Notes

-we believe the earth will be 4.5 billion years old
-precambrian is the largest time segment there is
-One of the reasons fossils can be lost so easily because is the greastest organism on Earth a the time was a cyanonbacteria,with a blue green algae
-The blue green algae is important for this time period is because it contains chlorophyll in it.
-Chlororphyll is what we know they use to do photosynthesis,which is the process of taking sunlight and making energy
-So we believe by the cyanobacteria giving up so much oxgen,it chaged the atmosphere to create oxgen as more of the abundant elements in it.
- We also believe by giving off this oxgen,that's how our ozone layer formed
-The ozone layer protects us from ultraviolet rays which is how we believe that new organisms were able to develop after this.
-Most of this time period is classified as marine organisms which mean they lived in the ocean
-Most of the marine organisms we see fossils record of had both gills and lungs which means that they could survive part of the time on land and part of the time in water
-At the very end of pennsylvania period,we notice that there are fossils eggs with harder coverings, meaning that animals could now move onto land and survive outside of the water
-The Palezoic era, this was a great of mountain building
- The continents were shifting and colliding together, as they did that they would fold up and build mountains
Theres also a lot of evidence of volvanic activity at this time to
-At the end of the Palezoic era,90 percent of the marine animals 70 pervent of the land animals died
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