[问答题]
1.Draw and label a trophj5a2i9 8f kwz+kj8: gq jtj+uhic pyramid of energy showin8h.cxjys.rb7kfe4 8h g 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.
