BIOL 330 Lecture Notes - Lecture 10: Cool Air, Visual Cortex, Exhalation
24 Mar 2017
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Document Summary
Two modes of vertebrate life on land: synapsids vs. sauropsids. Sauropsids are reptiles and birds, and synapsids are mammals. Both are amniotes, although some amniotes live in water. These two groups are the major evolutionary split of amniotes. Amniotic egg: support, water movement, reproduction (locations, larger eggs produce larger offspring. Amniotes had evolved few derived characters associated with terrestrial life when this split occurred. Each lineage independently evolved parallel strategies, (but different characters) to live on land: locomotion, respiration, transporting oxygen, thermoregulation, conserving water, eliminating wastes (excretory system) Early tetrapods moved with lateral undulations of the trunk and axial muscles. The axial muscles bend the trunk laterally and compress the rib cage bilaterally to ventilate lungs. Not enough oxygen for running long distances. Synapsids: upright posture; limbs underneath trunk, loss of ventral ribs, development of a diaphragm (flattened when contracted, towards head when relaxed); contraction permits air inhalation (neg/ pressure in lungs) Fore/aft limb movement, so no (lateral) trunk bending.
