
<h2>Fixation</h2>
Nitrogen in its gaseous form (N2) can’t be used by most living things. It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things:
<h3>Biologically: </h3>
Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.
<h3>Through lightning: </h3>
Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.

I think the answer is two
Answer:
An organ system is a group of organs that work together as a biological system to perform one or more functions. Each organ does a particular job in the body and is made up of distinct tissues.
Explanation:
DNA is copied because it cannot fit through the nuclear membrane and travel down to the ribosome.
So it is transcribed (translated) to messenger RNA (mRNA). The mRNA can fit through the nuclear membrane and travel down to the ribosome where proteins can be made.
This is why we cannot send the entire DNA molecule itself, it is simply too big to fit. This is why mRNA is extremely important for amino acid production.