chapter 20 Flashcards
provides energy to the ecosystem.
Primary productivity
The movement of energy depends on
the efficiency of energy flow.
Most energy that moves through ecosystems originates as
solar energy that powers photosynthesis.
Where sunlight is not available (e.g., deep ocean thermal vents), producers rely on
on chemosynthesis as their source of energy.
Producers use energy for
respiration, growth, and reproduction.
the rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis.
Primary productivity
The difference between gross primary productivity (GPP) & NPP (Net PP) is due to
the energy lost to respiration.
the biomass of producers present in a given area of an ecosystem at a particular moment in time
Standing crop
the rate at which energy is captured and assimilated by producers in an area.
Gross primary productivity (GPP):
the rate of energy that is assimilated by producers and converted into producer biomass in an area; includes all energy that is not respired:
Net primary productivity (NPP
net primary productivity equation
NPP = GPP - Respiration
gross primary productivity equation
GPP = NPP + Respiration
respiration equation
Respiration = GPP - NPP
is photosynthesis an efficient process
no
can be measured as the change in producer biomass over time
NPP
Substantial amounts of herbivory or tissue mortality will lead to
an underestimation of NPP.
Since producers take up CO2 during photosynthesis and produce CO2 during respiration
we can measure NPP by recording the rate of CO2 exchange from the leaf
what happens When a leaf is concealed in the dark
only CO2 respiration occurs.
Other techniques used to measure CO2 uptake and release
- place a leaf into a sealed container with added CO2 that contains trace amounts of a rare carbon isotope
- researchers measure CO2 uptake and release by using towers that sample CO2 concentrations at different heights above the ground.
measuring CO2 does not provide a good estimate of NPP because CO2 is rapidly converted into bicarbonate ions in what systems?
aquatic systems
Since producers release O2 during photosynthesis and take up O2 during respiration
we can estimate NPP and GPP by measuring changes in concentrations of O2.
In a bottle exposed to light, the net increase in O2 is the combined result of photosynthesis and respiration by
algae (NPP).
In a dark bottle, the decrease in O2 is a result of
algal respiration.
a technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.
Remote sensing
high absorption of blue and red light, and high reflectance of green light indicate
ecosystems with high standing crops.
the portion of consumed energy that is excreted or regurgitated.
Egested energy
the portion of energy that a consumer digests and absorbs; analogous to GPP for producers.
Assimilated energy
the portion of assimilated energy a consumer uses for respiration
Respired energy
the rate of consumer biomass accumulation in a given area
Net secondary productivity
Net secondary productivity depends on
primary productivity for energy
increases in NPP are positively correlated with
increases in net secondary productivity.
At higher latitudes, productivity is limited by
shorter periods of sunlight and lower temperatures
In deserts, NPP is constrained by
lack of precipitation.
Tropical areas have high NPP due to
intense sunlight, warm temperatures, abundant precipitation, and rapidly recycled nutrients.
Ecosystems that receive more than 3 m of precipitation experience a decline in NPP because
nutrients leach from the soil.
Rates of decomposition are reduced in
waterlogged soils.
Grasslands, forests, and tundra habitats all experienced increased NPP when
nitrogen and phosphorus were added.
In addition to temperature, precipitation, and nutrients, aquatic ecosystems are also limited by
light.
Within aquatic ecosystems that have similar temperatures and light levels
NPP is largely limited by nutrients
Diatoms are often limited by
by silicon and iron
chart composed of stacked rectangles representing the amount of energy (i.e., pyramid of energy) or biomass (i.e., pyramid of biomass) in each trophic group.
Trophic pyramid
and only small amounts of terrestrial plant material are consumed in what systems
terrestrial systems
most producers are tiny algae that rapidly reproduce and are quickly consumed in what ecosystems
aquatic ecosystems
creates an inverted biomass pyramid.
standing crop of algae is much smaller than that of consumers
the percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level
Consumption efficiency
the percentage of consumed energy that is assimilated (i.e., material that is not egested, such as bones).
Assimilation efficiency
primary consumers tend to have lower efficiencies than secondary consumers
because prey tissues are more digestible than plant tissues.
the percentage of assimilated energy that is used for growth and reproduction; the percentage of assimilated energy that remains after respiration.
Net production efficiency
net production efficiency can be as low as 1%.for what type of animals
active homeothermic animals
active homeothermic animals spend energy to
maintain body temperature, move, circulate blood, and osmoregulate
net production efficiency can be as high as 75%.
For sedentary poikilothermic animals
the percentage of net production from one trophic level compared to the next lower trophic level.
Ecological efficiency (food chain efficiency):
the percentage of net production from one trophic level compared to the next lower trophic level.
Ecological efficiency (food chain efficiency):
ecological efficiency is usually low, ranging from
5% to 20%;
10% is used as a rule of thumb for
ecological efficiency
Low ecological efficiencies make it difficult to have long food chains because
there is little energy to support higher trophic levels
how many trophic levels fo aquatic ecosystems typically have
5
how many trophic levels do terrestrial ecosystems usually have
3-4
terrestrial plants are not easily consumed because
they contain defense compounds
aquatic algae is easily consumed because
they are small and have no defenses
the length of time that energy spends in a given trophic level; the longer the residence time, the greater the accumulation of energy in that trophic level
Energy residence time
the length of time that biomass spends in a given trophic level.
Biomass residence time
Average residence times for primary producers range from
more than 20 years in forests to less than 20 days in aquatic ecosystems.
the study of the balance of nutrients in ecological interactions, such as between an herbivore and a plant.
Ecological stoichiometry
