In 2010, the National Aeronautics and Space Administration (NASA) discovered a new species of bacteria, called the GFAJ-1 strain, that for a while promised to change our understanding of how living things survive. Deep in the waters of Mono Lake in California, NASA scientists discovered a form of bacteria that seemed to use arsenic, plentiful in its habitat, to make DNA and proteins. Most life forms are made from six main building blocks: carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Arsenic is toxic to most known organisms, but the GFAJ-1 strain can tolerate high concentrations of arsenic, and initial studies suggested that it could even incorporate the chemical into its cells. Some scientists claimed that this discovery had opened new possibilities for life elsewhere in the universe, as the existence of such a microbe would show that organisms can exist in chemical environments that scientists may not have considered.

Which of the following statements best summarizes the passage?

(A) The presence of arsenic-based bacteria would prove that there is life on other planets.
(B) Scientists have discovered that arsenic is not toxic to most known organisms.
(C) Claims made about the GFAJ-1 strain challenged scientists' perception of how living organisms survive.
(D) If GFAJ-1 were established as using arsenic to build its DNA, scientists would need to consider adding this element to the six main building blocks of life.
(E) The ecosystem of Mono Lake is a scientific phenomenon that scientists will be studying for years.





According to the information in the passage, upon discovery of the GFAJ-1 strain, some scientists believed it was

(A) a water-based bacteria that had a high tolerance for toxins
(B) one of the six building blocks of life
(C) a form of arsenic that was toxic to most living organisms
(D) a strain of bacteria that incorporated arsenic into its cells
(E) a form of DNA that did not need phosphorus to grow



Consider each of the following choices separately and select all that apply.

Based on the information in the passage, what reasonable conclusions can be drawn?

(A) If a species of bacteria can use arsenic in cell development, it is possible that planets that have high levels of arsenic might be able to support living organisms.
(B) If the GFAJ-1 strain's chemical processes do not follow the same patterns as those of other organisms, the strain must have originated on another planet.
(C) If scientists have discovered a living organism that uses arsenic in place of one of the six building blocks of life, it is possible that there may be other chemicals in addition to arsenic that can support life.