Chapter 18

An abundance of ___ in Earth's early armpsphere would have prevented the spontancous assembly of organic compounds on early Earth. a. hydrogen b. methane c. oxygen d. nitrogen

The first interval of Earth's existence is called the ___ a. Cambrian b. Hadean eon c. Proterozoic eon d. Archean eon

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

Miller and Urey created a reaction chamber that simulated conditions in Earth's early atmosphere to test the hypothesis that ___. a. lightning-fueled atmospheric 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

RNA in ribosomes catalyzes formation of peptide bonds in all organisms. This supports the hypothesis that ____. a. RNA can hold more information than DNA b. RNA is more stable than DNA c. an RNA world existed prior to the rise of DNA d. proteins evolved before RNA

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

Photosynthesis carried out by one group of ___ resulted in Earth's first increase in atmospheric oxygen levels. a. archaea c. protists b. bacteria d. algac

Mitochondria are most closely related to ___ a. archaea c. rickettsias b. cyanobacteria d. algae

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 c. DNA b. lipids d. RNA

A rise in oxygen in Earth's air and seas set the stage for the evolution of ___ a. aerobic respiration c. photosynthesis b. fermentation d. sexual reproduction

Which of the following was not present by the end of the Precambrian? a. archaea c. fungi b. bacteria d. fish

The first chloroplasts evolved from ____. a. archaea c. cyanobacteria b. aerobic bacteria d. early eukaryotes

During the Precambrian, ___ a. atmospheric oxygen concentration declined b. bacteria, archaea, and early eukaryotes arose c. dinosaurs became extinct d. all of the above

Arrange these events in order of occurrence, with 1 being the earliest and 6 the most recent. $$ \text { 1 } \quad \quad\quad\quad\quad \text { a. Earths first seas form } $$ $$ \text { 2 } \quad \quad\quad\quad\quad \text { b. origin of mitochondria } $$ $$ \text { 3 } \quad \quad\quad\quad\quad \text { c. first protocells form } $$ $$ \text { 4 } \quad \quad\quad\quad\quad \text { d. Precambrian ends } $$ $$ \text { 5 } \quad \quad\quad\quad\quad \text { e. origin of chloroplasts } $$ $$ \text { 6 } \quad \quad\quad\quad\quad \text { f. first animals appear } $$