Bio Ch 15 Test Review Part 1/2

The earliest discovered fossils are of ________ dating back to ________ years ago.

• algae; 1 billion

• prokaryotes; 3.5 billion

• fish; 600 million

• single-celled eukaryotes; 4.5 billion

Which highly reactive gas was probably absent from the Earth's primitive atmosphere?

• oxygen

• water vapor

• carbon dioxide

• methane

What was the probable role of oxygen gas in the early stages of life's appearance on Earth?

• Cellular respiration, which depends on oxygen availability, provided abundant energy to the first life-forms.

• Oxygen promoted the formation of complex organic molecules through physical processes.

• Abundant atmospheric oxygen would have created an ozone layer, which would have blocked out ultraviolet light and thereby protected the earliest life-forms.

• Oxygen gas tends to disrupt organic molecules, so its absence promoted the formation and stability of complex organic molecules on the early Earth.

Miller-type experiments have shown that

• given the conditions of early Earth, the formation of life would still require additional materials from meteorites and asteroids.

• complex organic molecules can be produced by physical processes from inorganic components.

• living cells could survive in primitive Earth's atmosphere.

• simple cells can be produced in the laboratory using a "soup" of small organic molecules.

Which environment is thought to have promoted the dehydration synthesis of polypeptides and other macromolecules from smaller organic monomers on a prebiotic Earth?

• deep-sea hydrothermal vents

• sediments at the bottom of the world's oceans

• freshwater swamps and marshes

• hot sand, clay, or rock along the seashore

A current leading hypothesis about the first system of inheritance in the earliest life-forms involves

• self-replicating RNA molecules aided by ribozymes.

• self-replicating DNA molecules. 

• self-replicating polypeptides aided by ribosomes.

• proteins that served as templates for RNA molecules, leading to the formation of DNA.

RNA molecules that can function like enzymes are called ___.

Which list includes major events in the history of life on Earth in the proper order, from earliest to most recent?

• first prokaryotes, photosynthesis, colonization of land by plants and fungi, first eukaryotes

• first prokaryotes, first eukaryotes, photosynthesis, colonization of land by plants and fungi

• first eukaryotes, photosynthesis, colonization of land by plants and fungi, first prokaryotes

• first prokaryotes, photosynthesis, first eukaryotes, colonization of land by plants and fungi

The technique called radiometric dating is based on

• the assumption that radioactive isotopes accumulate in fossils at a constant rate.

• the use of fossils of known age to determine how fast carbon-14 decays.

• the formation of radioactive molecules in rocks after they are deposited.

• the steady, clocklike decay of certain radioactive isotopes over time.

The 14C:12C ratio can be used to date fossils that are up to approximately how old?

• 100 million years

• 7 million years

• 7,500 years

• 75,000 years