What is the key concept for this section? Define and distinguish between a food chain and a food web. Explain what happens to energy as it flows through food chains and food webs. What is a pyramid of...

What is the key concept for this section? Define and distinguish between a food chain and a food web. Explain what happens to energy as it flows through food chains and food webs. What is a pyramid of energy flow? Distinguish between gross primary productivity (GPP) and net primary productivity (NPP), and explain their importance. What are the two most productive land ecosystems and the two most productive aquatic ecosystems? What percentage of the world’s NPP do humans use?