Ecosystems and Global Ecology Flashcards
what are autotrophs
Primary producers, can synthesize food from inorganic sources
Form the basis of ecosystems by transforming the energy in sunlight into the chemical energy stored in sugars
whats Gross primary productivity (GPP)
total chemical energy produced in a given area and time
how do primary producers use chemical energy
Cellular respiration: energy just to stay alive
Growth and reproduction: in primary producers, this energy is called net primary productivity (NPP)
how efficient are autotrophs
very inefficients, Only ~0.8% of incoming sunlight is captured by plants (solar panels capture 22%)
Only ~45% of GPP went into production of new biomass other 55% was used for respiration or was lost
why are autotrophs inefficient
- Pigements absorbed only a fraction of light wavelengths available
- Photosynthetic rates in temperate biomes are drastically reduced in winter (efficiency of enzymes is temperature dependant)
- In dry conditions, stomata close and photosynthesis stalls
define productivity
a rate, its the biomass produced each year (g/m^2/year)
define efficiency
a ratio, fraction of biomass transferred from one trophic level to the next.
Efficiency ~10% but can vary dramatically.
The 10% rule masks interesting variation
Eg: ectotherms more efficient biomass producers than endotherms
what are the steps to biomagnification
- Pollutant taken up by primary producers
- Primary consumers cannot metabolize or excrete pollutant. Only ~10% of primary biomass incoporated into consumer biomass, but all the pollutanta are retained (tenfold increase in concentration)
3 .Same process occurs in secondary consumers, causing another tenfold increase - And so one; the more trophic levels there are in a food web, the higher the biomagnification
what is biomagnification
The increase in concentration of a toxic substance as it moves up the food chain.
is NPP higher on land or sea
NPP on land higher then see
More light available for photosynthesis
Water quickly absorbs many wavelengths of light. Terrestrial ecosystems with high productivity are in tropics
Except for major deserts, NPP on land decline towards poles
in terms of NPP what is the ocean compared to
the desert
what is the biogeochemical cycle
- Nutrients taken up from soil by plants
- If plant is eaten, nutrients pass to consumers
- If plant dies, nutrients pass to decomposers
Factors that control rate of nutrient cycling
- Abiotic conditions (eg; oxygen availability, temp, precipitation)
- Quality of detritus (organic matter) as a nutrient source for fungi, bacteria
- Abundance and diversity of detritivores
