What was the history of life in North America? To answer this question, Kirk Johnson
, the Sant Director of the Smithsonian National Museum of Natural History, takes the viewer on an odyssey of time and space, from the original bacterial species that generated Earth’s oxygen atmosphere, through dinosaurs and their extinction, the emergence of mammals, and to the entrance of humans into North America. In this high interest video, the second episode of a three-part series, major events in the history of life on earth, and their relation to the North American continent, are discussed in a relevant and dramatic manner. Dr. Johnson conveys a sense of wonder and provides an enthusiastic introduction to mind expanding vistas of deep time and dramatic episodes in the story of earth’s life.
Dr. Johnson begins the discussion at a site in Utah, the Kaiparowitz Plateau rich in dinosaur discoveries such as Lythronax, the “King of Gore”. In the Bahamas, living examples of earth’s earliest fossil life, the algal, coral-like structures named stromatolites, can be found. These ancestral forms are likely responsible for pumping out earth’s oxygen atmosphere as a waste product of photosynthesis, the same process found in all green plants today. The evolution of complex life, from invertebrates, through fishes, reptiles, and dinosaurs is highlighted with visits to sites such as Monument Rock in Kansas, where the fossil of a fourteen-foot carnivorous fish, Xiphactinus, was found by local fossil hunters, to a plateau in Colorado, now nearly one mile in elevation, where the fossils of ocean invertebrates, the spiral-shaped ammonites, can be found today as basins known locally as “bird baths”. At a site in North Dakota, Dr. Johnson unearths a rock layer containing glass beads and “shocked quartz”, evidence that an asteroid the size of Mt. Everest struck the earth 66 million years ago unleashing the energy equivalent of one billion atomic bombs, and likely causing the extinction of the dinosaurs. The death and destruction of the dinosaurs provided an opportunity for the early mammals to take their places and later dominate the earth. 48 million years ago, North America was covered with tropical forests rich in primate species, but a change in climate led to cooling and the disappearance of North American primates until, just 14,000 years ago, a certain two-legged primate entered North America, the ancestors of today’s Native Americans.
The PDF contains a two-sided video worksheet consisting of 40 multiple choice and true-or-false questions, and a sorting question whereby the students place the events in the history of North American life in order from the beginning to the present. The PDF also includes an answer key and an MS Word download link. You will need to obtain a DVD of the video, use the PBS Internet site, or YouTube