Chapter 18

An abundance of __________ in the atmosphere would have prevented the spontaneous (abiotic) assembly of organic compounds on the early Earth. a. hydrogen b. methane c. oxygen d.nitrogen

The prevalence of iron-sulfide cofactors in living organisms may be evidence that life arose ___________. a. in outer space c. near deep-sea vents b. on tidal flats d. in the upper atmosphere

The evolution of _________ resulted in an increase in the levels of atmospheric oxygen. a. sexual reproduction b. aerobic respiration c. the noncyclic pathway of photosynthesis d. the cyclic pathway of photosynthesis

Mitochondria may be descended from ______________. a. chloroplasts c. early protists b. bacteria d. archaea

Chronologically arrange the evolutionary events, with 1 being the earliest and 6 the most recent. ___1 ___2 ___ 3 ___ 4 ___ 5 ___ 6 a. emergence of the noncyclic pathway of photosynthesis b. origin of mitochondria c. origin of proto-cells d. emergence of the cyclic pathway of photosynthesis e. origin of chloroplasts f. the big bang