BIOL 322 Final Exam Questions and Answers

What are the criteria of hydrostatic skeletons? - Fluid maintained at constant volume - container for fluid must be deformable - container for fluid is wrapped in muscle and connective tissue Any deformable, incompressible material maintained at constant volume can act as a hydrostatic skeleton What is the mechanical advantage for cylindrical hyrdostats As a cylinder of constant volume changes shape there is a non-linear relationship between its diameter length How to extend tentacles or arms Contract any muscles that reduce cross-sectional diameter upon shortening (circular muscles, radial muscles, transverse muscles) How to shorten muscles or arms Contract any muscles that reduce length (longitudinal) Why can the tentacles extend farther than the arms because they are longer initially For an echinoderm tube foot Circumferential tensile stress = 2 X axial tensile stress For a sea anemone circumferential tensile stress = (internal pressure X radius of cylinder) / wall thickness What is the importance of collagenous connective tissues for internally pressurized cylinders - prevents ruptures - helps limit/control shape change How are these solved? A lattice work of crossed helical fibres (collagen) What is the shape of the curve for a stress strain plot of crossed lattice of fibres It is J shaped What is the role of collagenous connective tissue? 1) Allow modest increase in circumference 2) Limit extreme increase in circumference Sea Anemone Mesoglea "single material can serve a variety of skeletal functions requiring different material properties if those functions occur on different time scales"