This is a timeline of the evolution of all life on earth starting at 4.6 billion years ago.

Created for Dr.Moore's biology class at Concord-Carlisle Regional High School.

Discussion:

1) Several things that surprise me about the placement of certain events is that earth stood for about 1/4 of its existence without any life. It is also surprising that the first eukaryotic cells started evolving nearly half way through earth's existence. Its also interesting that most mass evolutions and extinctions happened in less than one billion years. My to-scale timeline is different from that in the book because it shows a better scale of the events. It is easier to understand since one can clearly see the relationship of one event to the others. When people look at the not to-scale timeline in the book they might get a serious misconception about the span of the different periods. When they see this timeline they think the the Precambrian era was relatively short when in reality it was the longest one by far. They also think the Cenozoic era was relatively long when in fact it is by far the shortest.

Some pieces of new understanding I have about groups of species on earth is the fact that the distance between the evolution of early prokaryotes and eukaryotes was so great. It took nearly half of earth history to reach the point where prokaryotic cells evolved into eukaryotic cells. I was also surprised by the fact that the distance between the evolution of the first animals and the "Cambrian Explosion" was so short. This gap is very interesting because judging by the fact that it took 2.2 billion years for eukaryotes to evolve one would think that animals would take longer than 150 million years to become the dominant organisms on earth. Finally I was also quite surprised by the fact that flowering plants evolved so recently. I would not have previously thought that flowering plants could have evolved so recently, but I would have thought that they were much older than 150,000,000 years.

Picture credits:

http://scienceblogs.com/startswithabang/upload/2010/01/i_am_not_afraid_to_believe_in/bigbang.jpg

http://journalofcosmology.com/images/FirstPlant11.jpg