1. To support the hypothesis that hydrogen and methane fostered the emergence of life on Earth, the passage mentions the
(A) concentrations of these gases in Earth's early atmosphere
(B) discharge of sparks through gases around hydrothermal vents
(C) likely composition of the early Earth's seafloor(D) temperature and alkalinity of the seawater on ancient Earth
(E) chemical reactions of seawater with energy-rich gases
In order to prove this hypothesis we first hear about the experiment conducted in 1952. But the experiement alone has a flaw ( such high concentration of gases are not seen on earth ). Again to support the hypothesis the idea that pre historic sea floor contained peridotite is introduced. Hence option C is correct.Seawater reacts with the peridotite, producing energy-rich gases such as hydrogen and methane. Some scientists speculate that these gases could have fostered the emergence of life on Earth. A famous experiment conducted in 1952 showed that sparks discharging through energy-rich gases produce many organic compounds, including amino acids, which are components of all living things.
However, geologists later concluded that these gases were probably not concentrated enough in Earth's early atmosphere to form such compounds.
But the gases are far more concentrated in the Lost City waters. Billions of years ago, could vents resembling those at Lost City have produced the organic compounds required for life? Hydrothermal fluids at Lost City contain certain organic compounds. And on early Earth, peridotite probably comprised most of the seafloor, making conditions like those at Lost City far more common than they are today.2. The passage indicates that most current hydrothermal vents
(A) teem with methanogens and similar microbes - No mention
(B) are not found on undersea beds of peridotite - True implied that unlike (most: implied) other vents lost city lies around peridotite(C) have natural chimneys that vent acidic seawater - the water around them is acidic we dont know what they vent out
(D) produce organic compounds such as amino acids - No mention
(E) generate hydrogen and methane at high temperatures - It has high temperatures ( but do they release H2 and CH4 ? like they do in lost city )
Around most hydrothermal vents, the seawater is extremely acidic and reaches temperatures over 400 degrees Celsius. But at Lost City, the water is alkaline and no hotter than 90 degrees Celsius. And unlike other hydrothermal vents, those at Lost City are situated on seafloor consisting mainly of rock called peridotite. Seawater reacts with the peridotite, producing energy-rich gases such as hydrogen and methane.3. The passage most clearly implies that some of the microbes at Lost City may
(A) use methane generated by geothermal reactions to support their metabolic processes
(B) descend from extraterrestrial life-forms that originated billions of years ago
(C) consume certain organic compounds found in hydrothermal fluids within natural chimneys
(D) be able to withstand the acidic seawater and extreme temperatures found around most other hydrothermal vents
(E) have biochemical pathways that first appeared among primordial life forms billions of years ago - true, these biochem pathways were inherited by their present ancestors Each step in the geothermal process that generates methane is replicated in the biochemical pathways of these methanogens. This suggests that on early Earth, the methanogens' primordial ancestors at sites like Lost City may have simply co-opted each of the geochemical steps for themselves, producing the first biochemical pathways, which their descendents have inherited.4. The question asked in the third paragraph (see highlighted text in red) serves mainly to
(A) suggest a hypothesis that the other sentences in the third paragraph help support - keep, passage is about proving the hypothesis about how life emerged(B) raise doubts about a hypothesis stated explicitly in the second paragraph - Wrong, the question is unrelated to the hypothesis - 'Some scientists speculate that these gases could have fostered the emergence of life on Earth'. To question this hypothesis we need to provide support or question the fact life can't emerge in H2 and CH4.
(C) rhetorically imply that the main conclusion of the passage as a whole needs additional support - Wrong, Trick question
It rhetorically questions the main conclusion of the passage that 'life emerged from thermal vents' but it doesn't rhetorically says that 'the main conclusion of the passage as a whole needs additional support'.
The passage has already provided a lot of additional supports to prove the main hypothesis.(D) indirectly help explain the presence of the geothermal process discussed in the fourth paragraph - Wrong, it's a question that doesn't explain the presence of geothermal process in the organisms present in Lost City vents
(E) indicate the issue that most strongly motivated Kelley to lead her expedition to analyze Lost City - Wrong, We don't know what was Kelly's actual goals