Variations in elevation of a land surface is

Variations in elevation of a land surface is relief (or terrain)

Relief also known as terrain is the variations in elevation of a land surface. The relief of an area is the difference in elevation between the highest and lowest dimensions of the area. Relief helps to indicate the direction, height, and angle of slope of many physical geographical features such as plains and mountains in a particular region on the earth surface.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.