Grand Challenges in Comparative Physiology: Integration Across Disciplines and Across Levels of Biological Organization

Schwenketal.(2009)providedanover-view of five major challenges in organ-ismal biology: (1) understanding theorganism’s role in organism–environ-ment linkages; (2) utilizing the func-tional diversity of organisms; (3)integrating living and physical systemsanalysis; (4) understanding howgenomes produce organisms; and (5)understanding how organisms walkthe tightrope between stability andchange. Subsequent ‘‘GrandChallenges’’ papers have expanded onthese topics from different viewpoints,including ecomechanics (Denny andHelmuth 2009), endocrinology(Denver et al. 2009), development ofadditional model organisms (Satterlieet al. 2009), and development oftheoretical and financial resources(Halanych and Goertzen 2009). This isthe sixth paper in the ‘‘GrandChallenges’’ series, which offers theview from comparative physiology.In this article, we expand upon threemajor challenges facing comparativephysiology in the 21st century: verticalintegration of physiological processesacross organizational levels within or-ganisms, horizontal integration ofphysiological processes across organ-isms within ecosystems, and temporalintegration of physiological pro-cesses during evolutionary change.‘‘Integration’’ is a key. It defines thescope of the challenges and must beconsidered in any solution. Reductiveand inductive approaches both havebeen used with great success in biology.The reductive approach employs a sim-plified system to study a complexprocess. There is no question thatsuch an approach has yielded a greaterunderstanding of the molecular mech-anismsofcellularprocesses.Theinduc-tive approach depends on observationto develop universal principles. CharlesDarwin, after all, used this approach todevelop the theory of natural selection.All too often these approaches areviewed as mutually exclusive, when, infact, they are complementary and areused, to varying extents, by most biol-ogists working today. Yet, we havefallen short of full integration acrossdisciplinesandlevelsofbiologicalorga-nization. A major impediment for fur-ther advancement has been thelimitations in tools and resources.However, recent technological ad-vances (e.g., systems biology) give usan opportunity to combine reductiveand inductive approaches to studyemergent properties (Boogerd et al.2007) and now allow us to entertain