[This is a play, and you are an actor in it. Agree with your partner about who will be Bing and who will be Bong. Then read the play, being sure to follow any stage directions that appear in brackets.]

Bing has arranged to meet Bong at the local health spa to get a little exercise. Bing has been waiting for about 10 minutes when Bong arrives.

Bing Well, Bong, you certainly do have a lot of energy today. Imagine running to a health spa so that you can exercise!

Bong [Panting somewhat] Sorry I'm late, Bing. That's why I was running, not because I have any extra energy. I just hated to keep you waiting. I went to the grocery store this afternoon, and I managed to get into that lane that every store seems to have that is slower than all of the others.

Bing Ah, yes. I've been in that lane too, Bong. Don't worry a thing about it. One reason I come to the spa is to relax after a hard day of work, and I've had good opportunity to relax while waiting for you. So you were at the grocery store, were you. Are you still on that vegetarian kick?

Bong It's not a "kick", Bing. It's a responsible life style for the 1990's. I save a great deal of energy by eating plants instead of meat.

Bing Not me! When I eat lots of vegetables I find that I have to chew a great deal more than if I eat a hamburger.

Bong That's not what I mean by "saving energy", Bing. I had in mind an important ecological insight which I gained by taking a biology course at Hope College. It has to do with the way energy moves through ecosystems. As I learned this important truth, I suddenly realized, "Hey! I'm part of an ecosystem too", so I am now trying to bring my life into accord with scientific principles.

Bing Bong, you never cease to amaze me. Each time we talk, you seem to have adopted some new weirdness. So you've become part of an ecosystem, have you. What is an ecosystem anyway, some aspect of the information super highway?

Bong [With an exasperated sigh] You don't "become" part of an ecosystem, Bing. You just are a part. An ecosystem is any complex of plants, animals and microorganisms that interact with each other and the physical environment. A jar of pond water can be an ecosystem, and so can all the living things on the earth.

Bing [With a glassy eyed stare, frequently seen in people who are bored] Ah, I see, and we interact with the cows and the lettuce and each other as well as the air and the sun and the rocks. But, so what, Bong. How is that definition related to the claim that you are saving energy by being a vegetarian?

Bong Every ecosystem runs on the energy that comes from the sun. Plants trap that energy and convert it into chemical energy in sugars -- that's what photosynthesis is. Some of that energy is used by the plant, but some is passed on to things that eat plants. They use part of the energy and pass some on to things that eat things that eat plants. And so on. At every step, a very significant amount of the energy is lost as heat. We living things are not 100% efficient in our use of energy. In fact, only about 10% of the energy trapped by plants is passed on to plant eating animals, and only about 10% of the energy in plant eating animals is passed on to meat eating animals. The rest is lost as heat as the organisms carry on their day to day activities.

Bing [Showing interest at last] 10%!! Are you saying that 90% of the energy taken in by each level in these food chains is unavailable to the next level, lost as heat?

Bong I believe I did say that, Bing. Ecologists have actually determined this by very laborious observations on ecosystems such as the Silver Springs in Florida and a number of other cases.

Bing And what happens to all that energy that is lost?

Bong It's just lost -- it contributes to the random movement of the molecules in the universe, which is what heat is, I guess. In effect, energy runs through an ecosystem in one direction, from the entrance of sunlight on the surface of leaves to the last bit of skin on a dead lion being disintegrated by decomposing fungi.

Bing [Standing up in excitement at his discovery] Goodness gracious, Bong. Even the prehistoric plants are part of our ecosystem. They trapped sun's energy millions of years ago, and only now is much of that energy being consumed by us as we burn coal and petroleum. Think of it, fossil energy, and we're only getting about 10% of that energy too, I suppose.

Bong [Calming Bing with a pat on the hand] Less, I would imagine, Bing. Automobile engines and electric power plants are not nearly so efficient as living cells. More yet is being lost as heat. But now, before we get to the bottom of this page, do you see why I'm saving energy as a vegetarian?

Bing Why, yes. It only takes one-tenth the vegetables to support your energy needs as it would if those vegetables were first fed to cows and hogs and then the meat was used for your energy needs. If we all only ate plants, we could support 10 times as many people in the world than if we ate meat.

Bong Well...yes...or the number we have 10 times as well.

Bing Oh, dear. We've become so engrossed in our discussion about this interesting topic that the health spa is closing before we could go in to exercise.

Bong That's ok, Bing. I'm late for my next appointment anyway, so I'll just run along. You should try scheduling more things into your day. You'd get more exercise.

Donald Cronkite, 1994