2.5 ecosystem functions. major functions of an ecosystem producers-convert sunlight energy into...
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2.5 Ecosystem Functions
Major Functions of An Ecosystem
Producers-Convert sunlight energy into organic matter
Consumers- Use living organic matter as energy to grow and develop
Decomposers- Break down the dead organic matter / return nutrients to the soil
ENERGY ENTERS THE ECOSYSTEM AS SUNLIGHT
Only 2% of the light energy falling on plant is used to create energy
The rest is reflected, or just warms up the plant as it is absorbed
Photosynthesis Process where plants use sun light
energy to create chemical energyPhotosynthesis: equation
◦6CO2 + 6H2O --> C6H12O6 + 6O2
Inputs: light energy, water, carbon dioxide
Outputs: oxygen gas, sugarEnergy transformations: Light to
Chemicalrespiration backwards!
RespirationProcess by which animals create energy
through consumption of organic molecules (sugars)
Respiration: ◦C6H12O6 + 6O2 --> 6CO2 + 6H2O
Inputs: oxygen gas, organic molecules (sugars)
Outputs: carbon dioxide, energy in ATP, waste heat
Energy transformations: chemical to heat
Photosynthesis backwards!
Photosynthesis and Respiration
Glucose / Oxygen
CO2/ Water
Energy Transfers in Ecosystem
Energy Flow Diagram
Water Cycle
Nitrogen Cycle
Carbon Cycle
Gross productivityTotal energy captured or
“assimilated” by an organism.
Measured in joules (J)Plant (Gross Primary
Productivity)◦ GPP = sunlight energy used
during photosynthesisAnimals (Gross
Secondary Productivity)◦ GSP = food eaten - energy
in faeces
Energy is stored in leaf as sugars and starches, which later are used to form flowers, fruits, seeds,
Net productivity The energy left over after organisms have
used what they need to survive.All organisms have waste energy and
respiratory loss given off as heat, metabolism (R)
Plants and animals have to use some of the energy they capture to keep themselves growing:◦ They both move water and stored chemicals around◦ Plants make flowers, fruits, new leaves, cells and
stems◦ Animals create cells and need to move muscles.
Net productivity = Gross productivity - Respiration Energy
or using symbols: NP = GP - R
Net Primary vs. Net Secondary Productivity (NPP) vs. (NSP)
Calculate Net productivity for plants and animals NPP = GPP – R PLANTS NSP = GSP – R ANIMALS
NSP
GSP
Productivity in Food WebIn a food web diagram, you can assume
that:◦ Energy input into an organism represents the GP◦ Energy output from that organism to the next
trophic level represents the NP◦ GP-NP = R (respiration energy ) and/or loss to
decomposers
?
Therefore…
The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients.◦Example biome:_______________
The most productive ecosystems are those with high temperature, lots of water light and nutrients.◦Example biome:__________________
Now check you have understood!
Draw a complete food web for an ecosystem of your choice, which should include:◦ the sun and its energy◦ named primary producers (at least 2)◦ named primary consumers (at least 3)◦ named secondary consumers (at least 2)◦ named decomposers (at least 2)◦ respiration energy loss (use red marker for this
arrow)On your diagram use arrows to show
direction of energy flow
◦ Complete this energy flow diagram: Label GPP, NPP and R for the primary
producer Add arrows to show missing energy pathways
(5 in total) Fill in the blank box to explain why some
sunlight is not fixed by plantSUN PLANT
DECOMPOSERS
RESPIRATION…………………………….(~98% of energy is here)
HERBIVORES
Draw your own energy flow diagram, rather like the one on the previous slide to show energy flows through the trophic levels in your food web. Include the following labels:◦ Start with sunlight energy◦ Include all trophic levels from your food web◦ Include arrows showing energy moving from each
trophic level to another and to decomposers◦ Show energy lost in faeces◦ Show Respiration loss (heat energy) USE RED
MARKER!◦ Label each individual arrow with a letter
(A,B,C,D,E…)◦ Use the lettered arrows to write an equation for GPP,
NPP◦ Write an equation for GSP, NSP for primary
consumers
The data in the table below relate to the transfer of energy in a small clearly defined habitat. The units in each case are in kJ m-2 yr-1
Construct an energy flow model to represent all these data Calculate the Net Productivity for
◦ Producers◦ Consumers◦ Decomposers
Trophic LevelGross
ProductionRespiratory
LossLoss to
decomposers
Producers 60724 36120 477
Herbivores 21762 14700 3072
First Carnivores 714 576 42
Top Carnivores 7 4 1
Respiratory loss by decomposers
--- 3120 ---
Producers Herbivores1st.
CarnivoresTop
Carnivores
Decomposers
60724
R=36120
477
21762
R=14700
3072
714
R=576
42
7
R=4
1
R=3120
ENERGY FLOW MODEL
NPP of Producers:60724 -(36120+477)=24127 kJ.m-2.yr-1
NSP of Herbivores:21762-(14700+3072)=3990 kJ.m-2.yr-1
NSP of Decomposers:(477+3072+42+1)-3120=472 kJ.m-2.yr-1
Calculations:
NSP of Herbivores:714 -(576+42) =96 kJ.m-2.yr-1
NSP of Herbivores:7 -(4+1) =2 kJ.m-2.yr-1
NSP of Consumers:22483
-(15280+3115)=4088 kJ.m-2.yr-1
Question:
How to measure primary productivity
1. Harvest method – measure biomass and express as biomass per unit area per unit time.
2. CO2 assimilation- measure CO2 uptake in photosynthesis and releases by respiration
3. 02 production-Measure O2 production and consumption
Measuring productivity continued4.Radiosotope method-use c14 tracer
in photosynthesis.5.Chlorophyl measurement- assumes
a correlation between the amount of chlorophyll and rate of photosynthesis.