Why must sustainable food webs be structured this way?

Question

Sustainable food webs often look like triangles when considering the relative amount of organisms in each part of the food web. Specifically, sustainable food webs have relatively large numbers of autotrophs, followed by fewer herbivores. These food webs also have even fewer numbers of carnivores than they do herbivores. Given what you know about the Laws of Thermodynamics, explain why sustainable food webs must be structured this way. You need to specifically reference the Law of Thermodynamics you are using to support your argument and explain why what that Law tells us supports the sustainable food web structure described above. 

Answer 1

The answer to your question has to do with energy transfer from one trophic level to the next.

Primary producers (autotrophs) make up the base of the pyramid.

As organisms in each of the trophic layers consume organisms in the lower trophic level, they uptake energy from the level they consume.

Unfortunately, not all of the energy that one tropic level produces is passed up to the next level tropic level.

The level of energy passed from one trophic level up to the next higher level averages only about 10%.

Because of the relatively inefficient transfer upwards, from primary producer to consumer, there must be more primary producers in order to sustainably feed fewer consumers.

The first and second laws of thermodynamics are at play here.