For most terrestrial ecosystems, pyramids composed of species abundances, biomass, and energy are similar in that they have a broad base and a narrow top. The primary reason for this pattern is that
A) secondary consumers and top carnivores require less energy than producers.
B) at each step, energy is lost from the system because of the second law of thermodynamics.
C) as matter passes through ecosystems, some of it is lost to the environment.
D) biomagnification of toxic materials limits the secondary consumers and top carnivores.
E) top carnivores and secondary consumers have a more general diet than primary producers.

Question

Quizplus · Accepted Answer

The broad base of the pyramid represents the large amount of energy that is transferred from producers to primary consumers, whereas the narrow top represents the small amount of energy that is available to top carnivores. This reduction in energy transfer occurs because of the second law of thermodynamics, which states that energy cannot be converted without the loss of usable energy. Therefore, at each step in the food chain, energy is lost as heat, making it difficult for energy to accumulate at higher trophic levels.

For Most Terrestrial Ecosystems, Pyramids Composed of Species Abundances, Biomass