[问答题]
1.Draw and label a trophxo*,*t-;v ln(ujx9j sqg0in3hm )z h dic pyramid of energy showin v 3c()5mxlqnag four levels.
2.Explain how the presence of a food web in an ecosystem makes it more stable than the presence of a single food chain.
3.The production and transfer efficiency of energy varies between ecosystems.
Describe how energy flows in and out of terrestrial ecosystems.
