Nutrient Cycles

Question 1

What is decomposition?

Answer 1

The break down of dead organic matter by saprobiants.

Question 2

How do saprobiants break down dead organic matter?

Answer 2

1. They feed on the remains of dead plants and animals and their waste products and break them down.
2. They secrete enzymes that digest their food externally and they take the nutrients they need and leave the rest in the soil.

Question 3

What is the role of the mycorrhizae?

Answer 3

The fungi are made up of long thin strands called hyphae thar attach to the roots of plants and increase their surface area for the uptake of water and mineral ions and in exchange the fungi get important biological molecules like glucose.

Question 4

Why do plants need nitrogen?

Answer 4

To make proteins and nucleic acids.

Question 5

Why do bacteria need to convert nitrogen in the air into nitrogen containing compounds?

Answer 5

Because plants can’t use the nitrogen that is inthe air.

Question 6

What are the steps of the nitrogen cycle?

Answer 6

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

Question 7

What happens during nitrogen fixation?

Answer 7

Nitrifying bacteria turns nitrogen in the atmosphere into ammonia. This turns into ammonium ions in the soil.

Question 8

What happens during ammonification?

Answer 8

Saprobiants break down nitrogen compounds in dead organisms into ammonia which then turns into ammonium ions in the soil.

Question 9

What happens during nitrification?

Answer 9

When ammonium ions in the soil are turned into nitrites and then nitrates by nitrifying bacteria which plants can then use.

Question 10

What happens during denitrification?

Answer 10

Nitrates in the soil are converted into nitrogen gad by nitrifying bacteria.

Question 11

Why are fertilisers needed in agricultural systems?

Answer 11

The nutrients in the soil are used for crop growth but when the crops are removed since the dead organic matter in not broken down by saprobiants and the nutrient aren’t returned to the soil fertilisers are needed to replace those nutrients with new ones.

Question 12

What are inorganic fertilisers?

Answer 12

These contain pure chemicals

Question 13

What are organic fertilisers?

Answer 13

These contain manure and composted vegetables.

Question 14

Why do fertilisers increase productivity?

Answer 14

They replace lost minerals so more energy in the ecosystem can be used for growth and thar means the NPP increases.

Question 15

What are the environmental problems with using nitrogen fertilisers?

Answer 15

1. Leaching.
2. Eutrophication

Question 16

What is leaching?

Answer 16

When water soluble substances like inorganic water are washed away and they can go into water sources and cause eutrophication.

Question 17

What happens during eutrophication?

Answer 17

When nutrients leach into water sources they cause algae to grow a lot and this creates an algae bloom. The algae bloom blocks off the sunlight meaning that the plants underneath can’t use light energy to photosynthesis and they die. This mean the bacteria feed on the dead animal matter and grow in number. Because there are more bacteria taking in oxygen for aerobic respiration the oxygen concentration decreases and aquatic animals die.