After feeding at the surface of the ocean during
the day, many ocean organisms migrate to deeper
waters. While there, they release ammonia in
their urine. Many bacteria use the nitrogen from
the ammonia as they make amino acids, which
eventually end up in food chains on both land
and water. These amino acids may even be used
in humans. Which statement best explains these
observations?
(1) Chemical elements, including nitrogen, pass
through food webs and are combined and
recombined in different ways.
(2) Chemical elements, including nitrogen, are
removed from food webs and eliminated
from ecosystems.
(3) Nitrogen is transferred directly from bacteria
to humans.
(4) All elements in the ocean remain there and
are not transferred to other ecosystems.