Though it has lost some biodiversity since being sealed 12 years ago, this terrarium has developed an interesting two-tiered world:
Currently the ecosystem is experiencing cycles. As the plant population increased, so did the isopods. This caused the isopod population to graze on a lot of the terrariums plants, causing the plant population to decrease. I imagine centipede populations may increase in future giving the plants the opportunity to recover. I found this terrarium very fascinating as it's almost as if there are two separate worlds within the same glass demijohn. The algae underground creates a unique habitat, which couldn't possibly exist in nature due to the fact the glass ensured that light could reach the soil underground. This allowed algaes, moss and fungi to flourish, alongside any of the smaller invertebrates that lived among them. Adult isopods seem to inhabit the surface and rarely venture below ground. I believe this is due to the hardness of the clay and rock substrate. The babies do seem to venture underground though, likely using tunnels left behind by earthworms many years ago.
This ecosphere is interesting because it includes an unintended plant variety:
Image: YouTube / Jartopia