GED Science TestEarth and Space ScienceHard
A team of oceanographers is studying a deep-sea hydrothermal vent ecosystem. They observe unique organisms, such as giant tube worms and chemosynthetic bacteria, thriving in the complete absence of sunlight. What is the primary energy source that supports the food web in this environment?
- APhotosynthesis from surface waters
- BChemical reactions involving hydrogen sulfide
- CDecomposition of organic matter from above
- DGeothermal heat from volcanic activity
Show answer & explanationAnswer & explanation
Correct answer: B. Chemical reactions involving hydrogen sulfide
Hydrothermal vent ecosystems are supported by chemosynthesis, a process where organisms (primarily bacteria) use energy from chemical reactions, particularly the oxidation of hydrogen sulfide released from the vents, to produce organic matter.
Why the other options are wrong
- A. Photosynthesis requires sunlight, which is absent in the deep ocean.
- C. While some organic matter drifts down, it's insufficient to support the rich biomass observed at active vents; chemosynthesis is the foundation.
- D. Geothermal heat provides the ideal temperature for life and drives the chemical reactions, but the heat itself is not the direct energy source for organic matter production.
Chemosynthesis
The process by which certain organisms, primarily bacteria, produce organic compounds using energy derived from chemical reactions, rather than sunlight (photosynthesis).
- Occurs in environments without sunlight (e.g., deep-sea vents).
- Uses chemical energy (e.g., from hydrogen sulfide).
- Forms the base of unique food webs.
Memory trick: Chemicals Fuel Life Where Sun Can't Shine