Deep-Sea Life Without Sunlight

Activities to try

1. 1

   Build a vent food web on a different power source

   Why it works: Photosynthesis is not the only way to build a food web. Producers do the same job — making food by fixing carbon from CO2 — but can be powered either by light (photosynthesis) or by chemical energy from oxidising H2S (chemosynthesis). Bacteria, not green plants, are the producers at a vent, and the community's energy source is chemical, not the Sun.

   1. First build (or label) a familiar sunlit web: Sun → phytoplankton/plants → consumers, and mark where the energy enters.
   2. Now build a hydrothermal-vent food web set in permanent darkness. Try to place the Sun at the base and notice it cannot power this web — no sunlight reaches kilometres down.
   3. Choose the base's actual energy source from options including 'sunlight', 'the vent's heat', and 'chemical energy (oxidising hydrogen sulphide, H2S)'. Select the chemical-energy option so chemoautotrophic bacteria become the producers.
   4. Extend the web: bacteria → tube worms / giant clams → vent crabs, and trace the energy flow from the chemical source upward.
   5. Set the two webs side by side and fill a comparison table: inputs, energy source, and product (food/organic matter from CO2) for photosynthesis vs chemosynthesis.
2. 2

   Reason with an astrobiologist: did life begin at vents, and where else might it be?

   Why it works: Vents reshape the search for life because they show a food web can run on chemical energy and water rather than light. Whether life began at vents, and whether ocean moons host life, are genuine open scientific questions to be argued from evidence and uncertainty — not settled facts.

   1. Take on the question in role: ask and answer 'Why look at hydrothermal vents to search for life beyond Earth?' and 'Could life have begun at vents?'
   2. Set out the reasoning: if life needs chemical energy, water and minerals — which vents supply without sunlight as the energy source — then sunless environments elsewhere are not automatically lifeless.
   3. Apply the analogy to Europa and Enceladus: these icy moons may have subsurface oceans and hydrothermal chemistry but no sunlight; discuss what makes them candidates and what remains unknown.
   4. State explicitly which parts are established (vent communities exist and run without sunlight as their energy source) and which are open hypotheses (origin of life at vents; life on ocean moons).
   5. Weigh at least one piece of evidence for and one source of uncertainty before giving a tentative, reasoned position.
3. 3

   Explore and interrogate a vent cross-section

   Why it works: A vent community is a complete food web whose base producers are bacteria powered by chemical energy, with no sunlight as the energy source; the same comparison that defines photosynthesis clarifies how chemosynthesis differs.

   1. Explore a labelled vent scene: mineral-rich fluid rising, bacterial mats, tube worms, giant clams and vent crabs — tracing which organism depends on which.
   2. Open a photosynthesis/chemosynthesis comparison showing inputs, energy source and product aligned for each.
   3. Examine an Earth-vent ↔ Europa/Enceladus analogue panel and state what the two settings share.
   4. Answer short checks: name the producer at a vent; name its energy source (oxidising H2S) and its carbon source (CO2); and explain why the community survives with no sunlight as its energy source.