Have you ever wondered why we can't seem to feed the world's hungry? It's a very complex issue, but it might surprise you to learn that it's not because we can't produce enough food-current agricultural capacity exists to feed as many as 10 billion people. The Earth's population is "only" about 6 billion (although it is predicted that by the early 21st century there will be over 10 billion). The big question really is: "If we want to feed everyone, what would we all have to eat?".

The answer has to do with the food chain. As you probably know, the organisms at the base of the food chain are photosynthetic-plants on land and phytoplankton (algae) in the oceans. These organisms are called the producers. The organisms that eat the producers are herbivores (vegetarians). They are called the primary consumers. The organisms that eat the primary consumers are meat eaters (carnivores) and are called the secondary consumers. This continues on, all the way up to the top of the food chain, and us. The problem is that about 50% of the energy in food is lost at each "trophic level" when an organism is eaten, so it is less efficient to be a higher order consumer than a primary consumer or producer. Because of this inefficiency, there is only enough food for a few top level consumers, but there is lots of food for herbivores lower down on the food chain, so there is room for fewer consumers than producers.

Example: One acre of a grain crop could be used to feed cattle, and then the cattle could be used to feed people. However, you could feed twice as many people if you fed them the grain directly, because 50% of the energy is lost to the cattle. Another way of looking at it is that it would only take a half acre of land to feed the people grain, but a whole acre if you feed the grain to the cattle and the cattle to the people.

1. Given: 10 billion people can be fed a basic vegetarian diet that is nutritionally complete. How many people could we feed at the American standard-a tertiary level of consumption (3rd order consumers?). 50% of the energy is lost by each higher level.

2. If there are 250 million people in the United States most of them eating at the Tertiary (3rd) level of consumption, how many people could we feed at the Primary level?

3. Some animals like sharks are 5th order consumers! Sharks eat tuna that eat mackerel that eat herring that eat copepods that eat diatoms. If we were to make the reasonable assumption that each of these animals eats 2 of its prey each day, how many organisms died to feed the shark in one day?