15. Nutrient cycles

• What biological molecules contain nitrogen?

  Proteins,

  nucleic acids,

  ATP
• Why is nitrogen not available to most organisms in its gas state?

  It is inert or unreactive
• What is the first step of the nitrogen cycle?

  Nitrogen fixation
• What bacteria is used during nitrogen fixation?

  Nitrogen fixing bacteria
• What do nitrogen fixing bacteria do?

  Convert nitrogen gas into ammonia or ammonia ions
• where can nitrogen fixing bacteria be found?

  Swellings on the roots of plants called legumes
• What is nitrification?

  Ammonia ions converted into nitrates
• What bacteria carries out nitrification

  Nitrifying bacteria
• What are the two steps in nitrification?

  Oxidation of ammonia to nitrite

  Oxidation of nitrates to nitrates
• How do plants take up nitrates?

  Active transport
• What are nitrates used for when in plants

  To synthesise molecules, such as protein or DNA
• What bacteria carries out decomposition

  Saprobiotic,
• What happens during ammonification?

  Separate bond, convert organic nitrogen to ammonia
• What is denitrification?

  Denitrification is the process by which nitrates are converted into nitrogen gas, removing nitrogen from the soil or water.
• How can we reduce denitrification?

  Decrease fertilizer use.

  aerate the soil
• What biological molecules contain phosphorus?

  Nucleic acids, ATP, phospholipids.
• Explain the phosphorus cycle

  Dead animals or plants are decomposed by saprobionts. They release, phosphate ions into lakes, rivers, or oceans, where they dissolve. Some of these phosphate ions are then absorbed by plants to synthesise biological molecules. Some of the dissolved phosphate can by sedimentation form rocks.
• What is Mycorrhizae?

  Symbiotic fungi.

  grows on plant roots
• What does mycorrhizae do?

  Increases the uptake of water and ions for the plant by increasing surface area
• Why do we need fertilisers?

  Intensive food production results in nutrients being lost from the soil
• What are the two types of fertilisers?

  Natural and artificial
• What is natural fertiliser?

  Consists of organic plant matter which releases mineral ions as it decays- slow release
• What is artificial fertiliser?

  Manufactured concentrated mineral ions in an inorganic soluble ready to use form- quick release
• What happens if too much fertiliser is added

  Causes a decrease in water potential, so water leaves the plants stunting growth
• What are the environmental consequences of using artificial fertiliser?

  Leeching, which leads to eutrophication
• What is eutrophication?

  Eutrophication is the process of excessive nutrient enrichment in a body of water, leading to an overgrowth of algae and other aquatic plants. This can disrupt the natural balance of the ecosystem, depleting oxygen levels and harming fish and other organisms.