[问答题]
1.Draw and label a trophic pyramid of z3xrbkk ehy*(3m 9hh7n)*bw fenergy showing four levelq/:f p s,ozd;ns.
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.
