an ecosystem (system of an ecological community and its environment)

caddisworm, caddis fly larva

accomplish, perform, fulfill

role

important, significant

importance, consequence, significance

ecology, mode of life of living creatures / way of life, the way people live

system, family / style

a bug, insect, worm / a serpent, snake / (figurative): a worm (person living for only one thing) / (derogatory): a worm (despicable person) / a temperament (thought which is in the deep in mind)

river, stream