Let us see how these five members relate to each other in the tree-trunk ecosystem.

1. Humidity is an abiotic factor. It provides moisture for the tree trunk to decay. Therefore, the tree-trunk is depending on the right humidity to help it decay.
2. The decaying trunk provides fertile grounds for tiny green plans to grow.
3. Tiny green plants become food for bugs and insects that live in and around the decaying tree-trunk.
4. Bugs and insects become yummy food for small animals like the frog who hangs around the tree-trunk.
5. And… the frog becomes dinner for the snake hiding under the trunk.

So there you go. You will now notice that if one member of the chain is taken out, the entire relationship will be affected. For example: if a fire burns out the tree-trunk, the insects will starve and die, and the frog will have no food, and the snake will have to go somewhere else to look for food. The ecosystem will be no more.