1. Mechanical advantage is a ratio of the length of the effort arm (effort, E, to fulcrum, F) to that of the resistance arm (fulcrum to resistance, R). That is, MA = L_E/L_R. In a second-class lever, the components are in the order FRE, so the effort arm is always longer than the resistance arm and MA is always greater than 1. In a third-class lever, the order of components is FER, so the effort arm is always shorter than the resistance arm and MA is always less than 1.

2. (a) MA = 17 cm/11 cm = 1.55. (b) Such a lever would exert more force than was applied to it; this is the meaning of any MA > 1. (c) A third-class lever could never have such measurements because, as explained in the previous answer, all third-class levers have an L_E < L_R.

3. Flexion of the hip, knee, and elbow as you sit; pronation of the forearm, extension of the elbow, and flexion of the shoulder as you reach out for the apple; flexion of the elbow and extension of the shoulder as you bring the apple toward your mouth; depression and protraction of the mandible as you open your mouth to take a bite; elevation of the mandible as you bite it; and retraction and cyclic elevation, depression, and lateral and medial excursions of the mandible as you chew it.

4. Tendon denotes a fibrous connection from a muscle to a bone, and thus aptly describes the superior portion of this strip, which extends from the quadriceps femoris muscle to the patella. Ligament denotes a fibrous connection from one bone to another, and thus describes the connection from patella to tibia.

5. You would not be able to find a saddle joint in these animals. Its absence makes opposition of the first digit impossible.

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