Question

the deep - sea hydrothermal vent ecosystems are home to unique organisms such as the giant tube worm, riftia pachyptila. these creatures thrive in the extreme conditions of the ocean floor, where temperatures can exceed 300 degrees celsius and the pressure is immense. riftia pachyptila lacks a digestive system and relies on a symbiotic relationship with chemosynthetic bacteria—bacteria that convert the vents toxic hydrogen sulfide into organic molecules that nourish the worm—housed in its trophosome. marine biologist dr. cindy lee van dover has studied these symbiotic relationships extensively, revealing that the bacterias ability to thrive in such harsh conditions is due to specialized enzymes that can withstand high temperatures and pressures.
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what does the text most strongly suggest about the relationship between riftia pachyptila and its bacteria?
a riftia pachyptila does not have a symbiotic relation with other bacteria because they lack specialized enzymes that enable survival in extreme conditions.
b the bacteria are the primary source of hydrogen sulfide for riftia pachyptila.
c riftia pachyptila can survive without the bacteria if necessary by converting hydrogen sulfide on its own.
d the organic molecules produced by the bacteria are likely immediately usable by riftia pachyptila with minimal processing.

Explanation:

• Option A: The text says Riftia pachyptila has a symbiotic relationship with chemosynthetic bacteria, so A is wrong.
• Option B: The bacteria convert the vent's hydrogen sulfide, not that the bacteria are the source of hydrogen sulfide for the worm. So B is incorrect.
• Option C: The text states Riftia pachyptila lacks a digestive system and relies on the bacteria, so it can't survive without them by converting hydrogen sulfide on its own. C is wrong.
• Option D: The bacteria produce organic molecules that nourish the worm, and since the worm lacks a digestive system, the organic molecules are likely immediately usable with minimal processing. This matches the text.

Answer:

D. The organic molecules produced by the bacteria are likely immediately usable by Riftia pachyptila with minimal processing.