Energy Food And Nutrient Cycles Flashcards
How is energy converted to chemical energy?
Enters mostly as sunlight then converted. By autotrophic organisms then passed to heterotrophic organisms.
Explain the global energy budget
Infinite. Either reflected absorbed or refracted. Only small fraction gets used by primary producers.
Why does only 10% make it to the next level in an ecosystems energy budget?
Decomposers - heat, waste and dead matter.
Regional primary production?
Changes where you are. Oceans are low. Rest on land however water issue on land. Tropics highly productive.
Secondary production?
The amount of chemical energy in consumers food covered to their own biomass - generally insufficient. 95% of food gets used for respiration.
Why is ecosystem cycling of chemicals?
Ecosystem energy is not limited but chemical energy is. Therefore life depends on recycling of these essential compounds. Both biotic and a biotic
Explain the ratio of evaporation and precipitation in the water cycle
Evaporation exceeds precipitation
However other way round on land - therefore surface water and ground water
Over sea evaporation forms most water vapour
Explain the carbon cycle
Photosynthesis and respiration account for the majority of terrestrial ecosystem carbon movement
Annually a seasonally pulse of carbon dioxide is associated with lower photosynthesis rates during the northern hemisphere winter which then declines over summer
Globally the return of carbon to the atmosphere via respiration closely matches removal due to photosynthesis
Explain the nitrogen cycle
The addition to nitrogen to ecosystem and it’s return via denitrification involves relatively small amounts compared to local recycling
The dominant pathway for nitrogen entering ecosystem via nitrogen fixation carried out by a few prokarkyotes
Nitrogen fixation converts n2 to ammonia which as most soils are acidic is converted to ammonium available for plant uptake. Can also be converted in the atmosphere
Bulk of ammonium is not taken up by plants and converted to organic nitrogen
Animals can assimilate only organic nitrogen sources
Overall the majority of nitrogen cycling involves the nitrogenous compounds in water and soil. Not the gas
What is nitrogen?
Triple bond, very stable. Difficult to break down but lightning can.
Makes up majority of atmosphere but in primary unusable form c2 gas
Explain the phosphorus cycle
Cycles locally and atmospheric component. Occurs in 1 important form inorganic po4 3-.
Generally small loses due to leaching are balanced by gains from rock weathering.
In both terrestrial and aquatic systems phosphorus is cycled in food webs
Lost from aquatic ecosystems via precipitation or through settling debris where it may be locked away in sediment layers
