Chapter 18

An abundance of _____ in Earth’s early atmosphere would have prevented the spontaneous assembly of organic compounds on early Earth. a. hydrogen b. methane c. oxygen d. nitrogen

Miller and Urey created a reaction chamber that simulated conditions in Earth’s early atmosphere to test the hypothesis that _____. a. lightning-fueled atmopheric reactions could have produced organic compounds b. meteorites contain organic compounds c. organic compounds form at hydrothermal vents d. oxygen prevents formation of organic compounds

The prevalence of iron–sulfur cofactors in organisms supports the hypothesis that life arose _____. a. in outer space c. near deep-sea vents b. on tidal flats d. in the upper atmosphere

RNA in ribosomes catalyzes formation of peptide bonds in all organisms. This supports the hypothesis that _____. a. an RNA world existed prior to the rise of DNA b. RNA can hold more information than DNA c. only protists use RNA as their genetic material d. all of the above

By one hypothesis, clay _____. a. facilitated assembly of early polypeptides b. was present at hydrothermal vents c. provided energy for early metabolism d. served as an early genome

The evolution of _____ resulted in an increase in the levels of atmospheric oxygen. a. protocells b. the ozone layer c. oxygen-producing photosynthesis d. multicellular eukaryotes

Mitochondria most resemble _____. a. archaea c. cyanobacteria b. aerobic bacteria d. early eukaryotes

The presence of ozone in the upper atmosphere protects life from _____. a. free radicals c. viruses b. ultraviolet (UV) radiation d. ionizing radiation

A ribozyme consists of _____. a. clay b. DNA c. RNA d. lipids

A rise in oxygen in Earth’s air and seas put organisms that engaged in _____ at a selective advantage. a. aerobic respiration c. photosynthesis b. fermentation d. sexual reproduction

Which of the following was not present on Earth when chloroplasts first evolved? a. archaea c. protists b. bacteria d. animals

Chloroplasts most resemble _____. a. archaea c. cyanobacteria b. aerobic bacteria d. early eukaryotes

During the Precambrian, _____. a. protocells formed b. some bacteria evolved into mitochondria c. multicellular eukaryotes evolved d. all of the above

Arrange these events in order of occurrence, with 1 being the earliest and 6 the most recent _____ 1 _____ 2 _____ 3 _____ 4 _____ 5 _____ 6 a. water pools to form Earth's first seas b. origin of mitochondria c. first protocells form d. Precambrian ends e. origin of chloroplasts f. first animals appear