The correct order of the geologic eras, from most ancient to most recent, is __________.

Many researchers now believe that the first self-replicating molecules were __________.

A radioactive isotope has a half-life of 1.2 billion years. As measured by the presence of the isotope and its stable decay product, a rock originally contained 10 grams of the radioactive isotope and now contains 1.25 grams. Approximately how many years old is the rock?

You are watching a movie in which one of the characters excitedly claims to have found human remains in Asia dated at 10 million years old. The date was obtained by carbon-14 dating. What is your reaction?

Single-celled prokaryotes had Earth to themselves for approximately __________.

Ancient cyanobacteria were very important in the history of life because they __________.

What prokaryotic adaptation occurred during the oxygen revolution and opened up the possibility for energy-demanding multicellular life-forms?

What evidence supports the hypothesis that mitochondria and plastids evolved from prokaryotic endosymbionts?

Prior to the Cambrian explosion, most animals were small and soft-bodied. What development appears to have spurred adaptations such as sharp spines, claws, and body armor (shells)?