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Lecture 3

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ZOO 2090
Fred Laberge

Lecture 3 ZOO*2090 September 16, 2013 Overview of vertebrates cont’d Amniotes - Radiation/Diversification o relatively rapid expansion of a clade o adaptive radiation implies a particular adaptation driving the radiation o one should be careful not to mix concepts of pattern (increased diversity) and process Biological Design - understand size and shape of animals matter - describe interplay between muscles and skeletal system used to generate movement - external forces that effect vertebrates Size - square-cube Law: if you double the size of an object, you increase the surface area four times and you increase the volume it holds by 8 times - Surface Area o large size means relatively small surface area, leaving less space for exchange with environment (heat, gas, etc.) o “Comparative anatomy is the story of the struggle to increase surface area in proportion to volume” o scaling  student of size and its consequences - Metabolism o metabolism scales with size o heat loss proportional to surface area, but heat production proportional to volume - Supporting System o mass is proportional to volume o limb strength is proportional to cross-sectional area Shape - Allometry o allometry describes the changes in shape that accompany changes in size o all parts of the body are not growing at the same rate o allometric relationships can also apply to a phylogenetic trend within a group of organisms - Isometry o isometry is where there is proportional growth/change between all structures Force - biomechanics attempt to clarify biological design - basic physical concepts are length (distance), time (flow of events) and mass (inertia) Lecture 3 ZOO*2090 September 16, 2013 - Vector o vectors are measurements that have magnitude and direction o some muscles are built upon this principle o the change in an object’s motion is proportional to the force acting on it - Lever o muscles generate forces and skeleton applies these forces o this can be represented by torques and levers o forces acting at a distance from fulcrum produces torque o force on input lever arm moves output lever arm o either force or speed can be optimized because a long lever arm favours speed whereas a short lever arm favours force  example: biological designs in mammal forelimbs  diggers - strength  runners – velocity - Force and stability o sprawled limbs  lizards  very stable  massive adductor muscles needed  locomotion costly o pendulous limbs  dinosaurs, mammals  not stable, but much less force needed  rapid and efficient terrestrial  locomotion possible Environment - Land o on land the main force we deal with (weight) results from gravity - Fluid o the main force acting against animals in fluids is not gravity but
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