P416 Comparative Animal Physiology Fall Semester, 2005 Dr. Michael S. Finkler

Much of What You Will Learn in This Course Will Someday Prove to Be Incorrect Scientific discovery is limited by what can be perceived. Always a chance that an idea is incorrect. –hypotheses and theories –No such thing as a scientific fact Scientific knowledge is constantly revised as new insights into natural phenomena are gained. Scientists must maintain a healthy skepticism and an open mind.

What is Physiology? The study of biological function

Physiology is the study of how a living organism stays alive A difficult task! –Living organisms have complex, organized structures –Second Law of Thermodynamics: Degree of disorder in the universe can only INCREASE Living organisms must maintain order in a universe that tends to move towards disorder.

How does a living organism stay alive? Living organisms maintain order inside their bodies (the “internal environment”) by increasing disorder in the external environment Maintenance of constant conditions in the internal environment necessary for order (life) to be maintained.

Homeostasis State of constancy within the internal environment of a living organism A dynamic process –constant adjustment to counteract changes Central principle of physiology

How does an organism maintain homeostasis? Regulation –maintaining different attributes of the internal environment at relatively constant levels –Requires a regulatory mechanism: Sensor - Detects changes (disturbances) in the internal environment Effector - Performs an activity that compensates for the change Controller/Integrator - controls activity of the effector based on information from the sensor

Regulatory Mechanisms Work by Feedback Feedback = return of output to the input part of a system The response of the effector influences subsequent output by the effector

Types of Feedback Negative Feedback –activity of effectors opposes any deviation of the controlled variable from the regulated level –most common type in biology Positive Feedback –activity of effectors enhances deviation of controlled variable from the regulated level –rare in biological systems, and always part of a larger negative feedback system

Comparative Physiology Compares physiological functions between species to discern physiological and evolutionary patterns

Subdisciplines Ecological Physiology –a.k.a. Environmental Physiology, Physiological Ecology –examines adaptations of organisms to their environment Evolutionary Physiology –seeks understanding of evolutionary relationships based on physiological attributes

Adaptation Evolution through natural selection leading to an organism whose physiology, anatomy and behavior are matched to the demands of its environment. A slow process, over multiple generations Central topic of comparative animal physiology

Adaptation is Sometimes Confused With: Acclimatization –physiological/biochemical/anatomical change in an individual organism resulting to chronic exposure to new conditions in the natural environment Acclimation –similar changes induced in laboratory settings

Differences Acclimation/Acclimatization changes occur in an individual changes are generally reversible Adaptation changes occur over multiple generations changes not generally reversible

A Characteristic is Adaptive If: It confers a maximal probability of survival and successful reproduction in comparison with available alternative states. Qualifiers: –Characters are adaptive only in specific environmental contexts. –Adaptive  optimum

Adaptive Approaches to Environmental Change 1.Tolerance (Conformity) –Increase degree of tolerance to adverse conditions (decreased maintenance of homeostasis). 2.Opposition (Active Resistance) –Increase activity of regulatory mechanisms to maintain homeostasis at tight levels. 3.Evasion (Escape) –Avoid change in conditions (behavioral) The alternative = Death (Failure) – not usually very adaptive