Notes for the week of 10-15
Notes for the week of 10-15 BIOL 241
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This 3 page Class Notes was uploaded by Wilson on Thursday October 15, 2015. The Class Notes belongs to BIOL 241 at Indiana University of Pennsylvania taught by Dr. Duchamp in Fall 2015. Since its upload, it has received 31 views. For similar materials see Comparative Vertebrate Anatomy in Biology at Indiana University of Pennsylvania.
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Date Created: 10/15/15
L11 Adaptations for Movement Cursorial Locomotion 1 What is the advantage of posture change during mammalian evolution a Faster terrestrial movement this change in posture begins in reptiles b The orientation of the humerus changes as well as where the femur meets the pelvic girdle horizontal c Humerus shifts underneath so that the lower limbs are in line with gravity d Early tetrapods i Robust pectoral girdle ii Force is directed medially to resist gravity e Cursorial vertebrates i Rounded head of humerus in line with rest of bone ii Limbs are directly below scapula ii Clavicular bones reduced v Scapula become weight bearing f Synapsids posture change right before mammals i Go from primitive pelvic girdle to a more advanced one ii Head of femur will now fit tight with acetabulum deep pelvic iii Limbs move directly beneath the body g Mammalian posture resists gravity i Also helps with standing and stability ii If bones are aligned it takes less musculature to hold everything up and resist gravity h Reduction of adductor muscles i The muscles that bring limbs together ii Much more enlarged in primitive reptiles and are reduced in later models ii Allowed reduction in size of bones where adductors originate v lschium and pubis 1 These are made more efficient and lighter 2 Improved Efficiency of Limb Movement a Early tetrapods i Limbs move in a swimming motion ii Moves through multiple planes in a complex pattern iii This movement can be considered inefficient b Therapsids aves and mammals i Limbs move in a single plane ii Back and forth movement that is simplified straight line movement 3 What is the advantage of an increased length of limbs a Plantigrade full foot sits on the ground digits to calcanium humans Digigrade weight bearing part is on the phalanges cats Unguligrade distal phalanges tips of toe bear weight Metatarsal and metacarpals lengthened relative to femur and humerus Longer limb with same mass of bone same muscle output longer stride More distance is covered per movement The trend is to optimize speed to avoid being eaten as well as catch prey anhrbslosr h Digigrades are predators because of the grip support of their hands 4 What other adaptations do we see for cursorial locomotion a Reduction of digits and fusion of bones joint stabilization b Reduced weight at distal end of limb c Birds form tibiotarsus and tarsometatarsus d Typical bones fused in mammals i Metatarsalsmetacarpals and more distal bones ii Cannon bone fusion of metatarsals into a single bone in horses 5 What improvements occurred with anklefoot bones of mammals a Lengthening of metatarsals And the beginning of overlap between the talus and the calcaneal bone Callus astragalus Calcaneal is a heel bone callus is what your tibia rests on Instead of being separate and side by side they begin to overlap and become a more efficient joint 6 What are the advantages of the tibial tarsal joint a Tight fit of the astragalus between medial and lateral malleolus i Allows primarily a single plane of movement hinge joint ii Movement is directed forward during plantarflexion of the ankle iii Adds stability to an area with little muscle formation 7 How are muslces adapted for cusorial locomotion a Typical tetrapods i Muscles more uniformly distributed along the length of the legs ii In horses muscle is packed near the trunk and there is very little in the legs b Cursorial vertebrates i Muscle mass is proximal to the trunk ii Lightens weight distally iii Allows for quicker movements iv How do the muscles near the trunk move the bottom of the leg through tendons in a horse there are very long tendons 8 How is the pectoral girdle of tetrapods attached to the axial skeleton a No direct bone articulations b Muscular sling i Attach pectoral girld bones to thoracic vertebra and rib cage 1 Trapezius vertebrae to back 2 Rhomboideus 3 Serratus ventralis 4 Pectoralis humerus to sternum ii These connect pectoral girdle and forelimbs to axial skeleton 9 How are axial muscles different for mammals a Hypaxial muscles i Form continuous sheet ii Flex the vertebral column b Epiaxial muslces DPPPquot i Become more differentiated ii Extend the vertebral column iii Results in dorsalventral flexion fish have lateral flexion which is side to side movement 10 Why are there differences in the axial skeleton of digitigrade and unguligrade mammals i Digitigrade lumbar vertebrae Narrow neural spines Reduced transverse processes Relatively flat postzygapophyses Results in increased dorsal ventral flexion Increases stridelength ii Unuligradelumbarvertebrae 1 2 3 9quot Made to be sturdy Wide neural spines Tightly locking zygapophyses overlaps that keep the animal from sagging Results in limited dorsalventral flexion Increase stridelength is through lengthening of limbs Lumbar region supports large fermentation chamber for robust digestive tracts