Question

respond to the following two questions: • what is the nitrogen cycle? • why do living organisms depend on nitrogen fixation for their existence? you may start your answers with: • the nitrogen cycle is... • organisms are unable to absorb nitrogen gas because...

Explanation:

1. For the nitrogen cycle: The nitrogen cycle is the biogeochemical process by which nitrogen is converted between its various chemical forms in the environment, involving processes like nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. It cycles nitrogen through the atmosphere, soil, water, and living organisms.
2. For the dependence on nitrogen fixation: Organisms are unable to absorb nitrogen gas (N₂) because the triple bond in N₂ is very strong, making it chemically inert and not directly usable by most organisms. Nitrogen fixation converts atmospheric nitrogen into ammonia (NH₃) or other usable nitrogen compounds (like nitrates, nitrites) that can be taken up by plants (and then passed up the food chain). Since nitrogen is essential for making proteins, nucleic acids (DNA, RNA), and other vital biomolecules, organisms depend on nitrogen fixation to obtain a usable form of nitrogen for growth, metabolism, and survival.

Answer:

• The nitrogen cycle is the biogeochemical process where nitrogen transitions between atmospheric (N₂), organic (e.g., in proteins), and inorganic (e.g., ammonia, nitrates) forms via processes like fixation, nitrification, assimilation, ammonification, and denitrification, cycling through air, soil, water, and organisms.
• Organisms are unable to absorb nitrogen gas because the strong triple bond in N₂ makes it unreactive; nitrogen fixation converts N₂ to usable forms (e.g., ammonia, nitrates) needed for biomolecules (proteins, nucleic acids), so organisms depend on it for growth, metabolism, and survival.