Answer: ecosystems

AnswerCrossword Clue
ECOSYSTEMSCoral reefs, e.g.
ECOSYSTEMSEnvironmental units
ECOSYSTEMSThey're full of life
ECOSYSTEMSThey may be carefully balanced
ecosystemsECOSYSTEM, all the organisms in a particular region and the environment in which they live
ecosystemsA biological community of interacting organisms and their physical environment