Chpt 25&26 Pre-test questions

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Miller and Urey’s experiments that attempted to recreate conditions on early Earth were significant because _____.

they showed that organic molecules such as amino acids could be produced from inorganic molecules – Miller and Urey showed that under conditions postulated to have existed on early Earth, it was possible to spontaneously form essential organic molecules.

Why do some scientists believe that RNA, rather than DNA, was the first genetic material?

RNA has both information storage and catalytic properties – RNA has been shown to catalyze certain reactions (as part of ribosomes, rRNA participates in the catalysis of the peptide bonds that form proteins). It can also store information and perform some self-replication.

Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.

4.5 billion years ago … 3.9 billion years ago – Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago.

The oldest fossils usually _____.

are found in the deepest strata – are found in the deepest strata

Radiometric dating _____.

allows us to indirectly date fossils up to billions of years old based on minerals in surrounding volcanic strata – By dating minerals in volcanic strata above and below the fossils, we can determine a reasonable age range for the fossils.

The earliest organisms were most likely _____.

prokaryotic – Prokaryotes originated a few hundred million years after Earth’s crust cooled and solidified.

The atmosphere of early Earth probably contained no O2 until the emergence of organisms that _____.

used water as an electron source for photosynthesis – Oxygen began to accumulate in the atmosphere due to the action of photosynthetic cyanobacteria.

How does continental drift affect living organisms?

– It causes climate change, which puts selective pressure on organisms. – It causes changes in habitats, such as when large amounts of shallow marine habitat were lost in the formation of Pangaea. – It may cause an increase or decrease in competition among different species. – It happens so slowly that it does not affect living organisms.

Evolution works by _____.

"tinkering" with existing structures. – Evolution, and in particular natural selection, can only select for the best available traits. Modifications to those traits are usually made in small, incremental steps, and new inventions are rare.

Which of the following taxonomic categories contains all the others listed here?

Class -Class includes all categories except phylum, kingdom, and domain.

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