The mass of all producers in the mountains was 500 tons. One kilogram of phytomass contains 800 kcal of energy.

The mass of all producers in the mountains was 500 tons. One kilogram of phytomass contains 800 kcal of energy. Determine what is the maximum number of 1st order predators that can feed in a given ecosystem if their average weight is 4 kg, and 100 g of their body contains 500 kcal of energy.

1) Let’s make a diagram of the food chain:
phytomass (producers) -> herbivorous animals (1st order consumables) -> 1st order predators (2nd order consumers).
2) Let’s calculate how much energy is stored at trophic level I:
1 kg contains 800 kcal 500 t (500,000 kg) – x kcal x = 4 * 10 ^ 8 kcal.
2) Let’s calculate how much energy will go from trophic level I to level II according to the 10% rule:
4 * 10 ^ 8 kcal – 100% x kcal – 10% x = 4 • 10 ^ 7 kcal.
3) According to the rule 10% 4 * 10 ^ 6 kcal of energy will be transferred from trophic level II to level III.
4) Let’s calculate how much energy is contained in the body of one predator of the 1st order:
100 g (0.1 kg) contains 500 kcal 4 kg – x kcal x = 20,000 kcal.
5) Let’s calculate how many predators can feed in a given community:
4,000,000 (4 x 10 ^ 6 kcal): 20,000 kcal = 200.
Answer: 200.