How the Earth Turned Green ? A Brief 3.8?Billion?Year History of Plants : University of Chicago Press : 9780226069777 : 022606977X : 26 Sep 2014 : On this blue planet, long before pterodactyls took to the skies and tyrannosaurs prowled the continents, tiny green organisms populated the ancient oceans. Fossil and phylogenetic evidence suggests that chlorophyll, the green pigment responsible for coloring these organisms, has been in existence for some 85% of Earth's long history?that is, for roughly 3.5 billion years. In How the Earth Turned Green, Joseph E. Armstrong traces the history of these verdant organisms, which many would call plants, from their ancient beginnings to the diversity of green life that inhabits the Earth today. Using an evolutionary framework, How the Earth Turned Green addresses questions such as: Should all green organisms be considered plants? Why do these organisms look the way they do? How are they related to one another and to other chlorophyll-free organism