Zircon crystals that form in molten magma are easily dated because they initially contain ____
a. no lead
b. no uranium
c. uranium but no lead
d. lead but no uranium
e. both lead and uranium
ANSWER: c
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Indicate whether the statement is true or false.
The simplest nervous system found in nature is the nerve net. An example of an organism that senses and responds to its environment with this ancient system would be
A. a jellyfish. B. a cockroach. C. an earthworm. D. a frog. E. a fiddler crab.
Which of the following is used to reduce or eliminate the source of an infection?
A. Destruction of an animal reservoir of the infectious agent B. Treatment of sewage to reduce water contamination C. Destruction of vectors by spraying insecticides D. All of the choices are used to reduce or eliminate the source of an infection.
A hypothetical restriction sequence is 5?-TCTAGA-3?. The palindromic sequence is 3?-________-5?
Fill in the blank(s) with correct word