The order from the longest to the largest will be; Eon, Era, Period, Epoch.
Eon is the longest division of geologic time. Epoch is the shortest division of geologic time, only present in Cenozoic Era. Era is the second longest division of time, marked by sweeping changes in the fossil record. Period is the time division which is longer than an epoch but shorter than an Era.
It helps there chance of survival. they depend on one another for ex sometimes a fish will eat stuff off a sharks teeth, or if is hungry it will just eat they fish
To me this Biome sounds like a Tropical Forest i may be wrong.