In a food chain 200 kg of wheat is fed on by 18 kg of mice which in turn are eaten by 1kg of hawk. What is the percentage energy transferred from the first trophic level to the third?

0.1% of energy

Explanation:

Energy flow: From the whole quantity of energy that reaches the earth's surface, autotroph organisms or producers absorb only 0.1 or 1%.

From the input of solar energy begins a unidirectional energy flow through all the organisms in the ecosystem, from autotrophs to heterotrophs, until it is dissipated in the environment.  

At each trophic level occurs an energy transfer to the next, with only 10% being usable in each of them. This assessment is called "The 10% rule". As a general rule, only about 10% of the energy stored as biomass at one trophic level, per unit time, ends up as biomass at the next trophic level, in the same unit of time.

If wheat transferred 10% of the energy to mice, and of that 10% mice transferred 10% of the energy to hawk, then the percentage of energy transferred from the first trophic level to the third equals 0.1%.

10% (1st TL-2nd TL) / 10% (2nd TL - 3rd TL) = 0.1% (1stTL - 3rd TL)

TL = Trophic level          

a. the production of carbon dioxide through the process of photosynthesis