How does a herbivore benefit from the sun's energy?

Answer 1

Overall, an extremely low amount. Even plants do not have high primary productivity (amount of light energy converted to chemical energy) compared to the sun's total energy output. The sun's light is absorbed or reflected; a substantial amount is reflected. Even then, plants can only utilize certain wavelengths of light - while others cannot be used. All in all, only about 1% of all sunlight that comes into the Earths atmosphere is actually used in photosynthesis. But of that energy that is assimilated by plants, again, not all of it is going to be passed on to the next level -- primary consumers.

The green world hypothesis states that there will always be more "green" or plants than the herbivores or primary consumers can eat. These herbivores are held in check by a variety of reasons, but ultimately much of the biomass of the primary producers is never passed along. This contributes to a large chunk of the energy that is not passed to primary consumers. On average, only 10% of available energy within any trophic level is passed along to the next level (depending on the ecosystem and trophic structure). So we could say that of the 1% energy that the plants use in primary productivity, 10% of that is present in primary consumers. Or 0.1% of the sun's total energy intercepted by Earth goes to the world's primary consumers.

This percent is further reduced when you only account for small herbivores. There are many different types of primary consumers who might actually be present in a different trophic level, which is often the case with decomposers. The number of small herbivores varies within ecosystems, though in most, they do not comprise a large population.

Answer 2

The sun's energy provides for plants so that they can perform photosynthesis. This helps the plant to grow and thus indirectly benefits the herbivore that eats the plant.