ecosystem y2

• Who is the instructor in the video about the nitrogen cycle?

  Miss Esther
• Why is the nitrogen cycle important?

  It helps convert nitrogen gas for plants and animals
• What percentage of the atmosphere is made up of nitrogen gas?

  30 percent
• Why can't animals and plants obtain nitrogen through gas exchange?

  Nitrogen gas has a triple bond, making it inert
• What role do microorganisms play in the nitrogen cycle?

  They break nitrogen gas bonds to convert it
• How do plants absorb nitrogen-containing substances?

  Through active transport in the roots
• Which biological molecules contain nitrogen?

  Proteins, ATP, DNA, and RNA
• What are the four key processes of the nitrogen cycle?

  • Ammonification
  • Nitrification
  • Nitrogen-fixing
  • Denitrification
• What is ammonification in the nitrogen cycle?

  It is the creation of ammonium from organic matter
• What is nitrification?

  It is the conversion of ammonium to nitrates
• What are the two stages of nitrification?

  Conversion of ammonium to nitrites, then nitrates
• How do plants absorb nitrates?

  By active transport from the soil
• What happens to nitrogen when animals and plants die?

  Decomposers break down proteins into nitrogen compounds
• What is the role of decomposers in the nitrogen cycle?

  They digest dead matter and release nitrogen
• What is denitrification?

  Conversion of nitrates back into nitrogen gas
• Why is denitrification undesirable in agriculture?

  It leads to loss of nitrogen from the soil
• What conditions promote denitrification?

  Low oxygen levels in waterlogged soil
• What is the oxidation process in nitrification?

  Ammonium to nitrite to nitrate is oxidation
• What must be specified when discussing decomposers in an exam?

  The specific nitrogen-containing compound involved
• What nitrogen-containing compound is found in animal urine?

  Urea
• What nitrogen-containing compound is found in dead plant matter?

  Proteins
• Who is the presenter of the A Level Biology video on the phosphorus cycle?

  1. Ik
• What is phosphorus used for in organisms?

  It is essential for DNA, RNA, and ATP
• Why is the phosphorus cycle important?

  It is crucial for essential biological molecules
• What is the main source of phosphorus in the cycle?

  Phosphate ions in rocks
• How does the phosphorus cycle differ from the carbon and nitrogen cycles?

  Phosphorus does not exist as a gas
• What are mycorrhizae?

  Fungi associated with plant roots
• What advantage do mycorrhizae provide to plants?

  They increase surface area for water absorption
• How do plants benefit mycorrhizae?

  Plants provide carbohydrates to the fungi
• What are the stages of the phosphorus cycle?

  1. Phosphate ions in water absorbed by plants
  2. Plants incorporate phosphate into biological molecules
  3. Animals digest plants and absorb phosphate
  4. Excretion and decomposition release phosphate
  5. Guano and animal remains contribute phosphate
  6. Erosion of rocks releases phosphate into water
  7. Sedimentation creates rocks containing phosphate
• What is guano and its significance in the phosphorus cycle?

  Guano is rich in phosphorus from bird waste
• What happens to phosphate ions after animal excretion?

  They can return to oceans or soil
• How does sedimentation contribute to the phosphorus cycle?

  It creates rocks that contain phosphate ions
• What role do fertilizers play in the phosphorus cycle?

  They add phosphate to the land
• What is the final step in the phosphorus cycle?

  Phosphate ions return to oceans and soil