Vertebrate Zoology
Mammalia Lab II Locomotion
Using the figures, specimens and materials on the lab tables, identify
the structures and answer the following questions.
1. After reading the information on page 2, Use the meter
stick/fulcrum models of the human and horse leg to
demonstrate the advantage of having a proportionally short
femur. Apply an input force (movement) of 5 cm or some other
distance on the body side of the fulcrum. What is the resulting
output for each model? How does this relate to running speed?
2. Compare the three examples of rear limbs. Does bigger always
mean faster?
3. What conclusions can you draw from the leg bones provided?
4. What is the adaptive significance of increased speed for some
ungulates?
5. What assumptions can be made from the two different skeletons
about feeding, lifestyle, habitat, etc?
6. List some advantages and disadvantages to ungulagrady,
digitigady and plantigrady.
7. List some of the adaptations and their purposes for the following
types of locomotion:
a. Subterranean
b. Brachiating
c. Saltatorial
d. Gliding
e. Flight
f. Aquatic
g. Marine
h. Amphibious
i. Cursorial and ambulatory (from other stations).
8. What are some of the differences of flight in birds and in
mammals?
9. Using the horse evolution poster at the back of the room, what
conclusions can you make about locomotion and changes in
habitat of the equines represented?
Different Foot Types. From a comparative viewpoint, the
design of a vertebrate's foot is commensurate with its
lifestyle. The hind limb bones of a deer [left], dog
[middle], and badger [right] are shown in the drawing on
the right. These designs are called unguligrade ["hoofwalking"], digitigrade ["toe-walking"], and plantigrade
["sole-walking"], respectively. The badger is mainly a
walker and seldom runs, while the deer is a highlyadapted runner. The dog is in-between. Humans are also
plantigrade walkers, wherein the heel hits the ground first.
The diagram clearly shows that the 2 upper leg segments
are least modified, while the foot and toe area is most
modified. Note the relative position of the "heel" in each case. The highly-elongated
"foot" of the deer greatly increases its stride and speed. Although the proportions vary, on
an overall basis regarding number of joints and segments, however, the leg designs are all
similar.
Power and Speed. The figure below shows how a horse's legs bend at the "knees” while
galloping. Notice how closely built the knee of the back leg is to the torso, compared to
the ballerina's.
Clearly, the long lower leg sections, the leverage afforded by the powerful tendons, the
low degree of weight in the legs, and the huge muscles located in the upper legs and torso
all contribute to the speed and power of the horse. Because the upper leg sections are
relatively short, the major muscle groups (and weight) are all located close in to the body,
improving the angular acceleration of the legs for speed, while the elongation of the
lower leg segments greatly increases the stride.