Digital ACT Reading Practice Question #1563

According to the passage, how do adult giant tube worms (Riftia pachyptila) obtain nourishment? Passage Excerpt (Natural Science): Prior to the 1977 discovery of hydrothermal vents along the Galápagos Rift, biologists assumed that all complex metazoan life on Earth was fundamentally dependent on solar energy harnessed through photosynthetic chloroplasts. Submersible dives to 2,500 meters revealed a startling ecosystem flourishing in perpetual pitch darkness, sustained by towering mineral chimneys spewing superheated water laden with dissolved hydrogen sulfide (H2S). Rather than sunlight, these abyssal communities are underpinned by chemotrophic bacteria that oxidize hydrogen sulfide to synthesize organic carbon. Giant tube worms (Riftia pachyptila), lacking mouths, guts, or digestive tracts, harbor billions of these endosymbiotic bacteria inside a specialized vascular organ called a trophosome, exchanging metabolic waste for chemical nourishment.