Life evolves to adapt to its environment. In this respect, explain why life most frequently needs oxygen for survival, rather than the more abundant nitrogen.

Cellular respiration is a fundamental process by which living cells convert nutrients into energy. The most common form of cellular respiration requires oxygen and is known as aerobic respiration. During this process, cells utilize oxygen to break down glucose, a simple sugar, producing ATP, the primary energy currency for cells. This series of reactions takes place within the mitochondria, often referred to as the powerhouses of the cell.

The importance of cellular respiration can be likened to how a power plant generates electricity for a city. Just as a city needs electricity to power homes and businesses, cells require ATP from cellular respiration to carry out essential functions, such as muscle contraction and neural transmission. Without oxygen, the efficiency of this energy-production process drops dramatically, which is why oxygen is so vital for the survival of many organisms.

ATP, or adenosine triphosphate, serves as the energy currency in biological systems. It's produced during cellular respiration when the energy from food is converted into a form that cells can directly use. Think of ATP as a rechargeable battery powering cellular machinery. Every time a phosphate group is removed from an ATP molecule, energy is released, which can then be used for a multitude of cellular activities, including growth, division, and repair.

Moreover, ATP production is critically dependent on the presence of oxygen, especially during the last stages of cellular respiration known as the electron transport chain. This stage produces the bulk of ATP and only occurs with oxygen as the final electron acceptor. Thus, organisms that need a lot of energy for their survival and activity levels are heavily reliant on oxygen to maximize their ATP production.

Nitrogen fixation is the process that changes inert atmospheric nitrogen gas (N₂) into a form of nitrogen usable by living organisms, like ammonia (NH₃). While nitrogen is abundant, making up about 78% of Earth's atmosphere, it's mostly inaccessible to most organisms in its gaseous form due to the strong triple bond between the nitrogen atoms.

Certain bacteria, known as diazotrophs, have the unique ability to perform nitrogen fixation. These bacteria live freely in the soil or in symbiotic relationships with plant roots, especially in legumes. Through this symbiotic partnership, plants provide carbohydrates to the bacteria, and in return, the bacteria fix atmospheric nitrogen into compounds that plants can use to make proteins and nucleic acids. This biological process is essential for the nitrogen cycle and supports the growth of plants, which are foundational to most food chains on Earth.

Biological processes are the complex series of events, biochemical reactions, and physiological mechanisms that occur within living organisms. These processes encompass everything from the very basic, like cellular respiration and ATP production which we have discussed, to more complex mechanisms like development, growth, reproduction, and response to stimuli.

Each biological process serves a specific role that contributes to the organism's survival and function. For instance, photosynthesis in plants converts solar energy into chemical energy, which is then passed on through the food chain. Similarly, the immune system works to protect the organism from infection. The intricate coordination of these processes is vital for the maintenance of life. Oxygen, again, plays a critical role by enabling efficient energy production, while nitrogen fixation supports growth and the maintenance of genetic material in organisms.