The Tower bridge has 2 levels so that pedestrians can use the upper level while

Build a market-oriented economy;

Conditions are more like living on  land  for creatures in the upper part of the intertidal, which is only covered with  water  at extreme high tide, so life is easier on land. conditions are more like living in the ocean for creatures in the lower part of the intertidal which is only exposed to air at extreme low tide. so basically it both worlds of land and ocean.

  troposphere hope i u have a good day