Life is every where

     I made the kids walk up and down the beach today and not go into the water for the sole purpose of looking at life  They were reluctant at first and whiny but by the end were turning over rocks and digging in the sand. We found 3 different types of crab. Sand Dollars. Little surface skimmers with conical shells about a centimeter long. A weird purple jelly fishy thing that we named the Sea Mushroom. We found a big old oyster shell with at least two other kinds of creatures living on its shell.
      I wonder what is the limit for things living on other things. Bacteria on bacteria on parasites on little creatures on bigger creatures, How many layers are supported?