You are a patent agent, and an inventor comes to you claiming that he has invented a self-powered engine that requires no fuel to run. Will you agree to patent this invention? Why or why not?
I would not agree to patent such a device. I have studied perpetual motion for some time. I used to be very fascinated by the idea. After I graduated high school I started reading a lot. I read a book called Five Equations that Changed the World. It included information about Faraday, Clausius, Newton, Bernoulli, and Einstein. Anyways after reading about Clausius and the laws of thermodynamics, I realized that it was impossible. It is a fairy tale because any device that does work has to get its energy from somewhere. In the case of this man, I would politely explain that he might have found a new form of fuel not yet completely understood, but that the engine had to get its energy from somewhere to do the work. I would explain that we could patent the device as a new engine that used a newly discovered form of energy but that I could not patent the device as not requiring fuel to run. If he had more concerns I would kindly shed light on the fact that energy takes many different forms; namely, kinetic and potential. Then I would explain that even though energy can change between the different types the net amount never changes. Therefore an engine that does not use any fuel is impossible; because if the net amount of energy never changes, then the energy has to come from somewhere.
When a hawk eats a fish, does the hawk acquire all of the energy contained in the body of the fish? Why or why not?
To be honest I am not sure what the second law of thermodynamics has to do with either of these questions. I will give it a shot though. The answer is no. When energy changes form entropy always increases. When the hawk eats the fish energy is changing from whatever form it was in the fish to something useful for the hawk. All of the leftovers from this process, called metabolism, are expelled as waste. If the hawk could absorb all of the chemical energy from the fish then there would be no waste. However, hawks cannot and whatever energy the hawk cannot use is dispelled.
What implications do you think this answer would have for the relative abundance (by weight) of predators and their prey?
Not so sure about this one either. There are more prey than there are predators. The prey weight less than the predators. Since only a part of the energy in the prey can be used when consumed the predators must eat much prey to escape the inevitable move towards entropy.
Pruitt, N. L., & Underwood, L. S. (2006). Bioinquiry: Making connections in biology (3rd ed.). Hoboken, NJ: John Wiley & Sons, Inc.