Science Crossword
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
 
 
Down: 1) division of earths history into time units based largely on the types of life forms that lived only during certain periods2) longest part of earths history lasting from 4 billion years to about 544 million years ago3) next smaller division of geologic time after the period; is characterized by differences in life forms that may vary geolically4) middle era of earths history, during which Pangea broke apart, dinosaurs appeared, and reptiles and gymnosperms were the dominant life forms5) era of ancient life which began about 544 million years ago, when organisms developed hard parts, and ended with mass extinctions about 245 million years ago10) third longest division of geologic time is subdivided into epochs and is characterized by the types of life that existed worldwide14) longest subdivision in the geologic time scale that is based on the abundance of certain types of fossils and is subdivided into eras, periods, and epochs Across: 2) large, ancient landmass that was composed of all the continents joined together6) second longest division of geologic time; is subdivided into periods and is based on major worldwide changes in types of fossils 7) era of recent life that began about 66 million years ago and continues today; includes the first appearance of Homo Sapiens about 400,000 years ago8) organism with a three lobed exoskeleton that was abundant in Paleozoic oceans and is considered to be an index fossil9) change of organisms over geologic time 11) chlorophyll containing, photosynthetic bacteria thought to be one of Earth's earliest life forms12) group of organisms that reproduce only with other members of their own group13) process by which organisms that are suited to a particular environment are better able to survive and reproduce than organisms that are not
 

 

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