Lecture 19.docx

Lecture 19: Evolving Behavior What Evolves? 1. Over Wing Scratching is an atavism (traits or characters of ancestral features) Phylogenetic hypothesis Under wing – ancestral bird pattern Over wing – reversion to ancestral quadruped pattern (atavism) Earlier stages of the organism’s past evolution pr...

Lecture 19: Evolving Behavior What Evolves? 1. Over Wing Scratching is an atavism (traits or characters of ancestral features) Phylogenetic hypothesis Under wing – ancestral bird pattern Over wing – reversion to ancestral quadruped pattern (atavism) Earlier stages of the organism’s past evolution precedes later additions Lorenz Atavism hypothesis is an inadequate explanation 2. A By-Product of Body Morphology or Context Necessity is critical Neither context nor morphology can explain scratching (over/under) behavior 3. Birds Inherited Two Behavior Patterns – A Dorsal Route and a Ventral Route Birds inherited both a dorsal and a ventral trajectory towards the head. Supportive of the Phylogenetic Hypothesis Under wing at base, the sporadic appearance of over wing Over wing occurs early in the branching pattern Over wing emerges in species of MANY different Families The two forms of scratching are two distinct behavior patterns and can evolve independently Problems of Development? No problems as pattern change can be Bidirectional Axial vs Limb Locomotor Vertebrate Axial Locomotion Segmental Central Pattern Generator (CPG) Left/Right sides being mutually inhibited Limbless animals CPG produces sinusoidal movements of body axis Alternating flexing of the left and right sides of the body Same for long bodied vertebrates Frog Transition from Axial to Limb Locomotion 1. Tadpoles = Axial, L/R side alternating 2. Early metamorphis = Axial 3. Late metamorphis = Rapid tail movements & slower symmetrical kicking movements 4. Adult = Tail been absorbed, legs propel body Even if gesture is different, closely related species can share a particular behavior system in their play Evolutionary hand replaces foot – but not for Biomechanical Reasons The hand gradually takes over from the foot Two Phases: Teeth are template for the foot Foot is template for the hand *The Importance of Inhibition