nutrient cycles - nitrogen cycle

what are saprobionts?

• microorganisms that feed on dead or decaying organic matter

  • examples include bacteria and fungi

importance of nutrient cycling?

• nutrient recycling is an important process in ecosystems because it allows the nutrients to be continuously reused

what is extracellular digestion?

• when saprobionts excrete enxymes onto dead decaying matter

what do these enzymes from saprobionts do?

• they enzymes break down large, insoluble molecules into smaller, soluble molecules

• these smaller molecules can then be absorbed by the saprobiont

• the saprobiont will then either store the molecules or use them in respiration

role of saprobionts in the nitrogen cycle?

• they are important in the ammonification stage of the nitrogen cycle

• the saprobionts break down organic matter that contains nitrogen such as urea, protein and nucleic acids

• ammonium ions are released as a result of extracellular digestion

• these ions then move onto the next stage of the nitrogen cycle: nitrification

what are the 4 steps in the nitrogen cycle?

• nitrogen fixation

• ammonification

• nitrification

• denitrification

nitrogen fixation?

• atmospheric nitrogen is converted to ammonia by nitrogen-fixing bacteria in the soil

• bacteria are found in the root nodules of leguminous plants

• the bacteria provide a source of ammonium ions for the plants and the plant provides sugars

ammonification?

• when an organism dies or produces waste, it is decomposed by saprobionts

• this releases the nutrients contained inside

• saprobionts decompose the organisms’ biomass by extracellular digestion and inorganic ammonium ions are released into the soil

• ammonification is a by-product of saprobiont nutrition

nitrification?

• ammonium ions that are released from ammonification are converted into nitrates by bacteria in the soil

• nitrifying bacteria firstly convert ammonium ions to nitrites

• another bacteria convert the nitrites into nitrates

denitrification?

• denitrifying bacteria convert nitrates in the soil back into atmospheric nitrogen

• this takes place in anaerobic conditions, such as waterlogged soils