PNB 2250 Lecture Notes - Lecture 5: Torpor, Codevelopment

• School: UConn
• Department: Physiology and Neurobiology
• Course: PNB 2250
• Professor: Joseph Crivello

Document Summary

Understand evolutionary process in respiratory organ development. Life developed in the ocean: limited oxygen, other constraints, possible hypoxia. Drive toward terrestrial existence: danger of desiccation, gills poorly suited for terrestrial life. Timeline: 430 mya air-breathing fish appeared. Evidence supporting air-breathing fish evolution: likely the ability to gulp air came first, what is needed for air-breathing fish. Ability to control muscles to gulp air. Development of a sac (from the pharynx) where gas exchange can take place. Changes in the patterns of blood flow to the developing air sac. Further development of a 2-cycle or 4-cycle breather. Other considerations: lungs in fish change buoyancy (hard to swim too far from the surface, energy required to swim to surface to gulp air is significant. Breathing came first: fossil record suggests breathing arose twice, cydic process. Requires ability to dose nose and block air to digestive system: driven by changes in blood-gases.