You control a nontoken Saproling and/or creature with changeling.
Steps
Activate Mycologist's second ability by sacrificing a nontoken Saproling or creature with changeling.
When the creature dies, Yedora triggers, returning the creature from your graveyard to the battlefield face down as a Forest land and as a 1/1 Saproling due to Life and Limb.
Resolve the Mycologist ability, causing you to gain 2 life.