The half-life of carbon-14 is 5,600 years. A fossil that has one-eighth the normal proportion of carbon-14 to carbon-12 is probably
A. 11,200 years old.
B. 16,800 years old.
C. 5,600 years old.
D. 22,400 years old.
E. 2,800 years old.
Answer: B
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Prokaryotes were split into two domains based on differences in ____
a. staining characteristics b. metabolic capabilities c. rRNA sequences d. cell membrane properties e. cell wall composition
Most species of Gram-positive bacteria are
a. photoautotrophic. b. photoheterotrophic. c. chemoautotrophic. d. chemoheterotrophic. e. photochemoautotrophic.
Research on conditions that are relatively new to human populations such as myopia, breast cancer, and obesity support the conclusion that ________
A) human populations have accumulated a number of mutations that have become fixed by genetic drift B) the changes in human lifestyle account for all of the increase in frequencies of these conditions C) these conditions are indeed "diseases of civilization" and are likely caused by the interaction between genes (genetic susceptibility) and novel environments D) these human conditions are mere artifacts of the way in which they have been evaluated
An increase in the amount of carbon dioxide in the body causes
A) a simultaneous increase in the amount of oxygen in the body. B) an increase in the pH of the blood. C) a decrease in the rate at which impulses are released from the respiratory center. D) slow, shallow breathing. E) a decrease in the pH of the cerebrospinal fluid.