Presentation on theme: "You, Chickens, and a Desert Island An energy pyramid problem."— Presentation transcript:
You, Chickens, and a Desert Island An energy pyramid problem
The original question: You’ve been stranded on a deserted island with no food except what washed ashore with you. You find a solar still for making fresh water, one cage containing five live chickens, and a large packing crate full of breakfast cereal. You do some quick calculations and realize there are enough calories in the cereal to keep you OR the chickens alive for 20 days. According to what we have learned about food chains and energy pyramids, which of the following plans will maximize the calories available to you, allowing you to survive the longest in hopes of rescue? There is only ONE correct answer. Yes, really. Feed all of the cereal to the chickens, then eat them. Feed all of the cereal to the chickens and eat their eggs. Kill the chickens and eat them, then eat the cereal. Share the cereal with the chickens. Eat their eggs, then eat the chickens when the cereal runs out. Set the chickens free to fly home, and eat the cereal.
Rationales for “share cereal, eat eggs, eat chickens” and “feed chickens, eat eggs” Sharing cereal feeds chickens, which lay eggs, which you can eat – “no energy loss” model of the food chain. Sharing cereal increases the amount of energy/nutrients that you get – “energy accumulation” model of the food chain. Eggs/chickens have “more calories” than cereal – perceptions about energy content of foods. Eggs/chicken meat have “more nutrition” than cereal – perceptions about nutrient value of foods. Chickens are “producers” – alternative perceptions about ecosystem production.
Rationales for “eat chickens, eat cereal.” Feeding cereal to the chickens means only 10% of the energy in the cereal is passed on to you – “energy loss” model of the food chain.
Do the math! Use the worksheet provided and calculate the number of calories that each of the five strategies would yield. When calculating number of calories from eggs: Chickens will use up about 90% of the calories they receive. About 10% is turned into chicken and egg. As a very generous estimate, figure that about half of the cereal calorie input will become egg calorie output, so multiply the calories put into the chickens by 0.05.
Now – which strategy will maximize your calories for the longest survival? A. Share cereal with chickens, eat eggs, then chickens. B. Eat chickens, eat cereal. C. Share cereal with chickens, eat the eggs. D. Let chickens go, eat cereal.