1. 1 19.1 How Did Life Begin? I. ________________ were the first to evolve A. ______ billion year old _____________ fossils have been found 1. ____________ – no internal compartments B. ____________________ 1. ______________ – releases oxygen into atmosphere a. took millions and millions of years but today _______ of atmosphere is oxygen C. Maybe the ancestors of _______________ and/or ___________________

2. 2 II. Two _______________ of bacteria A. ____________ – cause disease and decay B. ____________ – can produce energy without _________ (combine hydrogen with carbon dioxide = ____________) 1. Most likely the ancestor of all modern _______________ cells III. Dawn of the ___________________ A. Over 1 _____________ yrs. bacteria were the only __________ things on earth B. About ______ billion years ago 1st eukaryotes appear C. ___________ – 1st eukaryotes, had membrane bound ______________ 1. Some were _____________ while others hunted __________

3. 3 IV. ______________ evolution A. First fossil of multicellular organism _______ million yrs. old B. Multicellular protists evolved into ____ different kingdoms 1. _________,__________,__________ V. ___________ Period – 600 mya to 500 mya A. All major groups, except _________, originated during this time B. Life was more __________ in the _____ than it has ever been since

4. 4 VI. Mass ____________ A. About 440 mya the 1st of ____ major mass _____________ occurred 1. ______ mya 2 nd 2. ______ mya 3rd (96% of all species extinct) 3. ______ mya 4 th 4. _____ mya 5th (2/3 of all land species extinct including dinosaurs extinct) B. Another mass ___________ may be on the way