chunjuwu wrote:
It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So, even if bacteria did arrive on Earth from Mars, they must have died out.
The argument is most vulnerable to which of the following criticisms?
(A) It fails to establish whether bacteria actually developed on Mars
(B) it fails to establish how likely it is that Martian bacteria were transported to Earth
(C) It fails to consider whether there were means other than meteorites by which Martian bacteria could have been carried to Earth.
(D) It fails to consider whether all bacteria now on Earth could have arisen from transported Martian bacteria.
(E) It fails to consider whether there could have been strains of bacteria that originated on Earth and later died out.
Note: There are two questions available with the similar stimulus and same first line but different question. The other question (complete the passage) is discussed in: https://gmatclub.com/forum/it-is-theoret ... 46449.htmlBacteria may have developed on Mars early in its history and some may have been carried to Earth by a meteorite.
However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time
No two bacterial strains on Earth are different enough to have arisen on different planets.
Conclusion: Even if bacteria did arrive on Earth from Mars, they must have died out.
Assuming everything given in premises is true, can we conclude that "even if bacteria did arrive on Earth from Mars, they must have died out." What is the flaw in concluding this?
If bacteria did arrive on Earth from Mars, can we say that they must have died out only because current set of bacteria on Earth have not originated on two different planets? No. What if the entire set currently on Earth came from the bacteria that arrived from Mars? Then, if bacteria did arrive from Mars, it may not have died out. It may have proliferated on Earth and that is what we have today. But the argument fails to consider this point.
Hence (D) is correct.
(A) It fails to establish whether bacteria actually developed on Mars
The argument does mention that bacteria could have developed on Mars.
(B) it fails to establish how likely it is that Martian bacteria were transported to Earth
How likely is irrelevant. The argument says that
if bacteria came to Earth from Mars, it died out.
(C) It fails to consider whether there were means other than meteorites by which Martian bacteria could have been carried to Earth.
Irrelevant
(E) It fails to consider whether there could have been strains of bacteria that originated on Earth and later died out.
The conclusion is about what happened to the strains of bacteria that originated on Mars. The conclusion is that Mars bacteria died out.
The argument doesn't say whether there were strains of bacteria that developed on Earth and later died out. Note that though it seems just the flip way of saying what (D) says, it isn't. The argument does not need to consider that there could have been strains of bacteria that originated on Earth and later died. It is possible that no bacteria originated on Earth. So the shortcoming of the argument is not that is failed to consider that Earth bacteria died, but that it failed to consider that all current bacteria could have come from Mars. Whether bacteria originated on Earth too but died or whether they never originated on Earth is irrelevant.
Answer (D)
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24 Jul 2019, 09:31
