  Energy concepts are fundamental across the sciences, yet these concepts can
be fragmented along disciplinary boundaries, rather than integrated into a
coherent whole. To teach physics effectively to biology students, we need to
understand students' disciplinary perspectives. We present interview data from
an undergraduate student who displays multiple stances towards the concept of
energy. At times he views energy in macroscopic contexts as a separate entity
from energy in microscopic (particularly biological) contexts, while at other
times he uses macroscopic physics phenomena as productive analogies for
understanding energy in the microscopic biological context, and he reasons
about energy transformations between the microscopic and macroscopic scales.
This case study displays preliminary evidence for the context dependence of
students' ability to translate energy concepts across scientific disciplines.
This points to challenges that must be taken into account in developing
curricula for biology students that integrate physics and biology concepts.
