Science Buddies: "Ask an Expert"

Ok my teacher says make 6 sentences for each question. There are two questions.

1. Explain how oxygen cycles through the ecosystem in which you live.
2. Consider how might ecosystems be affected if levels of atmospheric carbon dioxide continue to rise.

I read the chapter on it in the grade 7 Glencoe science thext book and i cant find it and i really need help. My teacher hasn't even taught us this. Thank you for whoever helps me

Hello,
The Science Buddies forum are for students in grades K-12 who are working on science projects. The experts in this forum are here to help with science projects, not homework. There are more appropriate forum elsewhere on the internet.