23.3 - Recycling Within Ecosystems

Question 1

What is decomposition?

Answer 1

• chemical process where a compound is broken down into smaller molecules
• Carbon or Nitrogen cannot be used directly in its organic form, and must be processed into inorganic elements which are more usable and returnable to the environment

Question 2

What is a decomposer?

Answer 2

• Organism that feeds and breaks down dead matter, turning organic compounds into inorganic ones that are available.
• They are saprotrophs as they obtain energy from dead/waste organic material.
• Digest food externally by secreting enzymes which break down complex molecules to soluble small ones which are then absorbed

Question 3

What is a detritivore?

Answer 3

Help to speed up decay process by feeding on dead/decaying material and they break it into smaller pieces to provide a larger surface area for the decomposer

Question 4

Describe Nitrogen fixation

Answer 4

• Nitrogen fixing bacteria contain enzyme Nitrogenase
• Nitrogenase combines atmospheric nitrogen with hydrogen to make ammonia
• Azotobacter is a free-living soil bacteria
• Many bacteria like Rhizobium live inside root nodules.
• symbiotic mutualistic relationship with plant because plant gains amino acids due to fixing nitrogen bacteria, and bacteria gain carbohydrates produced by plant for energy

Question 5

Describe Nitrification

Answer 5

Process of turning ammonium compounds into nitrogen containing molecules for plants to use. Involves free-living bacteria in the soil

• oxidation reaction in well aerated soil
  1) Nitrifying bacteria oxidise ammonium compounds into nitrites
  2) Nitrobacter oxidises nitrites into nitrates
  Nitrates are highly soluble and so can enter the plant

Question 6

Describe Denitrification

Answer 6

• when oxygen is unavailable, denitrifying bacteria convert nitrates in nitrogen gas
• only occurs under anaerobic conditions
• bacteria use the nitrates as a source of energy for respiration and N2 is released

Question 7

What is ammonification?

Answer 7

Process where decomposer convert nitrogen-containing molecules in dead organisms into ammonium compounds

Question 8

The nitrogen cycle

Answer 8

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