Question

In the following food chain, plants provide ${\rm{500}}\,{\rm{J}}$ of energy to rats. How much energy will be available to hawks from snakes?
Plants → Rats → Snakes → Hawks

Answer 1

There are limits on the number of trophic in the food chain as the energy transfer complies with the ${\rm{10\% }}$ rule. Just ${\rm{10\% }}$ of the energy from the lower trophic level is transferred to each trophic level.

Complete answer:
The flow of energy, also known as the calorific flow, refers to the flow of energy via a food supply chain. Ecologists aim to measure the relative importance of various organisms and feeding relationships within an ecosystem. The energy passes from trophic to trophic levels and every time about ${\rm{90\% }}$ of the energy goes lost, some are lost as heat (effect of breathing) in the environment and others are lost as food that is incompletely digested. Primary users get about ${\rm{10\% }}$ of autotrophic energy, while secondary users get about ${\rm{1\% }}$ and tertiary users get about${\rm{0}}{\rm{.1\% }}$.
This means that a food chain's top consumers obtain the least energy, since much of the control of the food chain between trophic levels has been lost.
We know that the energy passes from one trophic level to other is only ${\rm{10\% }}$
In the given food chain, the energy provided by the plants to rats is ${\rm{ = }}\,{\rm{500}}\,{\rm{J}}$
Therefore, the energy provided to snakes by rats is ${\rm{ = }}\,{\rm{500}}\,{\rm{J}}\,{\rm{ \times }}\,{\rm{10\% }}\,{\rm{ = }}\,{\rm{500}}\,{\rm{J}}\,{\rm{ \times }}\dfrac{{{\rm{10}}}}{{{\rm{100}}}}{\rm{ = }}\,{\rm{50}}\,{\rm{J}}$
The energy available to Hawks from Snakes is ${\rm{ = }}\,{\rm{50}}\,{\rm{J}}\,{\rm{ \times }}\,{\rm{10\% }}\,{\rm{ = }}\,{\rm{50}}\,{\rm{J}}\,{\rm{ \times }}\dfrac{{{\rm{10}}}}{{{\rm{100}}}}{\rm{ = }}\,{\rm{5}}\,{\rm{J}}$

So, the hawks get the ${\rm{5}}\,{\rm{J}}$ energy from snakes.

Note: The energy passes from tropic to trophic levels and every time about ${\rm{90\% }}$ of the energy goes lost, some are lost as heat (effect of breathing) in the environment and others are lost as food that is incompletely digested. Primary users get about ${\rm{10\% }}$ of autotrophic energy, while secondary users get about ${\rm{1\% }}$ and tertiary users get about${\rm{0}}{\rm{.1\% }}$.