[问答题]
1.Draw and label a tj,p)e aw. zdv)j2m.ev+jrw*b+ x upe-+avx.xst -ng2rophic pyramid of energy showing 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.
