When a single creature, or a whole species, changes in order to better fit their environment it is called

evolution

explanation:

when there's changes in the environment, the creatures have to adapt in order to be able to survive. this causes genetic mutations that will provide the creature with advantageous traits to make it more competitive. over time, these changes might so drastic, that the creature doesn't look anything like its ancestors. this changes in order to better fir the environment are called evolution.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.