Bio 1215- Chapter 18
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what is an ecosystem? what do ecosystem ecologists study?
- ecosystem= community with abiotic factors
- ecologists study energy flow and chemical cycling
In food webs, energy and chemicals flow between different ______________.
In food webs, each energy transformation is ___________.
what is the function of decomposers?
return chemicals need by primary producers
most decomposition is done by which 2 organisms?
- prokaryotes (bacteria)
- and fungi (basidiomycetes)
what determines the energy budget for the whole ecosystem?
rate of photosynthesis
what is the gross primary production (GPP)?
- amount of light energy converted to chemical energy (sugar) per unit time
- ~1% of sunlight converted
what is net primary productivity (NPP)? what does it determine?
- GPP minus energy used for respiration
- determines what is available to higher trophic levels
NPP may be as little as ____ of GPP
Large plants have lower NetPP: GrossPP. why?
plants have more non-photosynthetic tissue to support
Is NPP equal throughout all ecosystems?
NPP higher in some ecosystems than others
what are the 2 factors influencing primary productivity?
- rain, temperature, light
- nutrient limitations
In which biomes are rain, temperature, and light high, therefore have a high NPP?
Tropical forests (tropics)
what are the nutrient limitations in marine ecosystems?
in marine ecosystems the limiting elements are usually nitrogen (N), phosphorous (P) o maybe Iron (Fe)
what is eutrophication?
process of making a water body highly "organic" because of the arrival to high levels of nutrients
Energy transfer between trophic levels is usually ____ efficient.
- < 20% efficient
- that's why food chains only have a few steps
More energy is available to which trophic levels?
lower trophic levels
Species at the top of the trophic levels are: (3)
- less numerous
- widely spaced
- more prone to disturbance (or extinction)
where is most of the water in the water cycle found?
>97% in oceans; 1% in atmosphere
what is the water cycle? (5)
- precipitation over land
- runoff and groundwater into sea
- evaporation from the sea
- net movement of water vapor by wind
- transport over the land
what is one method of the carbon cycle? (6)
- photosynthesis of plants, algae, cyanobacteria
- plants eaten by primary consumer
- primary consumer eaten by secondary consumer
- CO2 in atmosphere
The carbon cycle also has interaction with ________ and __________. How?
- water: absorbs much CO2
- Limestone: deposits of CaCO3 (calcium carbonate)
how much of nitrogen is in the atmosphere and in what form?
80% in atmosphere (as N2) (nitrogen gas)
where is nitrogen found in our body?
in DNA and proteins
Plants can't use N2, what do they use?
what is nitrogen fixation? how is this done?
- converting nitrogen gas into ammonia (N2 ---> NH3)
- by bacteria (terrestrial), cyanobacteria (aquatic), lightening and fertilizers
what is nitrification? how is this done?
- converting ammonia to nitrate (NH3--->NO3-)
- by bacteria in root nodules, like in legumes
what is denitrification? How is this done?
- converting nitrate back to nitrogen gas (NO3- --->N2)
- by anaerobic bacteria
why is phosphorous need?
for a greater importance in inorganic reservoirs
where is phosphorous found in the body?
phospholipids and ATP
what is the nitrogen cycle? (5)
- plants/animals decomposed by decomposers
- ammonification into ammonium (NH4+)
- Nitrification by nitrifying bacteria
- denitrification by denitrifying bacteria
- nitrogen gas in atmosphere
what is the phosphorous cycle? (7)
- rain causes weathering of phosphate from rocks
- phosphate in soil
- phosphate in solution (water); detritus settling to bottom
- sedimentation=new rocks
- geologic uplifting (mountains)
why is chemical cycling faster in the tropics?
more heat for reactions
In tropical rainforest, how is nutrients distributed?
- ~10% of nutrients in soil
- ~75% in tree trunks
In temperate forest, how is nutrients distributed?
~50% of nutrients in soil
what are the 9 human impacts on the ecosystem?
- nutrient runoff can be increased by clearing land
- nutrient enrichment
- acid rain
- toxins in environment
- rising CO2 levels
- depletion of atmosphere ozone (O3)
- Habitat destruction and fragmentation
- resource depletion
- spreading invasive exotic species
From where do nutrients runoff into water bodies? (3) what is this called?
- from fertilized or burned fields
- called cultural eutrophication
Why is nitrogen and phosphorous important?
because they're usually limiting primary productivity
about how much of the Nitrogen fertilizer given to crops, taken up by plants?
what is acid rain due to?
- due to burning of fossil fuels
- and coal because not pure carbon (S & N)
How are toxins found in environment? (2)
- we release thousands of compounds
- some are metabolized; other accumulate in tissues
what is rising carbon dioxide levels due to? where is it mainly from?
- due to increased burning of fossil fuels
- cellular respiration and volcanoes produce ~20x more CO2 than human but our contribution is adding up
rising CO2 levels are correlated with ________________________.
CO2 acts as a __________________ gas.
- Rising global temperatures
- greenhouse gas
How will CO2 levels rising affect life? (3)
- change species distribution (extinction?)
- affect agriculture
- acidification of the oceans
what is the function of the ozone and how is it destroyed? what are the possible effect depletion of ozone layer?(2)
- absorbs harmful UV wavelengths
- destroyed by catalytic effect of CFC's
- increased skin cancer rates
- damage to phytoplankton (that do photosynthesis)
humans have modifies how much of earth's land surface? what have they altered? How is this dangerous?
- >50% of earth's land surface
- have altered water and nutrient cycle
- altered habitats may favour spread of disease
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