Transcript Animal Physiology, Chapter 1

Animal Physiology
Zool 4230
General objectives:
1. Gain factual knowledge
2. Learning fundamental principles, generalizations, or
theories
Study of physiology
Physiology is the study of life processes:
 How living systems work, from the molecular
level to organ systems and to the whole organism
 How the organism responds to physical activities
and to the environment around it, whether it is the
vacuum of space or the depths of the ocean
 How disease can affect living systems
 How the genome translates into function both
within the cell and the whole organism
Table 1.4
Introduction
• Comparative physiology
• Environmental physiology
• Evolutionary physiology
Figure 1.17 The comparative method
Figure 1.12 Performance in an oxygen-poor environment
Migrating Pacific salmon
Survival need
• Goal- to maintain life
• Need
– Nutrients
– Oxygen
– Water
– Maintain body temperature
– Atmospheric pressue
Figure 1.1 The study of physiology integrates knowledge at all levels of organization (Part 1)
Figure 1.1 The study of physiology integrates knowledge at all levels of organization (Part 2)
Physiology’s two central questions
• Origin– why do modern-day animals
possess the mechanisms they have?
• Mechanism– how do modern-day animals
carry out their functions?
The Study of Origin
• Why do modern-day animals possess the
mechanism they have?
– Products of evolution
– The study of evolutionary origins reveals the
significance of mechanisms
– Reliance on indirect reasoning– very rarely
understood
Key process of evolutionary origin
• Natural selection- increase in frequency of
genes that produce phenotypes that
improves an animal’s chances of survival
and reproduction within the environment
• Adaptations- aid the survival and
reproduction
• Adaptive significance evolved by natural
selection
Figure 1.4 Structures similar in performance & adaptive significance can differ dramatically (Part 1)
Figure 1.4 Structures similar in performance & adaptive significance can differ dramatically (Part 2)
Natural selection
Two basic concepts
• Fitness– link to adaptation
• Environment– habitat
– Biome: problems encounter
– Design and strategy
– Behavioral modification
Environmental components
•
Environmental Component
– Stress
•
•
Biotic– direct and indirect effects of other
organisms, e.g. competition
Abiotic– physical and chemical
– Magnitude of fluctuations
•
•
Long term– tsunami outcome
Short term– lunar or daily cycle
– Resource/energy availability
Figure 1.9 Fish around Antarctica spend their entire lives at body temperatures near –1.9°C
Figure 1.10 Butterfly biogeography
Figure 1.11 A thermophilic (“heat-loving”) lizard common in North American deserts
Adaptation
• Adaptation
– Traits observed– result of selection
– Natural selection adjusts the frequency of
genes that code for traits affecting fitness
– Short term compensatory changes
• Acclimation
• Acclimatization
Responses to changes in environmental conditions
• Responses to changes in environmental
conditions
– Avoidance
– Conformity
– Regulation
– Behavior
Conformity and regulation
• Two principal types of relations between
an animal’s internal and external
environment
• Conformity/regulation
– Conformity- an animal permits internal and
external conditions to be almost equal
– Regulation- an animal maintains internal
constancy with external variability
Figure 1.5 Conformity and regulation
Figure 1.6 Mixed conformity and regulation in a single species
Advantages and disadvantages of conformity and regulation
• Regulation- disadvantage– costs energy
• Regulation- advantage– permits cells to
function independently of outside condition
• Conformity- disadvantage- cells within the
body are subject to change when outside
condition changes
• Conformity- advantage– avoids energy
costs of maintaining organization
Responses to environmental change
• Acute response
• Chronic response
– Acclimation
– Acclimatization
• Evolutionary response
Figure 1.7 Heat acclimation in humans as measured by exercise endurance
Mechanisms of adaptation
• Molecular level
– Genes/DNA
• Any changes at the DNA level
– Changes in protein expression
• Core of adaptation
– Anything that controls protein properties and
degradation
Genotype and environmental interaction
Protein synthesis and degradation
• Control of gene expression
• Intracellular proteolytic mechanisms
– Degradation may occur
• In cytoplasm
• In endoplasamic reticulum
• Ubiquitin (marker protein)serves as degradation
signal
Six steps at which gene expression can be controlled
Activation of G protein by extracellular signal
Interaction of two G proteins with a single cAMP-producing adenyl cyclase, giving both stimulatory and inhibitory pathways
Extracellular control signals
• Growth factor
• Hormones
• Neurotransmitters
Size and scaling
• Body-size relations are important in
making prediction of the species’
physiological and morphological traits.
• Length, area, and volume
• Isometric scaling
• Allometric scaling
Figure 1.8 Length of gestation scales as a regular function of body size in mammals
Figure 1.18 Physiological variation among individuals of a species
Homeostasis
• Maintaining constancy of internal environment.
– Dynamic constancy.
• Within a certain normal range.
• Maintained by negative feedback loops.
• Regulatory mechanisms:
– Intrinsic:
• Within organ being regulated.
– Extrinsic:
• Outside of organ, such as nervous or hormonal systems.
• Negative feedback inhibition.
Feedback Loops
• Sensor:
– Detects deviation
from set point.
• Integrating center:
– Determines the
response.
• Effector:
– Produces the
response.
Negative Feedback
•
•
•
•
Defends the set point.
Reverses the deviation.
Produces change in opposite direction.
Examples:
– Insulin decreases plasma [glucose].
– Thermostat.
– Body temperature.
Negative Feedback
(continued)
Positive Feedback
• Action of effectors amplifies the
changes.
• Is in same direction as change.
• Examples:
– Oxytocin (parturition).
– Voltage gated Na+ channels
(depolarization).
Scientific Method
• Confidence in rational ability, honesty and
humility.
• Specific steps in scientific method:
– Formulate hypothesis:
• Observations.
– Testing the hypothesis:
• Quantitative measurements.
– Analyze results:
• Select valid statistical tests.
– Draw conclusion.