Educational Media Reviews Online

The lowly grasses form the focus of this DVD. The narrator reveals how significant the grass family has been on earth. Thirty to fifty million years ago there was a period of intense geological activity, resulting in the formation of mountain ranges and accelerating the process of erosion. The carbon dioxide that had resided in the air began to be combined with minerals in the sea to form limestone. The result was that, over millennia, the amount of carbon dioxide declined by five-sixths, causing a crisis in the plant kingdom. Trees, which had heretofore covered much of the planet when terrestrial climates were hotter than now, declined and were replaced by grasses, which had evolved cellular “pumps” that could extract more carbon dioxide from the air than trees could.

Grasses also evolved an ability to survive fires by sprouting after burns very quickly; the earth evolved rapidly from a forest-dominated to a prairies-dominated place. Some herbivores, among them species that later proved essential to humans, evolved an ability to break down the silica that grasses have in their leaves, and their numbers greatly increased, especially after the rise of mammals in the wake of the Cretaceous-Paleogene Boundary meteorite impact that dealt the coup de grace to the dinosaurs.

Once humans appeared on the ecological scene, they discovered, about ten thousand years ago, the ability to raise certain grasses as food, giving rise to agriculture. We profit from this discovery today; indeed, the survival of the human race largely depends now on the efficient production of foods like wheat, a grass.

Highly recommended for college students interested in biology in general and evolution in particular. Adults with a general knowledge of biological terms will enjoy this visually engaging DVD as well.