Why do things higher in the food chain transfer less energy than things lower in the food chain

It basically boils down to this…
“For each movement upward, the efficiency of energy utilization is only 10%. “
Think about this chain…

Human – Big Fish – Medium Fish – Small Fish – Algae
Human <- 100 <– 1000 <-10000 <– 100000

Given this rule of thumb, it would take one hundred thousand calories of algae just to get 100 calories of fish to the human!

For a more in-depth and technical expiation, see the links.