TLDR: An aerobic organism is a living thing that thrives in an environment with oxygen. It can use oxygen to produce energy more efficiently than organisms that don't need oxygen.
An aerobic organism is a living thing that can survive and grow in an environment with oxygen. This includes many different types of organisms, from bacteria to plants to animals. The ability to use oxygen for energy production is called aerobic respiration, and it provides several benefits to these organisms. Aerobic respiration produces more energy (in the form of ATP) compared to anaerobic respiration, which is the process used by organisms that don't require oxygen.
In aerobic respiration, an enzyme called ATP synthase works together with an electron transport chain to produce ATP. Oxygen acts as the final electron acceptor in this process. This means that oxygen helps to generate ATP, which is the energy currency of cells. Aerobic organisms have evolved to take advantage of this efficient energy production method.
Interestingly, scientists have discovered aerobic microorganisms that can survive in very old sediments deep below the seafloor. These microorganisms have been found in sediments that are up to 101.5 million years old! This discovery suggests that aerobic organisms can have incredibly long lifespans.
There are different types of aerobic organisms based on their oxygen requirements. Obligate aerobes are organisms that need oxygen to grow and survive. They use oxygen to oxidize substrates (such as sugars and fats) and generate energy. Facultative anaerobes can use oxygen if it is available, but they also have alternative methods of energy production that don't require oxygen. Microaerophiles require oxygen for energy production, but they are harmed by high concentrations of oxygen. Aerotolerant organisms, on the other hand, do not use oxygen for energy production, but they are not harmed by it.
In summary, aerobic organisms are living things that can survive and grow in an oxygenated environment. They have evolved to use oxygen for efficient energy production through aerobic respiration. This ability gives them an advantage over organisms that don't require oxygen. There are different types of aerobic organisms based on their oxygen requirements, ranging from those that need oxygen to those that can tolerate it but don't use it for energy production.