1. Introduction to Bil 265 - Exams, reading, and grading policy.

2. The pillar of physiology!

• Homeostasis. The concept of homeostasis was first hinted at by one of the founders of the modern science of physiology, Claude Bernard (1813-1871), though the term "homeostasis" wasn't used until later. (Read the linked page on Claude Bernard thoroughly!) Physiological or chemical variables, such as temperature or concentration of a metabolite, vary little as compared with the external environment. Such regulation allows organisms to move from a favorable environment to a more hostile, changing environment. For short-lived organisms, such as those that follow "r-selected" life history strategies, a broad range of mechanisms for homeostasis might not be so important. But, for long-lived, "K-selected" organisms, such as ourselves, the ability to move and exploit hostile environments is critical. (Eckert, Fig. 1-2) (For a review of r and K selection, look at my page here.)

  Homeostasis is closely related to the physical concept of the steady state, where input and output rates for a process are closely regulated to as to maintain constant action of the process. For example, a candy bar is eaten. The output is the Carbon dioxide exhaled. Even though most people don't constantly eat candy bars (and other sources of food), blood glucose levels remain fairly constant - a steady state for glucose. The reason for this steady state is that excess glucose molecules are stored in the liver as glycogen, a polymer of glucose. Glucose storage and release into the blood stream is regulated so that under varying conditions of glucose use, the concentration of glucose remains roughly constant. If you eat a candy bar, of course blood glucose increases but very little. Glucose concentrations are almost steady. Physics shows us that entropy, a measure of disorder, production is minimized if reactions are at a steady state.

• Feedback control helps maintain homeostasis. The flyball governor is shown in this figure at http://www.uh.edu/engines/powersir.htm:
  

  For stability, feedback must be negative - the more the output of a process, the more negative feedback to the process, shutting it down.

• When homeostasis begins to fail, organisms move from regulation to conformity. (Eckert, Fig. 1-4)

3. Size and scaling

• We will discuss why proportions of animal bodies and their internal organs must change as we move from smaller to larger organisms.
• Why have larger organisms? What are evolutionary strategies of r and K-selection and how do these relate to an animal's body size? How is size related to temperature conformity or regulation?

All text and images, not attributed to others, including course examinations and sample questions, are Copyright, 2009, Thomas J. Herbert and may not be used for any commercial purpose without the express written permission of Thomas J. Herbert.