Do herbivores have more biomass than carnivores and why is not all the energy transferred to the herbivores converted into biomass?
Has to do with the second law of thermodynamics - entropy. There is never complete transfer of energy from one trophic level to another. There is waste in the form of energy used and heat produced and incomplete digestion etc, so that the often published rule is 10% per trophic level. Of course this depends on what is being transferred. Long chain omega 3 fatty acids are transferred at a more efficient rate.
Biomass decreases with each trophic level. There is always more biomass in lower trophic levels than in higher ones. Because biomass decreases with each trophic level, there are always more autotrophs than herbivores in a healthy food web. There are more herbivores than carnivores. In a typical ecological pyramid, the biomass of carnivores is less than the biomass of herbivores. This is because energy is lost at each trophic level as it is transferred from one organism to another. In general, only about 10% of the energy from one trophic level is passed on to the next level. Carnivores produce less waste, since they mainly eat meat. However, parts such as bones or teeth are difficult, or impossible, to digest. These parts are also lost as faeces if an animal eats more protein than it needs; the excess is broken down into amino acids. Energy is lost with each trophic level, so it takes more of the sun's energy to ultimately produce a pound of meat to feed a carnivore than it does to produce a pound of plants to feed an herbivore. 10% of energy is passed from one trophic level to the next. With less energy at higher trophic levels, there are usually fewer organisms as well. Organisms tend to be larger in size at higher trophic levels, but their smaller numbers result in less biomass. When an herbivore eats a plant, it does not get all the energy the plant received from the sun. This decrease is because the herbivore may not eat all parts of the plant, and it may not be able to digest what it does eat. These undigested plant parts are excreted as waste. The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert to the Sun and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels, it is no longer available to the previous level. Herbivores cannot digest all of the plant material they eat, since they do not have the enzymes, e.g. to digest cellulose. This means that large amounts of plant biomass cannot be broken down and absorbed into the body. Undigested material is passed out of the body as faeces. Energy is lost with each trophic level, so it takes more of the sun's energy to ultimately produce a pound of meat to feed a carnivore than it does to produce a pound of plants to feed an herbivore. 10% of energy is passed from one trophic level to the next.
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