Answer:
-toxins
-predator vs prey relationship
-competition
-New Habitat
-Disasters
Well thats ur opinion some people might not think it is hard
Second messenger systems: The amino acid-derived hormones epinephrine and norepinephrine bind to beta-adrenergic receptors on the plasma membrane of cells. Hormone binding to receptor activates a G protein, which in turn activates adenylyl cyclase, converting ATP to cAMP.
I think it's the first one but I'm not sure
The Answer is D Decomposers. Hope this helps!