BSCI 207 Fall 2015
Homework #5: Terrestrial locomotion
Please type your answers into this document and upload to ELMS by
11:59 P.M., Wedenesday, 2 December
You may work on this homework on your own or discuss it with others. If you work through
questions with others, be sure to turn in your own work, at the level at which you understand
it. Do not simply copy answers from or for someone else. Questions such as these will show
up on exams, so be sure to work to understand how to arrive at the answers.
(1) Big fish swim substantially faster than small fish and big birds fly faster than
small ones. The speeds of running mammals, however, vary a lot less with body
size, although big ones do go somewhat faster. Assume that the energetic cost of
transport (cost per distance) varies with (body mass)0.68 and that maximum
metabolic rate varies with (body mass)0.81.
a) Is the mass-specific cost for a large runner to move a given distance higher,
lower, or the same as the cost for a small runner to move that same distance?
b) Is mass-specific maximum metabolic rate for a large runner higher, lower, or
the same as that for a small runner? Explain.
c) How many times faster should a 500 kilogram bear be able to run than a 50
gram rodent? Show your work.
(2) Below is a diagram of an alligator skull. “Effort” indicates where the muscle
contracts to close the jaws.
a) Does the lever system represented by alligator jaws chomping down on a tasty
morsel represent a Class 1, Class 2, or Class 3 lever? Why?
Class 3 because it is arranged as: Fulcrum, Force, then load. The force is the
middle contributor, not the fulcrum (class 1) or the load (class 2).
b) Is the mechanical advantage (=force advantage) less than 1, 1, or greater
than 1? Explain what this means and how you determined the MA.
Because the force is close to the fulcrum, the mechanical advantage is less than
one. This means that the jaws will require more force put in that let out. This
gives the jaws a speed advantage and makes it so it can move a larger distance.
c) Is the velocity advantage less than 1, 1, or greater than 1? Explain what this
means and how you determined the velocity advantage
Velocity advantage is greater than 1. Velocity advantage is the reciprocal
(inverse) of mechanical advantage and it means the jaws can move more rapidly
d) What is the biting force of the alligator at points “A” and “B”? Show your
) = 409.1 N
B) Fload = 1500 N (
) = 500 N
A) Fload = 1500 N (