Background
A trophic level, or feeding level, is made up of all the organisms whose energy source is the same number of consumption steps from the sun in a given ecosystem. The trophic level of plants or producers is 1, while that of herbivores is 2 and that of animals that eat herbivores 3. Higher trophic levels can exist for animals even higher on the food chain. In this exercise, you will compute numerical values for human energy needs based on diets at different trophic levels.
In this case study the owner of a farm raises soybeans and chickens. Grasshoppers feed on the farmers soybeans, and are in turn eaten by the chickens. Humans can, though rarely do, eat grasshoppers for sustenance. Humans can also eat soybeans. For the purpose of this exercise, make the following assumptions:
- A human requires 1 chicken/day
- There are 365 days/year
- 1 chicken eats 25 grasshoppers/day
- 1 grasshopper requires about 30 g of soybeans/year
- 1,000 grasshoppers have a mass of 1 kg
- 1 human requires about 600 grasshoppers/day
- Dry soybeans have about 3.3 cal/g
- There are 1,000g/kg
- A typical human requires 3,000 cal/day
- How many grasshoppers does a chicken need to survive for a year?
2. How many chickens would a human need to survive for one year?
3. How many grasshoppers are needed for a year’s supply of chickens for one human?
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