23.3 Recycling Within Ecosystems Flashcards
Decomposition
Chemical process where a compound is broken down into smaller molecules or its constituent elements
Decomposer
Organism that feeds on and breaks down dead plant or animal matter
What does a decomposer do?
Turn organic compounds into inorganic ones
What kind of organisms are decomposers?
Saprotrophs - obtain energy from dead or waste organic material
How do decomposers break down food?
Secrete enzymes onto dead organisms
Enzymes break down complex organic molecules into simpler soluble molecules
The decomposer absorbs these nutrients
Detritivores
Speed up decay process by feeding on detritus - break it down into smaller pieces to increase SA
Why is nitrogen important?
Making amino acids and proteins
Nucleic acids
When can nitrogen be used by plants?
Needs to be combined with O2 and H2
Examples of nitrogen fixing bacteria
Aztobacter and Rhizobium
How do nitrogen fixing bacteria work?
Contains enzyme nitrogenase - combines N2 with H2 to form ammonia NH3
Where are aztobacter found?
In the soil - it’s a free living soil bacterium
Where are rhizobium found?
Inside root nodules of leguminous plants such as peas, beans and clover
Symbiotic mutualistic relationship between rhizobium and the plant
Plant gains amino acids from rhizobium by fixing N2
Bacteria gains carbohydrates produced by the plant during photosynthesis (used as energy source)
Nitrification
Process where ammonium compounds are converted into nitrogen containing molecules that can be used by plants
Free living bacteria in the soil called nitrifying bacteria are involved
In what conditions does nitrification take place?
Oxidation reaction so occurs in well aerated soil
Two steps of nitrification
Nitrifying bacteria such as nitrosomonas oxidise ammonium compounds into nitrites (NO2-)
Nitrobacter oxidise NO2- into NO3- (nitrates)
Denitrification
In the absence of oxygen (waterlogged soils), denitrifying bacteria convert nitrates in the soil back to nitrogen gas
Occurs in anaerobic conditions
Bacteria use nitrates as a source of energy for respiration to produce N2
Ammonification
Process by which decomposers convert nitrogen containing molecules in dead organisms, faeces and urine into ammonium compounds
Why is carbon important?
Component of all major organic molecules such as fats, carbohydrates, and proteins
How is CO2 returned to the atmosphere?
There us some dissolved in seas and oceans
Combustion
Respiration of plants and animals
Decomposition
How are fossil fuels formed?
When living organisms die, carbon compounds are released through decomposition
If dead organic matter accumulates in areas without decomposers, carbon becomes trapped and eventually form fossil fuels
Why do CO2 levels fluctuate?
Photosynthesis only takes place during the day, remove CO2
Respiration takes place day and night
CO2 levels are higher at night than during the day
More photosynthesis on a warmer day - less CO2 in atmosphere
Why have atmospheric CO2 levels increased over the last 200 years?
Combustion of fossil fuels
Deforestation - less photosynthesis, burning of felled trees
How does temperature affect CO2 dissolved in seas?
Higher temperatures - less CO2 dissolved
Reduce carbon bank in the oceans and more CO2 in the atmosphere
