Question

Which of the following is true with respect to phytoplankton?

• A. Phytoplankton grow more rapidly than land plants
• B. Phytoplankton have simple structures with more consumable matter than land plants
• C. Phytoplankton have higher primary productivity than land plants
• D. All of these
• E. None of these

Answer 1

The correct option is D All of these

As most of the energy is lost during its successive transfer in each trophic level of the food chain, most terrestrial ecosystems have no more than five trophic levels, and marine ecosystems generally have no more than seven. In marine ecosystems, microscopic phytoplankton carry out most of the photosynthesis that occurs, while plants do most of this work on land. Phytoplankton are small organisms with extremely simple structures, so most of their primary production is consumed and used for energy by grazing organisms that feed on them. In contrast, a large fraction of the biomass that land plants produce, such as roots, trunks cannot be used by herbivores for food, so proportionately less of the energy fixed through primary production travels up the food chain. Phytoplankton are extremely small but grow very rapidly, so they support large populations of herbivores. In contrast, land plants may take years to reach maturity, so their growth rate is lower.