Many cave communities will rely on food being brought into the cave from the surface. This organic debris includes leafs, twigs etc. brought in by surface streams or falling down vertical shafts; it also includes organic matter brought in by visitors to the cave, carcasses of animals that have wandered in, and droppings from animals such as bats. The amount of debris that can be brought in is very evident in Porth yr Ogof - including large tree trunks. Most creatures will be found near the surface where food is more plentiful - the deeper you go in a cave the harder you will have to look. In the depths of a cave the communities may be concentrated around food sources generated by cave bacteria on e.g. flowstone.

Click on the subtitles to the left to find out more about the variety of life to be found underground. The organisms have been roughly divided up according to their classification with the simplest organisms at the beginning and the more advanced at the end.