Are chicken embryos endotherms or ectotherms? A laboratory exercise integrating concepts in thermoregulation and metabolism

Abstract

This investigative laboratory exercise uses the different relations between ambient temperature and metabolic rate in endotherms and ectotherms as a core concept to answer the following question: What thermoregulatory mode is employed by chicken embryos? Emphasis is placed on the physiological concepts that can be taught with this exercise, including methods for measuring rates of oxygen consumption, the relation between oxygen consumption and metabolic rate, the influence of temperature on metabolic rate, and the differences between endotherms and ectotherms both in the overall magnitude of metabolic rate and in the shape of the relation between metabolic rate and ambient temperature. Included in this article are respirometer designs suitable for teachers working with a wide variety of budgets and available equipment, specific laboratory protocols for collecting data, sample data, thought questions with sample answers, and suggestions for classroom implementation as a 1-, 2- or 3-wk laboratory exercise that can be taught at a variety of undergraduate levels.

The strong-inference protocol: not just for grant proposals

“…In the Appendix, more specific content is described for the case of a student-designed experiment described in the companion article "Are chicken embryos endotherms or ectotherms?" (7). In this experiment, students investigated the thermoregulatory mode of chicken embryos by measuring respiration rates (V O 2 ) at different ambient temperatures and comparing their results with the signature relations between temperature and metabolism in endotherms and ectotherms.…”

“…Finally, students need to explain how what they will measure (V O 2 ) is related to metabolic rate, the physiological function that they are investigating in this experiment (see Ref. 7).…”

Teaching simple experimental design to undergraduates: do your students understand the basics?

“…Teaching simple experimental design to undergraduates: do your students understand the basics? Adv Physiol Educ 31: 82-92, 2007; doi: 10.1152/advan.00033.2006.-This article provides instructors with guidelines for teaching simple experimental design for the comparison of two treatment groups. Two designs with specific examples are discussed along with common misconceptions that undergraduate students typically bring to the experiment design process.…”

“…The specific procedures and theoretical basis of this experiment are described in greater detail in the companion article "Are chicken embryos endotherms or ectotherms?" (10). However, the general concepts, discussion plan, and thought questions are applicable to any experiment in which the effects of two treatment conditions are being compared.…”

“…Writing this short but important document helps students to process what they have discussed in class, prepares them for performing the experiment, and provides ideas and text for the final laboratory report. For a general discussion of the stronginference protocol and specific examples for the chicken embryo metabolism experiment, see the companion article (10).…”