How do organisms generate energy when oxygen is not available?

Fermentation releases energy from food molecules by producing ATP.

Explanation:

In the absence of oxygen, fermentation releases energy from food molecules by producing ATP.

Hope this helps...

Extra Information:

And assuming you are using the Biology Foundations Reading and Study Guide Workbook, more information regarding this topic can be found on page 123 (Chapter 10, Cellular Respiration).

answer; ///i believe its: ///(embolus);

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.