Energy Flow & Ecological Pyramids - Free MCQ Practice Test with solutions,

Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials. Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world.

B. Zooplankton are the primary consumers.

Primary consumers are organisms that feed directly on producers and obtain energy by consuming them.

In aquatic grazing chains, phytoplankton function as producers and are eaten by zooplankton, placing zooplankton at the primary-consumer level.

Phytoplankton are producers; carnivores feed on other animals and are secondary or higher-level consumers; and decomposers break down dead organic matter rather than acting as primary consumers.

Therefore, option B is correct.