1. What system comprise humans, plants, and animals?
A. abiotic components of the ecosystem
B. biotic components of the ecosystem
C. microorganisms in the ecosystem
D. parasites in the ecosystem

2. what does "mutualism" mean?
A. one organism benefitted while the other is harmed.
B. one organism benefitted while the other is not effected.
C. both organisns are benefitted.
D. both organisms are harmed. ​