Phosphorus Cycle

Question 1

Describe the phosphorus cycle.

Answer 1

1. Phosphate ions are released into the soil from rocks by weathering
2. Phosphate ions are taken up by plants root cells by active transport
   
   • mycorrhizae increase the rate of uptake
   • plants use the phosphate ions to make phospholipids, ATP, DNA, RNA, RuBP etc.
3. Phosphate ions are transferred through food chains
4. Phosphate ions are lost from animals through egestion and excretion
5. During decomposition, saprobionts release phosphate ions into the soil
6. Weathering also releases phosphate ions into seas, lakes and rivers
7. Phosphates dissolved into water are taken up by aquatic plants/ algae and make organic molecules
8. Fish eat aquatic plants and algae, consuming the organic molecules which contain phosphates
9. Sea birds eat fish, consuming the phosphate containing organic molecules
10. Birds excrete guano which is highly concentrated in phosphate ions directly into the soil