What is the difference of the atomic masses of the heaviest and lightest elements in the table?

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

What organelle other than the nucleus houses dna in a eukaryotic cell?

Several bird species feed in a certain species of tree. each bird species feeds in a different part of the tree. which statement is true of these bird species? a. they have adapted to different niches due to competition b. they have a carnivorous relationship with the tree species. c. they have adapted to different niches due to predation d. they have a symbiotic relationship with the tree species.