Choose the correct statement
Assertion [A]: Marine ecosystems have less trophic levels than terrestrial ecosystems.
Reason [R]: Most of phytoplankton is available for consumption and assimilation by primary consumers in aquatic ecosystems.
In marine ecosystems, phytoplankton carry out most of the photosynthesis that occurs. Phytoplankton are small organisms like diatoms with extremely simple structures. So most of their primary production or biomass is consumed by grazing organisms that feed on them. In contrast, a large fraction of the biomass that land plants produce, such as roots and trunks, are complex and cannot be consumed by herbivores for food, so proportionately less energy is fixed through primary production in terrestrial ecosystems. This is the reason why terrestrial ecosystems have smaller food chains or less trophic levels than marine ecosystems.