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.

3 answers

I disagree.

http://science.howstuffworks.com/life/biology-fields/cave-biology3.htm

Oh. So is it 1?

Yes.