Use these questions to test your understanding. If you get them wrong, you will be linked back to the relevant part of the notes. 

Be sure you study them thoroughly (don't just get a quick fix for your mistake) so your overall understanding is improved.

1. Life could not form in the first few hundred million years of the formation of the earth

     a. because the oceans were not yet salty enough.   

     b. because organic material had not yet arrived from outer space.

     c. life probably formed but the traces have been obliterated by geological processes.

     d. because the rapid bombardment of the earth by large bodies made it very hostile to life

     e. because not enough carbon had been carried onto the earth by comets.

2. The most critical aspects of life are

     a. sexual reproduction and being able to move

     b. to harness energy and to reproduce

     c. to grow cells and carry out photosynthesis

     d. to form amino acids

     e. to breathe oxygen and exhale carbon dioxide

3. The very first forms of life we have found

     a. have long since gone extinct

     b. are related to some surviving forms of life, though which has evolved substantially to a higher level

     c. have survived apparently unchanged as the ultimate "living fossils"

     d. are so primitive they do not have cells

     e. are similar to life found on Mars

4. Stanley Miller's experiment is famous because

     a. he showed that he could synthesize amino acids under conditions now believed to hold on the early Earth

     b. he was able to make RNA in the laboratory, showing how life reproduced

     c. a huge portion of the carbon in his chemicals - 15% - appeared as life-like sludge in his beaker

     d. although he had the wrong chemicals, he introduced the idea of trying to make chemical precursors to life in the laboratory

     e. he worked for a Nobel prize winning scientist.

5. Errors, or mutations, in the reproduction of early life

     a. were virtually non-existent, because the life forms were so simple

     b. were the underlying force for the development of improved life forms

     c. were the big problem in getting life started at all

     d. were a problem with RNA replication but did not occur any more when DNA developed

     e. occurred at a very high rate because of the high rate of radioactivity of the sun.

6. DNA replication carries the information for new organisms because

     a. DNA attracts and bonds specific nucleotides that only pair with other specific nucleotides in the DNA chain, producing a negative copy of itself

     b. DNA splits off a section of itself that grows into a copy like a lizard regenerating a lost tail

     c. the phosphates and sugars of the DNA copy each other to carry the information

     d. the DNA sends out RNA to the ribosomes with instructions on how to make new DNA

     e. the helical structure of DNA allows it to move through the cell quickly, making copies.

7. Mars is a high priority target for space exploration because

     a. we think there are intelligent Martians hiding from us there

     b. we want to build space colonies on it.

     c. it appears to have many of the conditions needed for life in its early history, so we might find signs that life formed

     d. the face on Mars suggests there is a dead civilization we might discover

     e. its huge mountains and canyons would be highly scenic.

8. Mars is an attractive place to look for early life forms because

    a. bacteria might have escaped from the early earth and colonized Mars

    b. it is on the edge of the sun's habitable zone - life might have formed when it still had oceans of water

    c. its red color might be from a primitive lichen

    d. we can see its surface better than for any other planet

    e. our spaceships have found materials under its surface the probably came from early life