19: Primary and Secondary Production & Energy Flow Flashcards
With the exception of a few ecosystems, this fuels life on earth:
primary production through photosynthesis
The flow of energy through a system starts with what?
harnessing energy from sunlight
The total rate of photosynthesis or total amount of energy assimilated by autotrophs.
Gross Primary Production (GPP)
The rate of energy storage or amount of energy stored after respiration.
Net Primary Production (NPP)
NPP=GPP-R
Net Primary Production = Gross Primary Production - Respiration
Glucose produced during photosynthesis
GPP
Some glucose used to supply energy to drive cellular processes.
Respiration
Remaining glucose available to be laid down as new material - biomass
NPP
Why do we care about NPP at the individual and population levels?
NPP represents plant growth and health
Why do we care about NPP at the community and ecosystem levels?
NPP represents the amount of C (or food) available at the base of the food web, and thus all trophic levels.
Why do we care about NPP at the ecosystem, biome, and biosphere levels?
NPP represents the amount of C that is stored in plant biomass
How do we measure NPP in AQUATIC ecosystems?
Light – dark bottle technique
What processes take place within the light (transparent) bottle?
Photosynthesis + Respiration (R)
What processes take place within the dark (opaque) bottle?
Only respiration (R)
What do we measure in the Light-Dark Bottle Technique?
Measure change in 02 in each bottle over some set time (generally over 24 hrs)
Light-Dark Bottle Technique equation
NPP + R = GPP
Amount of O2 produced in photosynthesis and 02 used in respiration (NPP) + amount of O2 loss (R) = Gross Primary Product (GPP)
In aquatic ecosystems, it is important to get continuous measurements of what?
O2 between day and night
In terrestrial ecosystems, what do we measure to get the NPP & GPP?
CO2
What could be done in a terrestrial ecosystem to estimate NPP?
use Standing Crop Biomass
Amount of accumulated primary producer biomass in a given area at a given time
Standing Crop Biomass
What is the problem with using biomass to estimate NPP?
Productivity (or NPP) is the rate or amount of organic matter created by photosynthesis, whereas biomass is the amount of organic matter present at a given time
How could we measure biomass (or NPP) from space?
By using chlorophyll
How was the use of biomass to estimate NPP influence your results?
You would underestimate NPP
What environmental factors influence productivity in terrestrial ecosystems?
Temperature and precipitation
High temperatures reflects high amounts of solar radiation and longer growing seasons
Therefore solar radiation fuels primary productivity
Global limits on primary production
Temperature, Sunlight, and Water
NPP is highest in what zone, with year-round warm temperatures, high precipitation and higher radiation?
The equatorial zone
How does Earth’s tilt influence temperature?
23.5° on axis. Energy from the sun does not reach all areas of the earth with equal strength. Areas near the equator receive direct an intense solar energy, which influences temperature.
Why is NPP reduced as you move north or south on the globe?
Cooler temperatures, and higher seasonal variation in temperatures and precipitation, less direct radiation
How does tilt influence sunlight intensity?
Intense Solar Energy: Light hits directly and it spread over a small area. Less Solar Energy: light hits at an angle and is spread over a larger area at higher latitudes
Sunlight is more diffuse and takes a longer path through the atmosphere at higher latitudes
These areas receive less solar energy
How does NPP change?
Seasonally and annually
Which of the following biomes do you expect to have the lowest NPP and why? Boreal forest, temperate forest, tropical forest, or tundra
Tundra, due to low precipitation and temperatures
How does nutrient availability influence NPP?
Adding fertilizers nearly doubled primary production in these tundra study plots
In the Oceans, why is 80% of light absorbed in the first 10 m, and why is the Euphotic Zone down to 200 m?
Vertical structuring of the oceans leads to variations in light with depth.
In the oceans, absorbed solar energy increases kinetic energy, which increases temperature, but why is the warm water that floats on top the cold water separated by a thermocline?
Vertical structuring of the oceans leads to variation in temperature with depth
In the deep ocean where does primary production take place?
It is located near the surface
Euphotic Zone (ocean)
Sunlight Zone, sunlight rarely penetrates beyond this zone.
Dysphotic Zone (ocean)
Twilight Zone, sunlight decreases rapidly with depth. Photosynthesis is not possible here.
Aphotic Zone (ocean)
Midnight Zone, sunlight does not penetrate at all. This is zone is bathed in darkness.
Epilimnion Zone (Lakes)
Sunlight penetrates and warms the water
Metalimnion (Lakes)
Temperature and other physical and chemical factors change rapidly with depth
Hypolimnion (Lakes)
Water is cold and dark and may lack dissolved oxygen
What influences aquatic primary production?
Nutrients
Why do we care about primary production?
Represents plant growth and health. Is the base food for nearly all food webs. The amount of C stored in primary production influences the C cycle.
The rate at which consumers convert the chemical energy of their food into their own biomass.
Secondary production
What limits secondary production?
Primary production
When would secondary production likely be greatest?
When birthrate of the population is highest. When growth rates of individuals is highest. When primary productivity is highest.
Efficiency with which the consumer extracts energy from food
Assimilation efficiency
Assimilation efficiency equation
Assimilation efficiency = Energy is assimilated across the gut wall (A)/ food ingested (I)
Measures how efficient the consumer is at incorporating assimilated energy into secondary production
Production efficiency
Production efficiency equation
Production efficiency = production or growth (P)/ Energy assimilated across the gut wall(A)
Consumers vary in their ability to extract energy from their food. At the individual and population level? At the community and ecosystem level? At the ecosystem, landscape, and biosphere level?
Individual and population level: growth and fecundity of the heterotroph. Community and ecosystem level: amount of energy available to the next trophic level. Ecosystem, landscape, and biosphere level: nutrients recycled in their feces
Production efficiency across taxonomic class varies.
Invertebrates= 30 to 40%. Ectotherm vertebrates= ~ 10%. Endotherm vertebrates= 1 to 2%
Transfer of energy across trophic levels
Energy is lost from one trophic level to the next (~90%). 1,000,000J Sunlight > 10,000J primary producers > 1,000J primary consumers > 100J secondary consumers > 10J tertiary consumers
Standing stock of biomass in a terrestrial ecosystem
Upright pyramid: top carnivore (1kg)
Standing stock of biomass in an aquatic ecosystem
Inverted pyramid: carnivore (12gm/m^2)> herbivores(8gm/m^2)> producers(4gm/m^2)
What causes the inverted pyramid of the standing stock of biomass in an aquatic ecosystems?
Results from small biomasses primary producers, high grazing rates, and fast lifecycles of primary producers
Which of the following biomes do you expect to have the lowest secondary productions? Boreal forest, temperate forest, tropical forest, or tundra
Tundra, because it has the lowest primary production (which is the limiting factor to secondary production)
