Nutrient cycles (BIOL4) Flashcards
What are the processes involved in the nitrogen cycle?
Nitrogen fixation
Ammonification
Nitrification
Denitrification
Features of nitrogen fixation in the nitrogen cycle
- Nitrogen gas in atmosphere turned into ammonia by nitrogen-fixing bacteria (Rhizobium), can be used by plants
- Rhizobium found inside root nodules of leguminous plants (peas etc)
- Form mutualistic relationship w/ plants - provide plant w/ nitrogen compounds, plant provides carbs
Features of ammonification in the nitrogen cycle
- Nitrogen compounds from dead organisms (animals, plants) are turns into ammonium compounds by decomposers/saprophytes (saprobiotic nutrition)
- Animal waste contains nitrogen also turned into ammonia
Features of nitrification in the nitrogen cycle
- Ammonium compounds in soil changed into nitrogen compounds to be used by plants
- Nitrifying bacteria convert ammonium compounds into nitrates
- Nitrifying bacteria (Nitrobacter) convert nitrites into nitrates
Features of denitrification in the nitrogen cycle
- Nitrates in soil converted into nitrogen gas by denitrifying bacteria - use nitrates in soil to respire and make nitrogen gas
- Takes place under anaerobic conditions e.g waterlogged soils
How can nitrogen fertilisers cause eutrophication?
- Nitrates leach from fertilised fields stimulate algal bloom in ponds/rivers
- Large amount of algae block light from reaching plants below
- Plants die as unable to photosynthesise
- Bacteria feed on dead plant matter Increased no. of bacteria reduce oxygen conc in water by aerobic respiration
- Organisms/animals die due to lack of dissolved oxygen
What are the processes involved in the carbon cycle?
Photosynthesis
Respiration
Decomposition
Combustion
Features of the carbon cycle
- CO2 absorbed by plants when photosynthesising to become carbon compounds in plant tissue
- Primary consumers eat plants and pass C onto secondary & tertiary consumers when eaten
- Living organisms die and digested by decomposers - take in C
- C returned into air when organisms respire, producing CO2
- If dead matter not decomposed, C turn into fossil fuels over mill years by heat/pressure C in fossil fuels released when burnt - combustion
How does respiration and photosynthesis cause daily changes in CO2 concentration?
- Respiration during day and night
- Photosynthesis only during daylight CO2 conc. falls during day as photosynthesis removes it CO2 conc. inc. at night as no photosynthesis
How does respiration and photosynthesis cause yearly changes in CO2 concentration?
- Most plants grow in summer (more light/temp) most photosynthesis occurs
- CO2 conc. falls during summer as more removed due to more plants photosynthesising
- CO2 conc. inc during autumn/winter as less being removed - fewer plants photosynthesising
Define global warming
The increase in average global temperature
Human activity caused this by enhancing greenhouse effect - effect of greenhouse gases absorbing outgoing energy, so less lost to space
Why does CO2 concentration change at different heights above ground of forest over 24 hours?
- Dark during night, so plants respire
- Light needed for photosynthesis, so CO2 conc inc.
- In light, rate of photosynthesis greater than respiration
- Net uptake of CO2 greater than production
What is the effect of greenhouse gas CO2 on global warming?
- CO2 conc. inc. as more fossil fuels burnt, releasing CO2
- Inc. by destruction of natural sinks (keep CO2 out of air)
- Trees store CO2, release when decomposers b/d or burnt
How does greenhouse gas methane cause global warming?
- More release into atmosphere as fossil fuels are being extracted
- Cattle giving off methane gas
- Can be released from natural stores e.g frozen ground when they thaw
What are the effects of global warming on crop yield?
- CO2 limiting factor for photosynthesis
- Inc. of CO2 means crops grow faster, inc. crop yields
