Transcript p416 comparative animal physiology

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