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