Which factor best explains why biomass decreases as trophic level increases in a food pyramid?
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A. Some energy is converted to heat B. Survival rate of organisms gradually decreases C. Availability of space decreases as feeding levels increase D. Toxic chemicals get more concentrated as they move up the food web
The answer to this is C. The availability of space decreases as feeding levels increase. The number of organisms available in the pyramid usually decrease for each level. There is also more food that are available at the lower trophic levels. If there would not be enough food in the lower trophic levels then the higher trophic levels will not get enough food as well. This can become a problem in the long run.
Remember that only the energy stored in the tissues is transferred from the organism that is consumed from the lower trophic level. If there is one species that would stop existing, there are other species in the food pyramid that will be gone after some time too. Species need certain species in order to survive.