Lecture 10 Flashcards
Biogeochemical Cycles
three carbon isotopes
- carbon-12 (99% of all carbon atoms; stable)
- carbon-13 (1% of all carbon atoms; stable)
- carbon-14 (1 ppt of all carbon atoms; unstable)
Nutrients can be carried long distances via…
winds or waters
biological inputs and removal of carbon in the marine carbon cycle
biological input
- aerobic and anerobic respiration
- fermentation
- upwelling
biological removal
- photosynthesis
- grazing and predation
rhizosphere
the soil layer surrounding actively growing roots that receives carbohydrates from plants
pool vs. flux
- pools are large reservoirs of nutrients (e.g. oceans, the atmosphere, soil)
- fluxes are movements of nutrients between pools (e.g. evapotranspiration, precipitation)
how ectomycorrhizae work
fungi produce a thick sheath of cells that surround the root, but don’t penetrate them, providing root cells with nitrogen from the soil and increasing soil volume due to lots of hyphae
how rhizobium bacteria work
- Bacteria multiply outside the root in response to sugars.
- Bacteria live in root nodules.
- Plants can starve less helpful nodules.
major pools and fluxes of the phosphorus cycle
major pools
- ocean sediments and rock (biggest pool, found as phosphates)
major fluxes
- weathering of rocks
- groundwater runoff
- upwelling
- sedimentation
- tectonic uplift
two anthropogenic activities that increase atmospheric carbon
- burning fossil fuels (80%)
- land use changes; deforestation, agriculture (20%)
three different inputs CO2 enters the atmosphere
- geological inputs (e.g. volcanoes, mid-ocean ridges)
- biological inputs (e.g. cellular respiration)
- anthropogenic inputs (e.g. burning fossil fuels, deforestation)
The nitrogen cycle is an ________ cycle.
atmosphere
two mutualists that provide nitrogen to plants
- rhizobium bacteria: nitrogen-fixers exchange organically useful forms of nitrogen for carbohydrates
- ectomycorrhizae: fungi that exchange soil water and nitrogen for carbohydrates
two ways CO2 leaves the atmosphere
- geological removal (e.g. weathering)
- biological removal (e.g. photosynthesis)
the amount of carbon pollution produced annually by humans
9 gigatons
The phosphorus cycle is a ________ cycle.
sedimentary
major pools and fluxes of the carbon cycle
major pools
- ocean sediment and rock (biggest pool with 99% of carbon)
- the ocean
- land (soil and vegetation)
- the atmosphere
major fluxes
- photosynthesis
- cellular respiration
the isotope of carbon that is decreasing
carbon-13
major pools and fluxes of the hydrological cycle
major pool
- the ocean (biggest pool with 97.5% water)
major fluxes
- evapotranspiration
- precipitation
The biggest factor for the increase in atmospheric carbon over the past 200 years is…
burning fossil fuels (largely unidirectional,, as photosynthesis and cellular respiration offset each other)
the amount of time it can take for a phosphorus atom to return to food webs
100 million years
Photosynthesis ________ atmospheric carbon, whereas cellular respiration ________ atmospheric carbon.
decreases, increases
global biochemical cycle
a linked network of biological and physical processes that moves nutrients through pools within the environment
biological inputs and removal of carbon in the terrestrial carbon cycle
biological input
- aerobic and anerobic respiration
- fermentation
biological removal
- photosynthesis
- grazing and predation
the annual pattern of CO2 concentrations
- CO2 concentrations oscillate seasonally (highest in April, lowest in October), but are increasing steadily
- cellular respiration is constant through the year, but photosynthesis is seasonal
how endomycorrhizae work
fungi do penetrate root cells, forming highly branched arbuscules (but not a thick sheath) and providing root cells with phosphorus from the soil
There is more land in the… (North/South)
North
major pools and fluxes of the nitrogen cycle
major pools
- atmospheric N2
major fluxes
- nitrogen fixation (bacteria and archaea reduce N2 to NH3, making it useful)
- assimilation (primary producers obtain NH3 or NO3- from surroundings)
- denitrification (NO3- is oxidized to N2)
- nitrification (NH3 is oxidized to NO2- or NO2- is oxidized to NO3- for energy)
evidence that humans have increased carbon concentrations
- plants prefer carbon-12 over carbon-13
- neither volcanic gases nor dissolved ocean waters have isotopic carbon ratios that match the increase in atmospheric carbon
- carbon-14 are were decreasing
