Question

dry weight (kg m - 2)
trophic levels
tertiary consumers
secondary consumers
primary consumers
producers
pyramid of biomass for grassland ecosystem
a biomass pyramid for a typical grassland ecosystem is shown here. what explains the changes in mass seen in the pyramid from the producer level to the next level?
a the solar energy available to each trophic level in the pyramid decreases, therefore the biomass of the organisms in each level continues to decrease.
b the recycling of nutrients decreases at each level of the ecological pyramid, decreasing the availability of matter and nutrients to each successive level in the pyramid.
c the decomposers digest the majority of the biomass of the primary producers, leaving fewer components to be consumed by the herbivores. this limits the growth of the herbivores to always be less than that of the primary producers.
d the primary producer level has more biomass than the primary consumers. primary consumers cannot consume all parts of the grasses, such as the roots and dead leaf litter. therefore, the biomass of the primary consumers will always be less than the biomass of the primary producers.

Explanation:

The biomass pyramid shows a decrease from producers to higher trophic levels. Option A incorrectly links biomass decrease to solar energy availability (solar energy is only captured by producers). Option B is wrong because nutrient recycling does not decrease at each level—nutrients are recycled back to producers. Option C is incorrect as decomposers break down dead matter, but this is not the main reason for the immediate decrease from producers to primary consumers. Option D correctly explains that primary consumers (herbivores) cannot consume all parts of producers (e.g., grass roots, dead litter), so their biomass is less than producers.

Answer:

D. The primary producer level has more biomass than the primary consumers. Primary consumers cannot consume all parts of the grasses, such as the roots and dead leaf litter. Therefore, the biomass of the primary consumers will always be less than the biomass of the primary producers.