Download 2.3.1 Flows of Energy and Matter

2.3.1 Flows of Energy
and Matter
Transfer and transformation of
Energy

Not all solar
radiation ends up as
biomass. Losses
include:
◦ Reflection from leaves
◦ Not hitting
chloroplasts
◦ Wrong wavelength
◦ Transmission of light
through the leaf
◦ Inefficiency of
photosynthesis
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

Transfer and transformation of
energy.

Energy comes into
the ecosystem as
light energy,
Transfer and transformation of
energy.

Energy converted
into chemical energy
by producers.
Transfer and transformation of
energy.

That chemical energy is transferred as
organisms are eaten, with energy being
lost as heat and respiration.
Photosynthesis
Process where plants use sun light energy to
create chemical energy
 Photosynthesis: equation

◦ 6CO2 + 6H2O --> C6H12O6 + 6O2
Inputs: light energy, water, carbon dioxide
 Outputs: oxygen gas, sugar
 Energy transformations: Light to Chemical
 respiration backwards!

Respiration
Process 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!

Energy Transfers in Ecosystem
Energy Flow Diagram
Conversion of Energy

Conversation of energy into biomass for
a given period of time is measured as
productivity
Gross productivity
Total energy captured or
“assimilated” by an organism.
 Measured in joules (J)
 Plant (Gross Primary Productivity)

◦ GPP = sunlight energy used during
photosynthesis

Animals (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)

Net productivity

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

Primary Productivity – gain by autotrophs
in energy or biomass per unit area per
unit time
Productivity

Secondary Productivity – biomass gained
by heterotrophs thru feeding and
absorption, measured in units of mass or
energy per unit area per unit time
Productivity

Gross Primary Productivity – Gain in
energy or biomass thru photosynthesis
per unit area per unit time.
Productivity

Net Primary Productivity – The gain by
producers in energy or biomass per unit
area per unit time remaining after
respiration losses.
Productivity

Gross Secondary Productivity (Gross
Assimilation) – Gain in energy or biomass
thru absorption per unit area per unit
time.
Productivity

Net Secondary Productivity (Net
Assimilation) – The gain by consumers in
energy or biomass per unit area per unit
time remaining after respiration losses.
Productivity in Food Web

In 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:__________________
How to measure primary
productivity
1.
2.
3.
Harvest method – measure biomass and
express as biomass per unit area per unit
time.
CO2 assimilation- measure CO2 uptake
in photosynthesis and releases by
respiration
O2 production-Measure O2 production
and consumption
Measuring productivity continued
4.Radiosotope method-use c14 tracer in
photosynthesis.
5.Chlorophyl measurement- assumes a
correlation between the amount of
chlorophyll and rate of photosynthesis.
◦ 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 plant
HERBIVORES
PLANT
SUN
………………
…………….
(~98% of energy
is here)
RESPIRATION
DECOMPOSERS
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



Trophic Level
Gross
Production
Respiratory
Loss
Loss to
decomposers
Producers
60724
36120
477
1° Consumer
21762
14700
3072
2° Consumer
714
576
42
3° Consumer
7
4
1
Respiratory loss
by decomposers
---
3120
---
Construct an energy flow model to represent all these data – Label each arrow with the
appropriate amount from the data table above.
Use boxes to represent each trophic level and arrows to show the flow of energy
Calculate the Net Productivity for
◦ NPP for Producers
◦ NSP for 1°Consumers, 2°Consumers, 3°Consumers
◦ NSP for Decomposers
ENERGY FLOW MODEL
R=36120
60724
Producers
R=576
R=14700
21762
1 Consumer
714
2 Consumer
3072
R=4
7
3 Consumer
42
477
1
Decomposers
R=3120
Productivity Calculations
NPP of Producers:60724 - (36120+477)
NSP of 1 Consumer21762 -(14700+3072)
NSP of 2 Consumer714 -(576+42)
NSP of 3 Consumer7 -(4+1)
NSP of Consumers:
22483 -(15280+3115)
NSP of Decomposers:
(477+3072+42+1)
=24127 kJ.m-2.yr-1
=3990 kJ.m-2.yr-1
=96 kJ.m-2.yr-1
=2 kJ.m-2.yr-1
=4088 kJ.m-2.yr-1
-3120
=472 kJ.m-2.yr-1