energy and ecosystems

• Phosphate cycle

  Rocks contain phosphate. Harsh weather conditions break down rocks, releasing phosphate into the soil.

  Some phosphate is absorbed by plants to make phosphate-containing compounds like ATP.

  Plants are eaten by animals, which can then make their own phosphate-containing compounds.

  Both plants and animals die, and animals also excrete.

  The waste of animals and plants is broken down by saprobionts, releasing phosphate back into the soil.

  Some phosphate moves throughout the soil to bodies of water, like the sea.

  Over thousands of years, phosphate is used to form new rocks.
• Saprobionts release phosphates into the soil. What happens to these phosphates?

  They move throughout the soil to bodies of water, like the sea.

  They are reabsorbed by plants to make phosphate-containing compounds.
• Plants absorb phosphate to form biological molecules containing phosphorus. What might the plant make?

  ATP

  DNA
• Describe how dead organisms are utilised in the phosphorus cycle.

  Dead organisms within the soil attract saprobionts.These saprobionts break down phosphorus-containing compounds to phosphate.The phosphate is either moved into bodies of water to form rocks, or directly absorbed by plants through the soil.
• The majority of plants obtain nitrogen in the form of…

  nitrate
• what are the 2 types of nitrogen-fixing bacteria?

  mutualistic and free-living
• what is ammonia converted into in the soil?

  ammonium ions
• Describe how nitrogen gas is converted into ammonium ions during the nitrogen cycle.

  Free-living nitrogen-fixing bacteria exist in the soil and convert nitrogen gas to ammonia.This ammonia is then converted to ammonium ions in the soil.
• In the nitrogen cycle, nitrogen gas is first converted to ammonium ions.In the soil, Nitrosomonas convert the ammonium ions into nitrate.Nitrobacter then convert this nitrogen-containing compound to 

  nitrates.The processes carried out by these bacteria are collectively called 

  nitrification
• In the nitrogen cycle, describe how nitrate is converted to nitrogen gas.

  The process of converting nitrate to nitrogen gas is known as denitrification. This is carried out by denitrifying bacteria undergoing anaerobic respiration.
• nitrogen cycle

  1. Free-living nitrogen-fixing bacteria and mutualistic nitrogen-fixing bacteria convert nitrogen gas into ammonia. When released into water in the soil, ammonia forms ammonium ions.
  2. Nitrifying bacteria convert ammonium ions into nitrate. This process requires oxygen.
  3. Saprobionts break down nitrogen-containing compounds, such as DNA, in waste material to ammonia. When released into water in the soil, ammonia forms ammonium ions. - ammonification
  4. Denitrifying bacteria convert nitrate to nitrogen gas when they carry out anaerobic respiration. - denitrification
• Plants absorb nitrate to form biological molecules containing nitrogen. Which of the following might the plant make from nitrogen?

  Amino acids

  Nucleic acids
• Describe how dead organisms are utilised in the nitrogen cycle.

  Saprobionts break down nitrogen-containing compounds in waste material (such as DNA) to form ammonia.When released into water in the soil, ammonia forms ammonium ions which can then be converted into nitrate.
• Which two processes produce ammonium ions in the nitrogen cycle?

  nitrogen fixation and ammonification
• The phosphorus cycle is slower as phosphate is obtained from mountain-rock, which eventually dissolves into the soil.

  The nitrogen cycle is quicker as nitrogen is readily available. It can be obtained directly from the atmosphere and absorbed into the soil.