What is the difference between primary productivity and secondary productivity in ecosystems?

• A. Primary productivity is energy captured by producers; secondary productivity is energy stored in consumer biomass from food eaten.
• B. Primary productivity is energy stored in consumers.
• C. Primary productivity is energy lost as heat.
• D. Primary productivity only occurs in oceans.

Answer: (A)

Understanding how energy moves through ecosystems is the key idea. Primary productivity is the energy captured by producers (autotrophs) through photosynthesis or chemosynthesis, and it’s stored as new producer biomass each unit of time. Secondary productivity is the energy that becomes biomass in consumers—the energy from the food eaten is converted into new consumer tissue and growth.

That makes the correct answer the best match: primary productivity is energy captured by producers, while secondary productivity is energy stored in consumer biomass from food eaten. Keep in mind that much of the energy taken in is used for metabolism and lost as heat, so only a portion becomes new biomass in consumers. Also, primary productivity occurs in any ecosystem with autotrophs (not just oceans), and secondary productivity depends on how efficiently consumers convert ingested food into biomass.