Anaerobic respiration occurs without oxygen and much less frequently than aerobic respiration. Human bodies use both types of respiration. Humans do aerobic respiration unless they are short of ...

The rise of oxygen levels led to the evolution of aerobic respiration, a process that uses oxygen to convert food into energy. Today, most land and aquatic organisms – including humans – need ...

This article explores how nitrogen becomes available to organisms and what changes in nitrogen levels as a result of human activity ... Some of these bacteria are aerobic, others are anaerobic ...