Water is considered hypoxic (Lacking oxygen) if it contains 2 mg/l or less of dissolved oxygen. Think of the food chain that is exists in the Gulf of Mexico: what are the types of organisms that likely live at the bottom of the Gulf, where the water is most hypoxic? How can lack of oxygen affect them? Which cellular process are affected by lack of oxygen?

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

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.