Question

cave ecosystems are characterized by extremely low light levels. what role does photosynthesis play in a cave ecosystem

1: Photosynthesis is essential because it provides the original energy source for all food chains in this ecosystem.
2: photosynthesis is essential only for those organisms that must travel outside of this ecosystem to acquire food.
3: photosynthesis is optional because some organisms use sources inside the outside of this ecosystem for food.
4: photosynthesis is not needed since organisms have adapted to live in the dark where photosynthesis cannot take place.