Nutrients cycles

Question 1

What are saprobionts?

Answer 1

Organisms that beak down remains of dead plants/animals and waste matter. It allows important chemical elements to be recycled. They secrete enzymes, digest food externally and absorb nutrients. Organic molecules are broken down into inorganic ions.

Question 2

What is mycorrhizae?

Answer 2

A symbiotic relationship between fungi and roots.
- the fungi are made from long, thin strands (hyphae) which connect roots
- hyphae increase the surface area for fungi to obtain organic compounds

Question 3

Why do plants and animals need nitrogen?

Answer 3

To make protein and nucleic acid (RNA and DNA)

Question 4

What are the 4 stages of the nitrogen cycle?

Answer 4

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

Question 5

Explain what happens during nitrogen fixation

Answer 5

Nitrogen gas is turned into nitrogen containing compounds. It is carried out by rhizobium. Nitrogen is turned into ammonia and then turned into ammonium ions.

Question 6

What is rhizobium?

Answer 6

A bacteria found inside root nodules of leguminous plants that form a mutualistic relationship with plants

Question 7

Explain what happens during ammonification

Answer 7

Nitrogen and animal waste containing nitrogen compounds are turned into ammonia and then ammonium ions by sapriobionts

Question 8

Explain what happens during nitrification

Answer 8

Ammonium ions in the soil are changed into nitrogen compounds that can be used by plants. Nitrosomonas (nitrifying bacteria) change ammonium ions into nitrites and Nitrobacter change nitrites into nitrates

Question 9

Explain why happens during denitrification

Answer 9

Nitrates are converted into nitrogen gas by denitrifying bacteria. Happens in anaerobic conditions

Question 10

Why do animals and plants need phosphorus?

Answer 10

To make biological molecules such as phospholipids, DNA and ATP

Question 11

Explain the phosphorus cycle

Answer 11

1. Phosphate ions in rocks are released into soil by weathering. It is taken into plants by their roots
2. Mycorrhizae increases the rate at which phosphorus can be assimilated
3. Phosphate ions are transferred through food chains and lost in waste products
4. As plants and animals die Saprobionts break them down releasing phosphate into the soil
5. Weathering of rocks and guano also release phosphate ions