- Gharials and alligators (Figure 1) belong to the crocodilian family, they share similar body plans, hunt in the water, and both rely on stealth and explosive speed to ambush their prey. Despite all their similarities, the shape of their skulls and jaws are different. These differences reflect their different diets: while gharials almost exclusively eat fish, alligators eat a variety of prey which ranges from fish, turtles, to small deer. Gharials snap at fish, alligators use the power of their jaws to grab prey and drag it under the water.
Figure-1 Comparison of Gharial on the left and Alligator on the right
- How can we use our knowledge of levers to help explain why the jaws of an alligator and the jaws of a gharial?
- As we can see from Figures 2 and 3 the jaws of the gharial and the alligator have similar architecture despite their different geometries.
- What type of lever system best represents and alligator jaw? Type 1, 2 or 3?
- Online resource - Review of Levers
Figure-2 Alligator jaw represented as a lever
Figure-3 Gharial jaw represented as a lever
- How can we use our knowledge of levers to help explain why the jaws of an alligator and the jaws of a gharial?
- As we can see from Figures 2 and 3 the jaws of the gharial and the alligator have similar architecture despite their different geometries.
- What type of lever system best represents and alligator jaw? Type 1, 2 or 3?
- Online resource - Review of Levers
- Calculate bitting force
- Using the information provided in Figure 4 calculate the bitting force for an gharial at points A and B
- Now calculate the bitting force for the alligator (Figure 5) at points A and B
- Which one has the highest bitting force, the alligator or the gharial?
- Bitting motion
- Levers can be used not only to increase force as shows above, but also to increase the range of motion. In the case of the jaws of the alligator and gharial, the lever system formed by the jaw and skull allow for the small motion of the jaw muscle to be translated into a relatively large motion at the tip of the jaw.
- Calculate the motion of the the gharial jaw (Figure 4) at points A and B assuming that there is a motion of 0.01 m at the effort.
- Calculate the motion of the the alligator jaw (Figure 5) at points A and B assuming that there is a motion of 0.01 m at the effort.
- Which one has the greatest range of motion, the alligator or the gharial?
- Assuming that the alligator and gharial can contract their jaw muscles at the same speed, which one is likely to be better adapted to catch fast moving prey? Which one is better adapter to capturing powerful and heavy prey?
- Brainstorm: Does it seem reasonable for gharials and alligators to have muscles capable of exerting the same level of force?
Figure-4 The jaw of a Gharial modeled as a lever
Figure-5 The jaw of an Alligator modeled as a lever