Ecosystem
• all the organisms
living in a
community, ___
_______________
_______________
_______________
_______________
_______________
_______________
Energy Flow and Chemical Recycling
• Energy flows through
ecosystems, _______
__________________
__________________
__________________
__________________
Energy Flow
• Energy: the ability to do work
• Behavior describe by:
• 1st Law of Thermodynamics
_______________________________________
_____________________________________________
_____________________________________________
_____________________________________________
2nd Law of Thermodynamics
_______________________________________
_____________________________________________
_____________________________________________
_____________________________________________
This means….
With the passage of time, ____________tend to
move toward maximum _________,
eventually no energy available to do work.
But…
Living systems, like us, are ____________with
a constant input of energy.
Energy, Mass, and Trophic Levels
• Energy in
– from the Sun
– captured by _________
= ____________
• Energy through
– food chain
• transfer of energy
from autotrophs to
_____________________
(herbivores to
carnivores)
• heterotrophs =
_____________________
– herbivores
– carnivores
2005-2006
Figure 42.4
Sun
Key
Chemical cycling
Energy flow
Heat
Primary producers
Primary
consumers
Secondary and
tertiary
consumers
Detritus
Microorganisms
and other
detritivores
Figure 42.3
Detritivores, or
decomposers, are
consumers that
________________
________________
________________
_______________.
Prokaryotes and
fungi are important
detritivores.
Primary Production
• The ___________________converted to
_____________by an ecosystem’s autotrophs
in a given _____________.
• Sets the budget for the ecosystem.
• Only ____of the energy striking the earth is
converted to chemical energy.
Gross and Net Primary Production
– Total primary production is known as gross
primary production (GPP).
• This is the ________________that is converted into
________________in an ecosystem.
– The net primary production (NPP) is equal to
_________________minus the ___________by
the primary producers for _____________(R):
• NPP = GPP – Ra
• NPP is expressed as
– Energy per unit area per unit time (J/m2  yr), or
– Biomass added per unit area per unit time
(g/m2  yr)
• Net ecosystem production (NEP) is a measure of
the _____________________________during a
given period
• NEP is gross primary production minus the total
respiration of all organisms (producers and
consumers) in an ecosystem (RT)
NEP = GPP − RT
Figure 42.6
Where are the most productive areas on Earth?
Net primary production
(kg carbon/m2 • yr)
3
2
1
0
What do you notice about Primary Production in the Oceans?
In aquatic ecosystems, light and nutrients limit
primary production
• Production in Marine
ecosystems.
– Light is the first
variable to control
primary production
in oceans, since
____________________
____________________
____________________
_________(photic zone).
2005-2006
•In the open ocean, nitrogen and
phosphorous levels are very low
in the photic zone, but high in
deeper water where light does
not penetrate.
Phytoplankton density
(millions of cells per mL)
Which nutrient limits phytoplankton?
30
Ammonium
enriched
24
Phosphate
enriched
18
Unenriched
control
Ecologists use the term limiting
nutrient to define the nutrient that
must be added for production to
increase.
12
6
0
A
B
C
D
E
Collection site
F
G
• Upwelling of nutrient-rich waters in parts of the
oceans contributes to regions of high primary
production
• Production in Freshwater Ecosystems.
– ________________________________
are closely linked to primary production
in freshwater lakes.
– During the 1970s, sewage and fertilizer
pollution added nutrients to lakes,
which shifted many lakes from having
phytoplankton communities dominated
by cyanobacteria.
2005-2006
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• This process is
called
_______________,
and which can
lead to
loss of most fish
species
2005-2006
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Primary Production in Terrestrial Ecosystems
• In terrestrial ecosystems, _______________ and
__________ affect primary production on a large
scale
• Primary production increases with moisture
Figure 42.8
Net annual primary production
(above ground, dry g/m2 • yr)
1,400
1,200
1,000
800
600
400
200
0
20
40
60
80
100 120 140 160 180 200
Mean annual precipitation (cm)
• Actual evapotranspiration is the ____________
____________and evaporated from a landscape
• It is affected by ____________, _____________,
and ____________ energy
• Actual evapotranspiration can be used as a
predictor of net primary production
• ______________are often the limiting factors
in primary production (__________________
______________)
– adaptations help plants access limiting nutrients
from soil.
• ___________________
• mycorrhizal fungi
– these fungi _____________
__________and other limiting
elements
• Roots have root hairs that
increase _______________
• Many plants release enzymes
that increase _____________
_____________________
• Secondary production of an ecosystem is the
amount of ____________in food converted to
______________during a given period of time
Net secondary production is
the energy stored in
biomass
An organism’s production
efficiency is the ________
__________that is not
used for _____________.
Energy transfer between trophic levels is
typically only _____efficient
Trophic structure
• Food chains
– feeding relationships
– food chain usually 4
or 5 links = ________
_____________
– length of food chain
limited by _________
___________________
___________________
2005-2006
Why are big, fierce animals rare?
The nitrogen cycle
The phosphorous cycle
The carbon cycle
The water cycle