OCR A2 Biology: The Nitrogen Cycle

Question	Answer
Why do plants and animals need Nitrogen?	To make proteins and nucleic acid for growth
What is Nitrogen Fixation?	Nitrogen gas in the atmosphere is converted to ammonia by Rhizobium
What is ammonification?	Nitrogen compounds from dead organisms or animal waste are turned into ammonium compounds by decomposers.
What is Nitrification?	Ammonium compounds in the soil are changed into nitrogen compounds that can be used by plants.
Describe the process of Nitrification	1. Nitrosomonas bacteria change ammonium compounds into nitrites 2. Nitrobacter convert nitrites into nitrates
What is denitrification?	Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria.
Describe the process of denitrification	They use nitrates in the soil for respiration and produce nitrogen gas. This happens under anaerobic conditions.
What natural way can nitrogen enter an ecosystem?	By lightning
What unnatural way can nitrogen enter an ecosystem?	Artificial fertilisers
What is the order of The Nitrogen Cycle	1. Nitrogen Fixation 2. Ammonification 3. Nitrification 4. Denitrification (Or back to 2)

Resource summary

	Created by hannawin98 over 8 years ago