Nitrogen cycle and eutrophication

• Biology
• Further Education (Key Stage 5)

What is nitrogen used for in living organisms?

How do plants and animals obtain nitrogen?

The movement of nitrogen gas from the air to leguminous plants using bacteria is known as:

1. Nitrogen fixation
2. Nitrification
3. Ammonification
4. Denitrification

Ammonification in the nitrogen cycle describes the:

1. Conversion of nitrite (NO2-) to nitrate (NO3-)
2. Deamination of amino acids and the release of ammonia (NH3) or ammonium (NH4+)
3. The combination of nitrogen (N2) and hydrogen (H2) to form ammonia (NH3)
4. Release of nitrogen (N2) from ammonia (NH3)

The conversion of nitrates to nitrogen gas by bacteria is called?

1. Nitrification
2. Nitrogen fixing
3. Decomposition
4. Denitrification

Conversion of ammonia to nitrite and then to nitrates is called

1. Ammonification
2. Denitrification
3. Assimilation
4. Nitrification

Name process P

Name process Q

Leguminous crop plants have nitrogen-fixing bacteria in nodules on their roots. On soils with a low concentration of nitrate ions, leguminous crops often grow better than other types of crop. Explain why

Nitrogen-fixing bacteria can convert nitrogen to ammonia [1]

Which is then used to produce proteins / DNA / RNA [1]

Rapid growth in algal populations as a result of the increased nutrients.

As the algae die, there will be a subsequent spike in the numbers of saprotrophic microbes (decomposers).

The high rate of decomposition will result in an increased oxygen demand by saprotrophic bacteria.

The saprotrophs will consume available quantities of dissolved oxygen, leading to deoxygenation of the water supply.

Algal blooms also reduce the amount of light penetrating the surface of the water, which will reduce oxygen production by photosynthetic seaweeds.

Low oxygen causes death of other marine organisms, reducing biodiversity within the ecosystem.

Individual Activity

Complete the exam-style questions on the separate sheet provided.