Energy Transfers in and Between Organisms: Nutrient Cycles - Nitrogen Cycle Flashcards
1
Q
Why do organisms need nitrogen?
A
- Plants and animals need nitrogen to make proteins and nucleic acids (DNA and RNA)
2
Q
What are the four main processes in the nitrogen cycle?
A
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
3
Q
Draw the nitrogen cycle
A
4
Q
What is nitrogen fixation?
A
- When nitrogen gas in the atmosphere is turned into ammonium ions by bacteria called Rhizobium
- Rhizobium are found in the root nodules of leguminous plants (e.g peas, beans)
- Plants absorb the ammonium ions to make nitrogen compounds
5
Q
What type of relationship do Rhizobium and plants have?
A
- Mutualistic relationship
- Both species benefit
6
Q
Which bacteria is involved in nitrogen fixation?
A
- Rhizobium
7
Q
What is an ammonium ion?
A
- NH4^+
8
Q
What is ammonification?
A
- When nitrogen compounds from dead organisms and animal waste are turned into ammonia, then ammonium ions by saprobionts
9
Q
What is nitrification?
A
- When ammonium ions in soil are changed into nitrates, so they can be used by plants
- First, nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
- Then other nitrifying bacteria called Nitrobacter change nitrites into nitrates
10
Q
Name the bacteria involved in nitrification in order
A
- Nitrosomonas
- Nitrobacter
11
Q
Give the formula of nitrites
A
- NO2^-
12
Q
Give the formula of nitrates
A
- NO3^-
13
Q
Which are produced first in nitrification: nitrites or nitrates?
A
- First, nitrites (NO2^-)
- Second, nitrates (NO3^-)
14
Q
What is denitrification by bacteria?
A
- When denitrifying bacteria convert nitrates in soil into nitrogen gas
- They use nitrates to carry out anaerobic respiration and produce nitrogen gas
15
Q
Where may dentrification occur (anaerobic conditions)?
A
- Waterlogged soils
