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Chapter 1

BIO270H1 Chapter Notes - Chapter 1: August Krogh, Phenotype, Homeostasis

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Chris Garside

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Chapter 1 – Introduction to Physiology Principles
- Physiology has implications for evolutionary change in genotype
Phenotype = morphology, physiology and behaviour
- Physiological processes obey laws of physics and chemistry
- Electrical laws  neurons and function of membrane
- Chemical laws  Temperature and physiological processes
- Physical laws  Body size and physiological processes
August Krogh Principle – Every biological problem has an organism that is best suited for
the study
Fick’s Laws of Diffusion:
1) Concentration, heat and pressure go from high to low
2) Amount diffused across surface is proportionate to area of surface and
inversely proportionate to distance it must diffuse
- Diffusion rapid across short distances and extremely slow over long distances
- Explains why larger animals need a circulatory system
- Temperature has a profound effect on all processes in all biological levels of organization
- Body size has effects on physiological processes
- Scaling relationships:
- Isometric  physiological change proportionate to body size
- Allometric  physiological change not proportionate to body size
- Form and function are connected
- Physiology = function
- Anatomy = form
- Convergent evolution – unrelated to taxa similar in phenotype
- Parallel evolution – evolved in same way in different lineages
Conformers – Ectotherms (less expensive) Ex. Reptiles
Regulators – Endotherms (more stable) Ex. mammals
- Body temperature ~ 37 degrees C regardless of external temperature
Allostasis Physiological systems must change activity to permit constancy of functions in
- Homeostasis through change
- Homostatically regulated at a new level
Set point – Preferred physiological state
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