History of Life on Earth Crossword
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
 
 
Down: 1) the age of the Earth 2) recognized correlation3) appeared 1.5 to 1.2 billion years ago4) occurred with the development of oxygen-releasing photosynthesis6) divides time into eons, eras, and smaller units7) time of visible life8) the longest time division on the geological time scale9) responsible for the recognition of fossils Across: 5) evidence of past life including bones and shells10) evolution appeared of these during the phanerozoic era11) two classes of fossils12) organic matter in the fossil has turned to stone13) determines the age of the fossil14) the shortest time period on the geological time scale15) different layers of rock
 

 

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