As energy flows from producers to consumers, some E is lost to the
environment as

you know they are heterozygous for a trait because they have it as jj or jj.

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.