24. History of Life on Earth

Why is the four-stage hypothesis for the abiotic origin of life useful?

The early atmosphere on Earth is thought to have lacked which of the following gases?

Currently scientists think the early atmosphere probably consisted of __________.

The Miller and Urey abiotic synthesis experiment (and subsequent, similar experiments) showed that __________.

The early atmosphere may not have been as reducing as originally postulated by Haldane, Oparin, Miller, and Urey. In light of current thinking about the composition of the early atmosphere, what is regarded as a likely place for the abiotic synthesis of organic molecules to have occurred?

Abiotically produced vesicles display which of the following rudimentary qualities necessary for life?

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 __________.

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

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)?