pangaea formed at this time and glaciers covered the southern part of Pangaea. Other theories include extreme volcanic activity. Giant comet or asteroid?